Monday, April 5, 2021

“Time Slows Down Whenever You Are Around” for Women but Not for Men

“Time Slows Down Whenever You Are Around” for Women but Not for Men. Joana Arantes et al. Front. Psychol., April 6 2021 |

Abstract: What happens when we unexpectedly see an attractive potential partner? Previous studies in laboratory settings suggest that the visualization of attractive and unattractive photographs influences the perception of time. The major aim of this research is to study time perception and attraction in a realistic social scenario, by investigating if changes in subjective time measured during a speed dating are associated with attraction. The duration of the dates was variable and participants had to estimate the time that passed. Among other measures, participants also rated the potential partners in terms of their physical attractiveness before and after the dates and reported if they would like to exchange contact with them. Results showed that, in a real speed dating situation, when there is a perception of the partner as being physically more attractive, women tend to overestimate the duration of that meeting, whereas men tend to underestimate its duration. Such changes may reflect evolutionary adaptations which make the human cognitive system more responsive in situations related to reproductive fitness.


The main objective of this research was to study time perception and attraction in a realistic social scenario by investigating if changes in subjective time measured during a speed dating session were related with attraction. The duration of the dates was variable and participants had to estimate the time that passed. Participants were asked to rate potential partners in terms of their physical attractiveness before and after the dates and to report if they wanted to exchange contacts with them. Our data suggest, consistently with our hypotheses, that the estimated time of the dates were associated with the physical attractiveness of the potential partners perceived by participants.

More specifically, our results showed that the more females rated a potential partner as physically attractive, the longer they perceived the duration of the date. That goes along with the popular idea that “time slows down whenever you are around” (Swift, 2010). This may be due to a bigger allocation of women’s cognitive resources to process more information of the meeting (Loftus et al., 1987) and of the potential partner they are interested in. More specifically, even though physical attractiveness is important in a potential partner, for women there are other characteristics that may have a higher value, such as good economic prospects (Buss and Barnes, 1986Bech-Sørensen and Pollet, 2016). Therefore, searching for cues of positive traits in a potential mate requires the use of cognitive resources. Besides that, research has shown that when women perceive the partner as attractive, they tend to be more motivated to make a good impression on the partner and pay more attention to the things they say that might influence this impression (Dong and Wyer, 2014). According to Ornstein’s storage size model (Ornstein, 1969Sasaki and Yamada, 2017), when people store more information in memory, they tend to perceive the duration of that interval of time as being longer. Furthermore, women may consider the experience with a partner who they consider physically attractive as positive in an emotional way. This result is also consistent with that study of Kellaris and Kent (1992) in which time did seems to slow downs when participants were exposed to positively valenced music, compared to participants exposed to negatively valenced music. The authors suggested that when people receive positive emotional information they tend to invest more cognitive resources in listening to music. Therefore, they tend to perceive the received stimulus information as larger and remember the event as being longer. Besides that, a study conducted by Zhang et al. (2017) showed a reliable sex differences in temporal distortion with an emotional stimulus. Women, compared to men, tended to overestimate the durations of emotional words.

However, for men, our results showed that time does not seems to slow down whenever someone attractive is around. In fact, the more males rated a female participant as physically attractive, the shorter they perceived the duration of the speed date. This seems to be consistent with the idea that “time flies when you are having fun.” Research has shown that men’s preferences for potential mates are based mostly in physical attractiveness (Lippa, 2007Todd et al., 2007Eastwick et al., 2011). Therefore, when they have a meeting with a potential partner that they perceive as being physically attractive, they do not need to spend much cognitive resources searching for other cues, feeling automatically motivated to be with her. Consequently, they will tend to estimate the time that passed as being shorter. This result also suggests that time perception in males during the dates may be affected by motivation because, according to previous literature, positive approach motivation causes the perception of time to be shorter (Glabe and Poole, 2012). Besides that, the subjective perception of the passage of time seems to be an important component to evaluate the experience of boredom (Danckert and Allman, 2005). So, when males are interested and motivated in the date with a physical attractive potential partner, they tend to estimate the date duration as shorter and, on the other hand, this time underestimation reinforces the perception of an interesting date (Sackett et al., 2010). Underestimation of the duration of the date may prolong approach-motivated behavior (Glabe and Poole, 2012) and this increases the probability of a successful mating. On time, Einstein said “Put your hand on a hot stove for a minute and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute.”

According to Trivers’ (1972) theory, the relative parental investment of the sexes in their offspring is the key variable controlling the operation of sexual selection. Sexual intercourse for a male is a small investment, but for a female can produce a 9-month investment, at least. For a female, this investment requires more choosiness in the partner choice. Besides that, prior research showed that females tend to be more selective (Kurzban and Weeden, 2005) and more discriminating (Todd et al., 2007) than males. Therefore, it is expected that females allocate more attention to capturing a greater number of characteristics of the potential partner in addition to physical attractiveness, such as intelligence, personality, earning prospects and other signs suggesting he could be good partner in the future. This process seems to imply an exhaustive evaluation in the first meeting which requires the allocation of a lot of cognitive resources. On the other hand, men are attracted by fewer characteristics of the partner compared to females (Luo and Zhang, 2009). So, males do not use so much energy and resources in cognitive processing of information and focus more energy in having fun with the partners they perceived as being more attractive. Such changes may reflect evolutionary adaptations which make the human cognitive system more responsive in situations related to reproductive fitness.

Williams (2012) suggested that sex differences in timing might be due to the effects of circulating estrogen in adult females versus testosterone in adult males. Besides that, gonadal hormones had been found to influence sexual motivation (Wallen, 2001). In men, testosterone increases interest in a woman, engagement in self-presentation, smiling and making eye contact (Roney et al., 2006Meij et al., 2011Thornhill et al., 2013). Meij et al. (2011) suggested that during encounters with the opposite sex, testosterone may promote the display of affiliative behaviors that increase a man’s mating prospects and during social contact with a potential partner testosterone is linked to the initiation of courtship behaviors. On the other hand, in women, estradiol seems to be a significant positive predictor of sexual desire (Puts et al., 2013Roney and Simmons, 2013).

Estradiol is one of the natural estrogens and has been shown to increase striatal dopamine release, that may modify temporal perception and timing performance in a manner similar to indirect dopamine agonists such as amphetamine and cocaine (Pleil et al., 2011). Estrogen as a dopamine agonist facilitates striatal dopaminergic activity (Sandstrom, 2007), stimulating the dopaminergic transmission and, consequently, producing an overestimation of time intervals (Cheng et al., 2006). Pleil et al. (2011) investigated sex differences in the rapid and acute effects of estradiol on time perception in adult male and female rats. According to the authors, their results are consistent to the idea that there are multiple mechanisms of estrogen’s action in the striatum that modulate dopaminergic activity and are differentially organized by gonadal steroids during early brain development. Additionally, Becker (1999) found that striatal dopaminergic release is affected by estrogen only in females. The striatum is one of the components of the basal ganglia that have been suggested to be a fundamental component of the neural basis of timing (Ivry and Spencer, 2004) and multiple studies, specifically with patients with dopamine system disorders as Parkinson (Leranth et al., 2000Michel et al., 2002), and schizophrenia (Seeman and Lang, 1990Riecher-Rössler and Häifner, 1993Michel et al., 2002) and others, found an interaction between gonadal steroid hormones such as estrogen in basal ganglia mechanisms (Hartesveldt and Joyce, 1986). Therefore, because of the fact that estrogen is a predictor of sexual desire and sexual motivation, this may increase their circulation in women during a speed date with physically attractive partners and, subsequently, increase dopamine release in striatum. Besides that, some studies found that women, on average, have higher presynaptic dopamine synthesis capacity (Laakso et al., 2002) and lower D2 receptor affinity (Pohjalainen et al., 1998) that suggests an increased endogenous dopamine in women’s striatum, comparing to men. So, neural sex differences in dopaminergic circuits in the striatum could explain this sex difference on the influence of physical attractiveness in time perception. It is thus possible that sexual hormones on males have an opposite effect in striatum (Myers et al., 2003).

Our results may diverge from Dong and Wyer (2014) study because sex differences in their study could be masked by lack of cues in the interaction that could influence attraction mechanisms. Specifically, the reduction of non-verbal information may influence the response of females more than males because, according to a vast literature (Mehrabian, 1972Mehrabian and Ksionzky, 1972Zahn, 19731975), females are more sensitive to non-verbal information and males to a verbal information.

Our study also demonstrates that for the decision of exchanging or not contact with the partner, physical attractiveness seems to be an important factor for both sexes because when participants perceived the partners as physically attractive, they tended to exchange contacts with them. In addition, consistent with our second hypothesis, the physical attractiveness of the potential partner perceived by the participant changes according to the interest in exchanging contact with him/her. In other words, interest or not in the meeting with a potential partner and the desire or not to keep in contact in the future influences their perceived physical attractiveness. Particularly, when participants are interested in a potential partner at the end of the date, they perceive their physical attractiveness as being higher compared to the initial evaluation (i.e., before the date). When participants are not attracted to partners at the end of the date, expressing the desire not to exchange contacts with them, they not change their evaluation of the potential partner’s physical attractiveness. These results suggest that there may be an effect of other characteristics of the potential partner in the evaluation of physical attractiveness. This is supported by some laboratory studies that have shown that the evaluated attractiveness of opposite-sex people is influenced by their personality. For example, Lewandowski et al. (2007) found that when a person was presented with positive personality information about the person shown in a photograph, participants rated that person as more physically attractive and when photographs were paired with negative personality information the person depicted was rated as less physically attractive. These results are also consistent with Kniffin and Wilson’s (2004) naturalistic studies that showed that non-physical characteristics such as familiarity, liking, respect, talent, and effort have a great influence on physical attraction judgments.

Limitations and Future Research

First, previous studies found that preferences in mate selection are influenced by the type of desired relationship, short or long-term. Thus, in future research it seems relevant to question participants in the speed dating event about whether they would like to have a short or long-term relationship with the partners they show an interest in exchanging contacts with. Second, this research shows that in a realistic scenario where two people meet each other, changes occur in time perception and it seems plausible to us that other implicit cognitive processes are affected in this context. However, there are no studies about other implicit measures in speed dating events, such as memory or attention, and future research should focus on this theme. Third, in terms of time perception and attractiveness, our data were correlational, so do not provide evidence for a causal influence of physical attractiveness on timing. Our results suggest that the two variables are associated but it would be interesting to understand if there is a causal relation between them. Third, there were 32 (18.50%) exchanges of contact details but only three intimate relationships were formed and lasted at least 6 months. It would be interest to investigate in future studies which variables have contributed to the development of an intimate relationship after the speed-dating. Fifth, participants were relatively young people, which may represent a limitation of the present study. Research has shown that men tend to prefer females at the age at which fertility peaks in order to increase their reproductive success (Conroy-Beam and Buss, 2019). In future research, it seems important to understand if the results of this study are applicable to older ages, in particular in postmenopausal women. If time perception in dating situations is an adaptive mechanism for mating, this bias should no longer occur in post-reproductive, menopausal women (Cyrus et al., 2011). Finally, our results based on stepwise multiple regression analyses showed that the attraction felt toward the partner was the strongest and unique predictor of both men’s and women’s perceptions of date duration. These results support the idea that when individuals are exposed to opposite-sex persons to whom they feel an attraction, their timing system is affected – women tend to overestimate, whereas men tend to underestimate the passage of time. However, it is still important to notice the weak explanatory power of the models, which indicates that there are other contributing factors to time perception that need to be explored in future research.

Sex differences in brain in response to midlife stress linked to fetal stress exposures

Impact of prenatal maternal cytokine exposure on sex differences in brain circuitry regulating stress in offspring 45 years later. Jill M. Goldstein et al. Proceedings of the National Academy of Sciences, April 13, 2021 118 (15) e2014464118.

Significance: Clinical research and animal models have demonstrated a significant connection between maternal stress during pregnancy and sensitivity to stress in offspring, leading to increased susceptibility to neuropsychiatric disorders later in life. In a unique prenatal cohort that was followed for over four decades, we tested associations between pro- and anti-inflammatory markers in maternal prenatal sera and sex differences in neural responses to negative stress in the offspring in early midlife using functional MRI. Men and women exposed in utero to abnormal levels of pro-inflammatory cytokines and to an imbalance of pro- to anti-inflammatory influences showed dysregulation of stress response circuitry 45 y later, with sex-dependent effects.

Abstract: Stress is associated with numerous chronic diseases, beginning in fetal development with in utero exposures (prenatal stress) impacting offspring’s risk for disorders later in life. In previous studies, we demonstrated adverse maternal in utero immune activity on sex differences in offspring neurodevelopment at age seven and adult risk for major depression and psychoses. Here, we hypothesized that in utero exposure to maternal proinflammatory cytokines has sex-dependent effects on specific brain circuitry regulating stress and immune function in the offspring that are retained across the lifespan. Using a unique prenatal cohort, we tested this hypothesis in 80 adult offspring, equally divided by sex, followed from in utero development to midlife. Functional MRI results showed that exposure to proinflammatory cytokines in utero was significantly associated with sex differences in brain activity and connectivity during response to negative stressful stimuli 45 y later. Lower maternal TNF-α levels were significantly associated with higher hypothalamic activity in both sexes and higher functional connectivity between hypothalamus and anterior cingulate only in men. Higher prenatal levels of IL-6 were significantly associated with higher hippocampal activity in women alone. When examined in relation to the anti-inflammatory effects of IL-10, the ratio TNF-α:IL-10 was associated with sex-dependent effects on hippocampal activity and functional connectivity with the hypothalamus. Collectively, results suggested that adverse levels of maternal in utero proinflammatory cytokines and the balance of pro- to anti-inflammatory cytokines impact brain development of offspring in a sexually dimorphic manner that persists across the lifespan.

Keywords: prenatal immune programmingprenatal stressstress circuitrysexfunctional brain imaging

Press release: Sex differences in brain in response to midlife stress linked to fetal stress exposures --- Exposure to inflammatory substances in the womb due to prenatal stress differentially affects stress circuitry function in male and female offspring, which is retained into midlife.

Naïve, unenculturated chimpanzees fail to make and use flaked stone tools

Naïve, unenculturated chimpanzees fail to make and use flaked stone tools. E Bandini et al. European Human Behaviour and Evolution Association, 15th Conference, Mar 2021.


Objective: Despite extensive research on early hominin lithic technology, the mechanisms underlying flake manufacture and use are still debated. To draw phylogenetic inferences on the potential cognitive processes underlying these abilities in early hominins, we examined whether our closest living relatives, chimpanzees (Pan troglodytes), could learn to make and use flakes.

Methods: We provided naïve unenculturated chimpanzees from two independent populations (n=11) with baited puzzle boxes that could only be accessed with cutting tools, stone cores, and hammerstones to test for their ability to spontaneously make and use flakes.

Results: Despite the fact that the chimpanzees demonstrated an understanding of the requirements of the task and were sufficiently motivated, none of the chimpanzees made or used flakes in any of the experimental conditions.

Conclusions: These results differ from previous ape flaking experiments, which found flake manufacture and use in bonobos and one orangutan. However, these earlier studies tested only enculturated apes and provided them with demonstrations. The contrast between these earlier positive findings and our negative findings (despite using a much larger sample size) suggests that enculturation and/or human demonstrations may be necessary for chimpanzees to acquire these abilities. The data obtained here is consistent with the hypothesis that flake manufacture and use might have evolved in the hominin lineage after the split between Homo and Pan 7 million years ago, a  scenario further supported by the apparent absence of flaked stone tools in the archaeological record after this split.

Intent-based morality in Colombian and Spanish children: Punishment & retribution

Intent-based morality in Colombian and Spanish children. RL Arini et al. European Human Behaviour and Evolution Association, 15th Conference, Mar 2021.


Objective: The majority of the developmental literature about the role of outcomes and intentions in moral evaluations has been conducted on English-speaking children and focused on harm and property transgressions. We aimed at investigating this phenomenon in 5- to 11-year-olds from collectivistic Colombia and individualistic Spain (N=123) employing moral scenarios involving disloyalty and unfairness.

Methods: We developed a computer game showing internet players violate moral norms; children took the role of referees and had the opportunity to judge and punish the players for their behaviour.

Results: Regarding judgements of transgression severity, Colombian children judged failed intentional transgressions more severely than accidental transgressions in case of disloyalty, but not yet in case of unfairness. Regarding punishment severity, Spanish children began to punish failed intentional transgressions of both moral domains more severely than accidents around 8 years of age. While punishment severity decreased with increasing age for both unfairness and disloyalty in Spanish children, in Colombian children the downward pattern was observed only for unfairness. Additionally, children anticipated punishment to feel worse than how it actually felt during and after punishment allocation.

Conclusions: According to cultural group selection, it makes evolutionary sense that children’s sensitivity to intentionality develops earlier within the moral domains (loyalty) privileged by their own (collectivistic) cultures. Moreover, selective concerns for one moral domain (loyalty) over another (fairness) may become more pronounced with development because of culture-directed learning processes. The lack of hedonic punishment expectations suggests that retribution is unlikely to be the primary driver of children’s third-party punishment.

Even though inaccurate beliefs lead to costly mistakes, people interpret favorable feedback to be more informative; author casts a new light on the origins of overconfidence & the mechanisms that perpetuate it in the face of feedback

Belief-Based Utility and Signal Interpretation. Marta Kozakiewicz. February 23, 2021.

Rolf Degen's take:

Abstract: People tend to overestimate their abilities and chances of success, even though inaccurate beliefs lead to costly mistakes. How can these beliefs persist in an environment with frequent feedback? I propose a new test of the hypothesis that people interpret favorable feedback to be more informative. Using experimental data, I provide the first causal evidence that the utility from beliefs affects one’s perception of signal informativeness. To establish causality, I adopt a matching estimator approach and construct a counterfactual outcome of a subject who observes the same signal, but the signal is not affecting his belief-based utility. I find a strong and significant effect: subjects interpret favorable signals to be more informative due to changes in belief-based utility. The results cast a new light on the origins of overconfidence and illuminate mechanisms that perpetuate it in the face of feedback.

Keywords: overconfidence, belief formation, learning, experiment

JEL classification: C91, D83

Claims About The Hidden Cost of Religiosity and the Gender Wage Gap

The Hidden Cost of Prayer: Religiosity and the Gender Wage Gap. Traci Sitzmann and Elizabeth M. Campbell. Academy of Management Journal, Oct 27 2020.

Abstract: Religion is a preeminent social institution that meaningfully shapes cultures. Prevailing theory suggests that it is primarily a benevolent force in business, and differences across world religions preclude examining effects that thread across religions. We develop a theoretical account that fundamentally challenges these assumptions by explaining how and why religiosity—regardless of which religion is prominent—differentiates based on gender, widening the gender wage gap. Guided by an integrated review of the religion literature, we specify three dimensions of gender differentiation—social domains, sexuality, and agency—that explain why religiosity widens the gender wage gap. A series of studies tested our theoretical model. Two studies showcased the predictive power of religiosity on the gender wage gap across 140 countries worldwide and the 50 United States via gender-differentiated social domains, sexuality, and agency, explaining 37% of the variance in the wage gap. U.S. longitudinal data indicated the gender wage gap is narrowing significantly faster in secular states. Moreover, experiments allowed for causal inference, revealing that gender-egalitarian interventions blocked the effect of religiosity on the gender wage gap. Finally, theoretical and empirical evidence converge to suggest that religiosity’s effect on the gender wage gap applies across the major world religions.

Sunday, April 4, 2021

Do EITC expansions pay for themselves? Effects on tax revenue and government transfers

Do EITC expansions pay for themselves? Effects on tax revenue and government transfers. Jacob E. Bastian, Maggie R. Jones. Journal of Public Economics, Volume 196, April 2021, 104355.


• The EITC increases the labor supply of mothers, which leads to increases in payroll and sales taxes paid.

• The EITC decreases dependence on government transfer spending.

• Evaluated over a one-year period, the net EITC cost is only 17 percent of the $70 billion annual budgetary cost.

• Evaluated over a longer-time horizon, the net EITC cost is lower and perhaps zero.

• The 2009 EITC expansion continued to increase maternal labor supply and earnings.

Abstract: This paper calculates the EITC’s net cost by estimating effects, both direct and through recipients’ behavioral changes, on tax revenue and government transfer spending. We show that the EITC increases labor supply and income, thereby increasing the taxes households pay and reducing the government transfer payments they receive. Using linked IRS–CPS data and several EITC policy changes, and focusing on married and unmarried women, we find that the EITC’s net cost is only 17 percent of the ($70 billion) budgetary cost over a one-year period. Although the EITC is one of the U.S.’s largest and most important public assistance programs, the EITC is actually one of the U.S.’s least expensive anti-poverty programs.

Keywords: Earned income tax creditTaxesPublic assistanceGovernment transfersWomen’s labor supplyFiscal policy

The ‘Big Gods Hypothesis’ offered a solution to the origins of religion & of complex societies by proposing that beliefs in moralizing supernatural punishment culturally evolved to facilitate cooperation among strangers

Whitehouse, Harvey, Pieter François, Daniel Hoyer, Kevin C. Feeney, Enrico Cioni, Rosalind Purcell, Robert M. Ross, et al. 2021. “Big Gods Did Not Drive the Rise of Big Societies Throughout World History.” OSF Preprints. April 3. doi:10.31219/

Abstract: The origins of religion and of complex societies represent evolutionary puzzles. The ‘Big Gods Hypothesis’ offers a solution to both puzzles by proposing that beliefs in moralizing supernatural punishment culturally evolved to facilitate cooperation among strangers in large-scale societies. Although previous research has suggested an association between the presence of Big Gods and big societies, the relationship between the two is disputed, and attempts to establish causality have been hampered by limitations in the availability of detailed global longitudinal data. To address these issues, we analyze data in the Seshat Global History Databank that coded 309 past societies for variables capturing beliefs in moralizing supernatural punishment and social complexity. The longitudinal (time-resolved) nature of Seshat data enables us to test evolutionary hypotheses about processes generating social change and distinguish between competing causal scenarios. We find that beliefs in moralizing supernatural punishment only appear after the largest increases in social complexity and that a formal analysis designed to test for causal relationships failed to detect a statistically significant effect of moralizing supernatural punishment on social complexity.

Anxiety sensitivity, female sex, and smoking are risk factors for physical inactivity; high levels of anxiety sensitivity were related to more time spent walking for females but not males

Understanding sex differences in physical activity behavior: The role of anxiety sensitivity. Gloria J. Gomez et al. Mental Health and Physical Activity, March 29 2021, 100392.


• Anxiety sensitivity, female sex, and smoking are risk factors for physical inactivity.

• Higher anxiety sensitivity levels were related to lower total physical activity levels in males.

• Females' total physical activity levels were not dependent on anxiety sensitivity levels.

•High levels of anxiety sensitivity were related to more time spent walking for females but not males.


Problem: There is a well-evidenced sex-disparity in physical activity (PA), such that females are significantly less active than males. Anxiety sensitivity, the fear of anxiety-related bodily sensations, is a cognitive-affective vulnerability associated with increased negative affect during PA and lower levels of PA. The current study examined anxiety sensitivity as a potential sex-specific, psychological factor related to sex differences in past-week PA behavior in daily cigarette smokers.

Method: Participants (n=527; 53.3% female) completed an anonymous online survey on emotion and health. Anxiety sensitivity was assessed with the Anxiety Sensitivity Index-3. Past-week, self-reported PA minutes were measured across four intensities (e.g. walking, moderate, vigorous, and total PA) using the International Physical Activity Questionnaire-Short. Four zero-inflated negative binomial regression models were constructed to test the main and interactive effects of sex and anxiety sensitivity on PA outcomes.

Results: Females reported significantly fewer past-week PA minutes relative to males across all domains. At higher levels of anxiety sensitivity, males reported significantly fewer total PA minutes; whereas, total PA levels in females were not dependent on anxiety sensitivity level. Additionally, females with elevated anxiety sensitivity reported significantly more past-week walking minutes relative to females with low anxiety sensitivity, whereas the opposite pattern was observed in males.

Conclusion: This is the first study to our knowledge to examine sex-differences in anxiety sensitivity and PA, at varying PA intensities, among smokers. These data have the potential to inform sex-specific models of anxiety, PA, and smoking.

Keywords: ExercisePhysical activityAnxiety sensitivitysex differencesSmokers

Sociosexuality significantly predicted self-reported wellbeing during social lockdown for women, but not for men; those with high levels of desire for casual sex reported a greater negative impact on their self-reported levels of wellbeing

Changes in Sexual Desire and Behaviors among UK Young Adults During Social Lockdown Due to COVID-19. Liam Wignall et al. The Journal of Sex Research, Mar 29 2021.

Abtract: This study examined self-reported changes in young adults’ sexual desire and behaviors during the most significant social restrictions imposed to deal with COVID-19. Drawing on a survey of 565 British adults aged 18–32 collected at the peak of social lockdown restrictions, we document an overall decrease in sexual behaviors consistent with abiding by social restrictions. We found that the levels of sexual desire reported by women (but not men) decreased compared with reports of pre-lockdown levels. Participants in serious relationships reported more increases in sexual activity than people who were single or dating casually, and there were significant differences according to gender and sexual orientation. The perceived impact of subjective wellbeing of people with high sociosexuality scores was disproportionately associated with social lockdown but there was no effect for general health. Thus, the impact on sexuality and general wellbeing should be considered by policymakers when considering future social restrictions related to COVID-19 or other public health emergencies.


Social policy measures put in place to deal with COVID-19 have had profound social and economic consequences (e.g., Ali & Alharbi, 2020). The impact such measures have had on sexuality has received little attention, although initial exploratory studies document changes in desires and sexual behaviors (Lehmiller et al., 2020; Li et al., 2020; Stephenson et al., 2020). The current study drew on a survey of 565 young adults living in the UK (Mage = 25.35, SDage = 4.13) to examine changes in sexual desire and behaviors during social lockdown, with data collection occurring at the end of the period of the strictest social lockdown restrictions. Men reported higher sexual desire levels compared to women both before and during lockdown. Women showed a significant reduction in levels of sexual desire overall during lockdown; men showed a similar trend, but this did not reach statistical significance. Living arrangement (i.e., friends or others, partner, family or children, alone, other) had no detectable association with sexual desire levels either pre-lockdown or during lockdown and did not interact with gender.

Regarding sexual behaviors, men and LGB people reported significantly more increases in various sexual behaviors than women and heterosexual people, respectively, during social lockdown, in the context of a general decrease in reported sexual behaviors during the lockdown. Participants in relationships reported more increases in various sexual behaviors during social lockdown than those who were single or dating casually.

Lastly, general health and changes in subjective wellbeing were not predicted by sexual desire and sociosexuality scores for men or women, overall. However, sociosexuality significantly predicted self-reported wellbeing during social lockdown for women, but not for men. Further analysis showed that it was the desire aspect of sociosexuality which was associated with perceived impact on subjective wellbeing – those with high levels of desire for casual sex reported a greater negative impact on their self-reported levels of wellbeing than those with less desire for casual sex.

The gender differences found in some analyses (women reporting lower sexual desire levels than men both during and prior to lockdown and reporting a greater reduction in levels of sexual desire) are consistent with other COVID-19 research (Li et al., 2020). This could be due to increased levels of stress for women as a result of additional domestic labor (e.g., Collins et al., 2021) and may be associated with other symptoms emerging as a result of the pandemic and social restrictions. For example, increases in anxiety and depression have been recorded during the pandemic among both men and women and are associated with multiple factors, including the presence of children in the household due to school closings (Shevlin et al., 2020). Furthermore, depressive symptoms have been found to disproportionately affect young women (Vizard et al., 2020). Previous literature suggests that anxiety and depression can have an adverse effect on sexual desire (Beaber & Werner, 2009), although they can also increase sexual desire in some individuals (Bancroft et al., 2003; Lykins et al., 2006).

The changes in reported sexual behaviors during social lockdown are similar to the findings of other studies (e.g., Jacob et al., 2020; Stephenson et al., 2020), and have significant implications. There was a decreased occurrence of all sexual behaviors, although mixed results about change in frequencies of these sexual behaviors. This could be indicative of people following lockdown rules, particularly given that increases in masturbation were not associated with increases in sexual intercourse, potentially because some people who could not have sex turned to masturbation instead. Participants with unrestricted sociosexuality were more likely to report lower levels of general health and perceived impact on subjective wellbeing. This may come from the restrictions placed on casual sex to reduce transmission rates of COVID-19. Given people with higher levels of sociosexuality can also face prejudice from broader society (Vrangalova & Bukberg, 2015), it is important to consider interventions that target such people, perhaps through sexual health services. Similarly, LGB people with high levels of sexual desire during lockdown reported greater perceived impact on their wellbeing – replicating findings in the US (Sanchez et al., 2020), where one-third of gay and bisexual men reported negative coping behaviors such as binge drinking during lockdown (Stephenson et al., 2020).

Since the initial social lockdown on March 16th, 2020, across the UK, there have been several more variations of social lockdowns, with tier systems introduced throughout the UK. Further social lockdowns have occurred at different times in England, Scotland, Wales and Northern Island, and internationally. All these social restrictions lack advice on how to navigate sex, particularly for single people or couples LAT, thus privileging monogamous relationships. There was a de facto criminalization of sexual activity between consenting adults who did not live in the same household in the UK during lockdown, and legal restrictions on casual sex were effectively in place for much of 2020 in at least some parts of the UK because of the regional “tier” system introduced after the end of the first formal lockdown. Much greater recognition of the impact of lockdown restrictions on sexuality is needed, with consideration given to how social policy can minimize risk in sexual encounters without effectively banning them for extended periods of time: governments need to recognize the importance sex holds in the lives of individuals and society (Rubin, 2011).

In addition to the restrictions on sexual practice, there are other policy implications as they pertain to sexuality. Sexual and reproductive health services have been severely limited during social lockdown, with some closed altogether (Church et al., 2020; Nagendra et al., 2020), making access to treatment for STIs or fertility treatments more difficult. This may be particularly significant for people who continue to have sexual intercourse with others in contravention of social restrictions, including people who use sex as a coping mechanism against stress (Jaspal et al., 2021; Stephenson et al., 2020). This means that STIs may be currently under-reported and there will be significant public health implications as restrictions are eased. Likewise, public health bodies should plan for a potential significant increase in casual sex as restrictions ease and such behaviors no longer contravene lockdown guidance, given the drop in sexual behaviors found in this and other studies.

Limitations and Conclusion

While the findings provide important insights into sexual practices and behaviors of young adults in the UK during social lockdown due to COVID-19, this study was not without limitations. First, we employed a cross-sectional analysis, recruiting participants during the peak social lockdown restrictions. Second, we relied on retrospective self-report data for levels of sexual desire, which may provide inaccurate or biased results (Schmitt & Di Fabio, 2005). Longitudinal research is needed to explore what happens as social lockdown restrictions ease and whether reported changes persist, how quickly they fade and whether social or health interventions are needed in this endeavor. Relatedly, participants’ interpretations of questions may have been different (e.g., “before lockdown” could mean in the last month or year preceding lockdown). Future research should be more specific in questions. Third, the perceived impact on subjective wellbeing measure was developed for this study and not validated prior to the study, due to exceptional time restraints posed by the lifting of lockdown measures. As such, further research with established measures of wellbeing is needed. Relatedly, our measure for general health consisted of a single-item question; a more substantial measure of general health would strengthen reliability. Fourth, the sample was limited to predominantly White, heterosexual young adults. Further research needs to explore the experiences of sexual and ethnic minorities, as well as other age groups. Fifth, there may have been some selection bias: participants were recruited through an online participant recruitment pool, resulting in a convenience sample of people already willing to participate in research. These individuals may perceive more negative impacts of the pandemic, potentially having more free time due to furlough or needing extra income through survey participation. Finally, most of the significant effect sizes were quite small. To address these final limitations, future research should draw on nationally representative samples with larger sample sizes.

In conclusion, this study of UK young adults aged 18–32 found a general decrease in reported rates of sexual behaviors during social lockdown. For those who continued to engage in sexual activity, increases were predicted by gender and sexual orientation. Women reported lower levels of sexual desire compared to men, and also reported a significant decrease in sexual desire during lockdown. Women’s perceptions of the impact of lockdown on wellbeing were associated with attitudes to casual sex. Given these findings and the likelihood of future lockdown measures, in the UK and internationally, it is important to consider the impact of such measures on sexual desires and behaviors and how negative effects from them can be mitigated.

Saturday, April 3, 2021

Adult playfulness: An update on an understudied individual differences variable and its role in romantic life... including possible negative effects of playfulness

Adult playfulness: An update on an understudied individual differences variable and its role in romantic life. Kay Brauer  René T. Proyer  Garry Chick. Social and Personality Psychology Compass, March 16 2021.

Abstract: There is increasing interest in the study of individual differences in playfulness in adults; the way people frame or reframe situations in a way that they are experienced as personally interesting, and/or intellectually stimulating, and/or entertaining. In this review, we describe and discuss its role for romantic life. After a brief introduction, we will describe theoretical approaches as to why playfulness is important in romantic life (e.g., the signal theory of playfulness) and give an overview on empirical findings on assortative mating and its role in romantic relationships (e.g., for relationship satisfaction). Finally, we discuss future directions on playfulness in romantic life and singles and open research questions.

Check also Moraes YL, Varella MAC, Silva CSA, Valentova JV (2021). Adult playful individuals have more long- and short-term relationships. Evolutionary Human Sciences 3, e24, 1–10.


While the majority of findings suggests that playfulness contributes positively to relationships, no study has yet examined negative consequences of playfulness in relationships. Drawing on Berger et al.'s (2017) hypothesis that a maladaptive reframing process might contribute to develop psychiatric disorders that are related to cognitive biases (e.g., anxiety disorder); one might expect that some types of playfulness are associated with phenomena such as jealousy, the perceived threat of one's relationship (Pfeiffer & Wong, 1989). Taking the findings on relations with the mistrust facet into account (Proyer et al., 2019a), one might expect that whimsical playfulness accounts for actor effects in jealousy, whereas partners of those high in Lighthearted playfulness might show greater jealousy due to perceptions of lower commitment to the relationship and greater concern of the dissolution of the relationship. Furthermore, attachment styles describe how people approach and deal with close relationships (Fraley & Roisman, 2019) based on the two orthogonal dimensional anxiety (i.e., worries over close relationships) and avoidance (i.e., reducing interdependence by avoiding closeness). It would be desirable to examine potential consequences (e.g., mediator effects) of attachment on the associations between playfulness and relationship outcomes. One might argue that playfulness would go along with secure attachment (i.e., low anxiety and avoidance) as playful people have learned to adopt positive views on their relationships when learning their social skills, boundaries, and needs of others in childhood, as discussed with regard to the literature on children's playfulness (e.g., Burghardt, 2005; Lieberman, 1977; Youell, 2008).

Couple‐centered variables have not yet been examined. For example, dyadic coping describes how couples deal with stress by examining the interactions and coping strategies of each partner (Bodenmann, 2005). Prior studies have shown that playfulness relates to adaptive coping mechanisms, which permits dealing with stressors and stress positively (Chang et al., 2013; Magnuson & Barnett, 2013; Qian & Yarnal, 2011). Amongst others, those high in playfulness actively seek social support and companionship to reduce stress. However, no study has yet examined how couples deal with stressors from within (e.g., disagreement) and outside the relationship (e.g., child loss). While one might expect that playfulness would contribute to dyadic coping, this needs to be empirically tested since Herzberg (2013) has shown that individual and dyadic coping are not redundant (e.g., dyadic coping being the stronger predictor of RS and mediating the association between individual coping efforts and RS). Thus, it would be desirable to examine whether playfulness relates to dyadic coping similarly to findings from individuals and to study its effects for outcomes such as RS or disagreement.

Longitudinal studies could help clarifying relationships with criteria such as dissolution or having children and also address partners' co‐development of playfulness over time. The latter could clarify whether partners might become (1) more similar in their playfulness and (2) whether one's playfulness might spillover to the partner's playfulness. There is evidence that playfulness is malleable through minimal interventions (e.g., raising awareness of how one uses playfulness in everyday life; Proyer et al., 2020; Proyer et al., 2021) and it is feasible that one could be stimulated by their partner to be more playful—or, at least, do more playful things and behave more playful. Moreover, effects of co‐development on outcomes such as the quality and quantity of conflicts and RS would be of interest (e.g., Allemand & Martin, 2016).

Prior research has relied mainly on self‐reports of playfulness. An extension to partner/peer reports of playfulness and instruments that allow a good description of playful behaviors in couples is desirable. For the latter, the PLC (Proyer et al., 2018b) might be a good starting point, pending revision of the initial list of items. Also, observational designs could help to learn more about how playfulness is expressed and used in couples. For example, how partners use their playfulness to solve practical problems and behave in situations that potentially go along with conflict could be examined.

Adult playful individuals have more long- and short-term relationships

Moraes YL, Varella MAC, Silva CSA, Valentova JV (2021). Adult playful individuals have more long- and short-term relationships. Evolutionary Human Sciences 3, e24, 1–10.

Abstract: Number of romantic/sexual relationships is suggested as a proxy of potential reproductive success. Cross-culturally, both sexes desire playful long-term mates and playfulness predicts relationship quality. It is yet to be tested, however, if playfulness is associated with number of long- and short-term relationships. We hypothesised that specific playfulness dimensions would correlate with the number of lifetime short- and long-term relationships. We expected that lighthearted playfulness would be associated with more short-term relationships, while other-directed playfulness would be associated with the number of long-term relationships. In total, 1191 Brazilian adults (mean age = 28.7 years, standard deviation = 10.2) responded to online sociodemographic questions and a playfulness inventory. Other-directed playfulness positively predicted the number of short-term and long-term partners in men and whimsical playfulness predicted the number of short-term relationships in women. This suggests that playfulness is used by both sexes to compete for access to more and better mates, but in slightly different ways. For the first time, we show that playful adults have more partners and that playfulness can be used as a part of mating strategies.

Keywords: Short- and long-term relationships; adult playfulness; mate selection; sex differences

Although the men indicated a willingness to pursue slightly older partners in surveys, they rarely acted on these statements in real-life dating

Partner preference and age: User's mating behavior in online dating. Marketa Setinova, Renáta Topinková. Journal of Family Research, Mar 29 2021.


Objective: We test whether real online-user mating behavior corresponds with expectations from both the sociobiological and social perspectives and explore the age differentials that individuals opt for when searching for a mate and how this evolves relative to the user’s age and gender.

Background: Age plays a vital role in partner choice. Previous studies have focused primarily on age differences between couples and their self-reported preferences for partners of a certain age. However, little is known about how age affects behavior in the online dating market.

Method: We use behavioral data from a Czech online dating app, Pinkilin and analyze 197,519 invitations that users sent to each other in July 2017.

Results: Men strongly prefer young women, and women prefer partners of their age or slightly older. At older ages, men’s preference for younger women widens, while women's preferences become more diverse. Homogamous tendencies are stronger among younger users and women.

Conclusion: Overall, our results corroborate those of previous research on online dating, but we extend this research in terms of age differences in the Czech context.

Keywords: online dating, age homogamy, partner preference, Czechia


In surveys, men state an acceptable partner age interval of 10 years younger and five years older. As they age, their willingness to pursue younger women increases, but their non-acceptance of older women remains constant (Conway et al. 2015; Schwarz & Hassebrauck 2012). Data from online dating confirm men’s strong preference for young women and their avoidance in terms of contacting older partners (Fiore & Donath 2005; Rudder 2014; Skopek et al. 2011). Our research is in line with the previous evidence. Young men showed a preference for women their age. However, this preference declined with age, and they gradually shifted to younger partners. With age, they grew more ambitious and were willing to cross larger age gaps toward younger partners. Overall, the men in our data set avoided older women, including women who were only slightly their senior. This avoidance was stable for all ages, thereby confirming that although the men indicated a willingness to pursue slightly older partners in surveys, they rarely acted on these statements in real-life dating. This highlights the importance of mixing digital trace data with traditional surveys, as stated preferences may not necessarily translate to future actions (Schmitz et al. 2009).

As for women, their stated partner age interval was eight years older and five years younger. With age, they grew accepting of younger partners and became less willing to contact older men (Conway et al. 2015; Schwarz & Hassebrauck 2012). Looking at the online dating market, women showed a tendency to mate with partners of their age and slightly older. Women under 30 were not open to contact from younger men, but as they aged, their openness toward younger partners increased (Rudder 2014; Skopek et al. 2011). Again, this was largely supported in our Czech data set. The youngest women had a preference for older partners over partners their age. However, up to 30 years old, they preferred partners of the same age or up to nine years their senior. As women aged, they were more open to younger men and more restrictive toward older men. The older the woman was, the more willing she was to cross larger age gaps toward younger partners. As mentioned earlier, the same trend could be observed for men. However, there was a lag as to when this shift toward younger partners occurred. Women started initiating contact with significantly younger men (5–9 years younger) later, in their mid-forties, while men developed this preference around their mid-thirties.

The support for evolutionary theory in our analysis is, therefore, fairly strong. Two interesting findings are noteworthy. First, in comparison to previous research, men were, from an early age, very hesitant to contact older women. This can be seen as an impact of strong local gender norms that, at least in men’s eyes, may highlight the importance of reproduction in dating and support the paradigm that the husband should be older than his wife. Men’s tendency to avoid older women in the early stages of dating could also be one of the mechanisms behind the higher incidence of male age hypogamy in Czechia (Katrňák 2008). Second, we observed older women around their mid-forties contacting significantly younger men. This tendency was visible in past online dating research (Rudder 2014; Skopek et al. 2011) but did not fully correspond with expectations from evolutionary theory. Perhaps older women are aware of the marriage squeeze and believe they have more chances with a younger partner who might be attracted to their experience and status. Alternatively, they may be more economically independent than younger women and may not be drawn to older partners because they already have their own resources (Rudder 2014, confirms that response rates to older women’s messages from younger males are fairly high). Growing levels of female hypogamy by older women in Czechia might support this hypothesis (Katrňák 2008). Another interpretation could be related to seeking a sexual partner rather than one for reproduction. Not all dating site users are in search of a serious relationship, and older women seeking younger males for sexual pleasure, called “cougars” in popular culture, can offer noncommitted sex and demand no financial provision or status from men in return (Lowen 2019). Furthermore, in the post-reproductive phase, women may not place such importance on status, even when seeking a serious relationship. Without further data, however, it is difficult to understand the reason behind these two inconsistencies.

We expected people to feel less culpable about the outcome if they acted in accordance with their superior’s injunction than if they made the decision themselves, but they felt more culpable when they followed orders

Feelings of Culpability: Just Following Orders Versus Making the Decision Oneself. Maayan S. Malter, Sonia S. Kim, Janet Metcalfe. Psychological Science, April 2, 2021.

Abstract: In five experiments (N = 1,490), participants were asked to imagine themselves as programmers of self-driving cars who had to decide how to program the car to respond in a potential accident: spare the driver or spare pedestrians. Alternatively, participants imagined that they were a mayor grappling with difficult moral dilemmas concerning COVID-19. Either they, themselves, had to decide how to program the car or which COVID-19 policy to implement (high-agency condition) or they were told by their superior how to act (low-agency condition). After learning that a tragic outcome occurred because of their action, participants reported their felt culpability. Although we expected people to feel less culpable about the outcome if they acted in accordance with their superior’s injunction than if they made the decision themselves, participants actually felt more culpable when they followed their superior’s order. Some possible reasons for this counterintuitive finding are discussed.

Keywords: decision making, judgment, morality, autonomous vehicles, perspective taking, COVID-19, trolley problem, agency, Nuremberg defense, open data, open materials

Women find men less attractive as new long-term partners if they have first imagined them as one-night stands; men find women less attractive as one-night stands if they have first imagined them as new long-term partners

Short term, long term: An unexpected confound in human-mating research. Paola Bressan. Evolution and Human Behavior, April 2 2021.

Abstract: Here I report that, when partnered people judge the facial attractiveness of potential mates for a short- and a long-term relationship, the order in which the two conditions are presented biases responses in a systematic manner. Women and men display symmetrical biases. Women find men less attractive as new long-term partners if they have first imagined them as one-night stands. Men find women less attractive as one-night stands if they have first imagined them as new long-term partners. On a total sample of over 3000 individuals from different studies, I show that both biases are robust and replicable in partnered people and neither is found in singles. Alas, so far no study has statistically controlled the effect of the order in which participants consider the two types of relationships. Whatever their interpretation, these biases are capable of producing spurious or inconsistent associations and mislead us when we compare studies that on the surface appear similar—most notably, direct and conceptual replications.

Keywords: Facial attractivenessMate choiceShort-term relationshipsLong-term relationshipsPartnership statusOrder effectsSex differences

Friday, April 2, 2021

Great apes, like humans, possess impressive knowledge of their social world: they remember social partners for decades, encode their dispositions and relationships, & even track their perspectives in surprisingly rich ways

Origins of the social mind: Cognition in humans and other apes. Christopher Krupenye. European Human Behaviour and Evolution Association, 15th Conference, Mar 2021.

Abstract: Few traits characterise humans more profoundly than the complexity of our social lives, and the depth of our insights into the social and mental lives of others. To predict behaviour and make decisions in a dynamic and uncertain social world, we track others’ social relationships, evaluate others based on their behaviour or identity, and even attempt to infer their thoughts and emotions. That our potential social partners possess these skills, too, is precisely what makes the social world so complex. In turn, we must manage our reputation and relationships, adhere to the norms of our group, and strategically navigate manifold cooperative and competitive interactions. Cognition is at the heart of what makes social life so demanding and thus, to characterize the origins of human social complexity, we must understand the origins of our social cognition. I will present a series of comparative experiments with humans and our closest phylogenetic relatives, chimpanzees (Pan troglodytes) and bonobos (Pan paniscus), aimed at identifying shared traits that were likely present 6-9 million years ago in our last common ancestor, as well as spotlighting unique features of the human mind. This work demonstrates that great apes, like humans, possess impressive knowledge of their social world: they remember social partners for decades, encode their dispositions and relationships, and even track their perspectives in surprisingly rich ways. Together, this body of research suggests  that the roots of our social minds are discernible in the minds of our closest relatives, and extend deep into our evolutionary history.

Happy people retain their jobs because they enjoy doing their work; happiness leads people to place more weight on enjoyment than on competence in the enjoyment-competence trade-off context

Enjoyment Versus Competence Trade-Off: Happy People Value Enjoyment Over Competence More Than Unhappy People. Mina Jyung, Incheol Choi & Yerin Shim. Journal of Happiness Studies, Apr 2 2021.

Rolf Degen's take: When compared with unhappy individuals, happy people value work they enjoy more than work that they perform well

Abstract: Do people prefer a job that promotes feelings of enjoyment, or of competence? The present research examined the role of individuals’ happiness in choosing the type of work to engage in when selecting between two characteristics of the work—enjoyment and perceived competence. Studies 1, 2, and 3 revealed that happier people are more likely to value (Study 1) and to choose (Studies 2 and 3) work they enjoy over work in which they expect high competence. In Study 3, a direct manipulation of happiness increased preference for enjoyment, but not for competence. Finally, Study 4 found that happy people, when compared with their unhappy counterparts, retain their jobs because they enjoy doing their work. Together, the findings suggest that happiness leads people to place more weight on enjoyment than on competence in the enjoyment-competence trade-off context.

Thursday, April 1, 2021

Cues associated with food trigger release of homeostasis regulating hormones, which regulate hunger, prevent hypoglycemia, & improve metabolism; those anticipatory hormonal responses are largely learned phenomena

Food anticipatory hormonal responses: a systematic review of animal and human studies. Aleksandrina Skvortsova et al. Neuroscience & Biobehavioral Reviews, April 1 2021.


• Cues associated with food trigger release of homeostasis regulating hormones.

• Food anticipatory hormonal responses are consistently found in animals and humans.

• These responses regulate hunger, prevent hypoglycemia, and improve metabolism.

• Food anticipatory hormonal responses are largely learned phenomena.

• Food anticipatory hormonal activity is impaired in eating and metabolic disorders.

Abstract: Food anticipatory hormonal responses (cephalic responses) are proactive physiological processes, that allow animals to prepare for food ingestion by modulating their hormonal levels in response to food cues. This process is important for digesting food, metabolizing nutrients and maintaining glucose levels within homeostasis. In this systematic review, we summarize the evidence from animal and human research on cephalic responses. Thirty-six animal and fifty-three human studies were included. The majority (88%) of studies demonstrated that hormonal levels are changed in response to cues previously associated with food intake, such as feeding time, smell, and sight of food. Most evidence comes from studies on insulin, ghrelin, pancreatic polypeptide, glucagon, and c-peptide. Moreover, impaired cephalic responses were found in disorders related to metabolism and food intake such as diabetes, pancreatic insufficiency, obesity, and eating disorders, which opens discussions about the etiological mechanisms of these disorders as well as on potential therapeutic opportunities.

Keywords: anticipatory hormone releasecephalic responsesfood

4. Discussion

There is a large body of research demonstrating that cephalized organisms (ranging from insects to mammals) anticipate food intake via environmental cues with the aim to maintain homeostasis by adjusting their hormonal levels. Anticipatory hormonal changes, so-called cephalic responses, were found in a wide range of hormones but most evidence exists for insulin, ghrelin, pancreatic polypeptide, glucagon, and c-peptide. Animal research is very consistent in finding anticipatory hormonal changes with almost all studies demonstrating significant results, while the majority of human research also finds anticipatory hormonal changes. There is also some evidence for impaired cephalic responses in several metabolic and eating disorders in comparison to healthy participants, although more research is needed. Taken together, the current systematic review shows that the release of a wide range of hormones happens prior to food consumption both in animals and humans and it plays an important role in preparing the organisms for the food ingestion.

The direction of the hormonal changes in response to food anticipation mirrors the hormonal changes in response to food digestion: insulin, ghrelin, glucagon, pancreatic polypeptide, gastrin, and c-peptide levels increase. These processes indicate early adaptive preparation of the organism to the food digestion. The only hormone that does not have a direct relation to metabolism, but was repeatedly investigated in the context of food anticipation, is cortisol (corticosterone in rodents). Cortisol and corticosterone increase were found during food anticipation (Ott et al., 2012) (Coover et al., 1984Moberg et al., 1975). Moreover, levels of cortisol and corticosterone dropped rapidly after food consumption (Moberg et al., 1975). Speculatively, food anticipation triggers a stress response in the organism and, therefore, leads to cortisol release. Possibly, an increase in stress hormones is necessary to increase alertness in animals in anticipation of food (Feillet, 2010).

It is still not entirely known to what extend cephalic responses are triggered by classical conditioning and whether some of them can be inborn. The only study included in this review that investigated this question directly, (Bernstein and Woods, 1980) demonstrated that cephalic insulin release in response to sweet taste is absent in newborn rat pups but already present in 21-22 day-old rats. Also, multiple experiments in both animals and humans showed that cephalic responses are present in subjects who followed fixed eating pattern in contrast to subjects who were fed ad libitum or without a fixed pattern (Holmes et al., 1989Moberg et al., 1975Woods et al., 1977). Therefore, evidence points that cephalic responses are to a large extent dependent on classical conditioning. That is, organisms learn that certain stimuli predict the availability of the food, and respond to these stimuli with cephalic hormones release to prepare the body for food consumption. Cephalic responses have been shown to be elicited not only by the cues that naturalistically predict food (such as time of eating/feeding or smell of food) but also by conditioning to neutral stimuli such as the sound of a door opening (Strubbe, 1992), or a mixed stimulus of a sound and a light (Storlien, 1985).

In addition to memory processes, such innate component, as circadian modulation, seems to affect food anticipatory hormonal responses. One study included in this review investigated a role of circadian clock in the cephalic responses (Patton et al., 2014). Patton and colleagues (2014) demonstrated food anticipatory corticosterone and ghrelin release to be more pronounced in the mice that were fed during the dark phase, than in the mice fed during the light phase. Mice are nocturnal animals, and free fed mice tend to exhibit food anticipatory activity during night. Therefore, the food anticipatory activity seems to be enhanced in the cases when feeding schedule corresponds to the light-dark rhythms. In case when there is a mismatch between dark-light cycle and the feeding pattern, for example, if food is given only in the usual sleep phase, the food anticipatory hormonal responses still appear (Feillet, 2010Mistlberger, 1994) but might be of a smaller magnitude than in cases when there is no such a mismatch (Patton et al., 2014).

Another not well understood question about the cephalic responses, is what stimuli trigger it and in what cases. There is a discrepancy between animal and human research regarding the question whether mere taste elicits anticipatory hormone release or consumption of whole organoleptic stimulation of foods is needed. A large number of human studies failed to find anticipatory insulin release in response to a sweet taste of a nun-nutritive or low caloric substance alone (Abdallah et al., 1997Bruce et al., 1987Cedernaes et al., 2016Härtel et al., 1993Morricone et al., 2000Smeets et al., 2005Teff et al., 1995). At the same time, the response was found in the large number of studies that used sham feeding with whole foods (Buysschaert et al., 1985Glasbrenner et al., 1995Goldschmiedt et al., 1990Teff et al., 199519931991). Moreover, a number of studies found that there are responders and non-responders to the taste stimulation (Bellisle et al., 1985Dhillon et al., 2017Teff et al., 1991). This might indicate that a combination of tactile, olfactory and taste stimulation provided by whole foods is needed to elicit a reliable cephalic response in humans. At the same time, it seems not to be the case in animals. All animal studies included into this review found cephalic hormone release to the sweet taste alone. Various reasons can explain this discrepancy between animal and human research. For example, cognitive factors play an important role in food anticipation in humans. Also, most people have previous experience with tasting various sweeteners that might affect their cephalic responses, while laboratory animals usually follow standard diets and are naïve to low caloric sweeteners.

Underlying neural mechanisms of the cephalic hormonal responses were investigated only in a few animal and human studies. It is proposed that in response to the food cues, the brain initiates insulin secretion by directing the signal through the vagus nerve to the pancreas (Woods, 1991). Animal research demonstrated that vagotomy, a surgical removal of a part of vagus nerve, leads to the disappearance of cephalic responses (Bernstein and Woods, 1980Herath et al., 1999Storlien, 1985). Human research confirms these results: administration of atropine, a drug that opposes the actions of the vagus nerve by blocking the acetylcholine receptors, was shown to abolish cephalic insulin (Sjöström et al., 1980) and pancreatic polypeptide release (Veedfald et al., 2016). Another substrate that has been proposed to underlie cephalic responses is the ventromedial nucleus of the hypothalamus, a brain area that is linked to satiety (Kurrasch et al., 2007). Animals with lesions of this area exhibit no cephalic responses to sweet taste and a complex stimulus previously associated with food (Berthoud et al., 1980a,bStorlien, 1985). Another human study demonstrated that the upper hypothalamus might play a role in cephalic hormone release but only when stimulated by both sweet taste and high energy content: they showed that the injection of glucose, and not aspartame (sweet non-caloric taste) or maltodextrin (non-sweet carbohydrate) leads to significant decreases in the activity in the upper hypothalamus (Smeets et al., 2005).

Interestingly, human research shows an important role of cognition in food anticipatory hormonal releases. For example, a mere discussion about food triggered insulin release (Feldman and Richardson, 1986) and expected food palatability influenced cephalic responses (Rigamonti et al., 2015). Moreover, Crum and colleagues (Crum et al., 2011) demonstrated that the decrease of ghrelin levels after food consumption was larger in magnitude in participants who thought that they had consumed a high caloric shake in comparison to the participants who thought that the shake was low caloric (in reality it was the same shake). Cognition might also explain the discrepancy in the results between the studies that measured cephalic responses in humans to food consumption and sham feeding. While animal research found that both of these methods are very successful in eliciting anticipatory hormone release, a number of human studies that involved sham feeding, found no such responses. Participants in the studies with sham feeding knew that they would have to discharge the consumed food, and possibly, this knowledge might have affected their anticipatory hormonal responses. These studies point to the importance of conscious expectations in this physiological process: mere thoughts about food that people have might affect their hormonal responses. Additionally, the role of cognitive capacities in food anticipatory responses have never been studied before. For instance, no research in this topic have been done in infants or in people with cognitive disabilities. Future research should look at how cognition about food and cognitive capacities influence learned food anticipatory responses.

Studies that investigated cephalic responses in clinical populations demonstrate that anticipatory hormonal responses were affected in patients with diabetes with cardiac autonomic neuropathy (Buysschaert et al., 1985Glasbrenner et al., 1995), obesity (Brede et al., 2017Johnson and Wildman, 1983Osuna et al., 1986Sjöström et al., 1980), eating disorders (Broberg and Bernstein, 1989Monteleone et al., 20102008Moyer et al., 1993), pancreatic insufficiency (Wøjdemann et al., 2000), and kidney and pancreas transplantation (Secchi et al., 1995). However, the number of studies that included clinical populations is limited. It remains unknown whether disturbed cephalic responses play a causal role in the development of some of these disorders, or, alternatively, are consequences of them. Future studies should investigate the role of cephalic responses in the development of metabolic disorders and the possibility of using cephalic responses as a diagnostic tool for some of these disorders.

Several limitations of the studies included into the current review should be mentioned. First of all, the risk of bias assessment demonstrated that the majority of the studies included in this review did not report enough information to make it possible to objectively assess the bias. Particularly it applies to the animal research that did not provide information regarding the method of assigning animals to different conditions and blinding of the personnel. Similar problems, but to a lesser extent, are present in human studies. Only one study preregistration was available in open access and the majority of the studies did not report whether the analysis of outcome was done by blinded personnel. Moreover, none of the studies described whether the statistical power calculation had been done prior to the study what makes it difficult to interpret null findings. Furthermore, we found that while almost all animal studies found cephalic responses, human research varied more with respect to the results. This phenomenon can be explained by several reasons. Firstly, a larger publication bias might exist in animal research. It has been recently demonstrated that animal studies with null-findings are often not published creating a large bias in the animal literature (ter Riet et al., 2012). Secondly, additional factors might play a role in humans that are presumably less important in animals, for example, cognition. Most of the human studies, however, did not take into considerations such factors, such as expectation of participants, even though cognitive factors have been shown to affect cephalic responses (Crum et al., 2011Feldman and Richardson, 1986). Ignoring these potential confounding factors, might have led to the occasional null findings in human studies. Most of the animal and human research has been done either in males or in mixed-sex samples. Only one study included in this review looked at sex differences: they demonstrated that anticipatory ghrelin release peaks at different times in male and female mice and also in orchidectomized mice. Sex differences have been also found in glucose and lipid metabolism (Gur et al., 1995), which may potentially also affect anticipatory hormonal responses. Therefore, it is essential that future research focus on potential sex differences in the food anticipatory hormone release. Furthermore, many different methods and protocols were used for measuring anticipatory hormonal responses, and almost no study compared different methods. These differences complicate interpreting null-findings of some of the studies. For example, several studies that involved sham feedings found no cephalic insulin release (Crystal and Teff, 2006Teff et al., 1995), however, as every study used a different procedure of sham feeding (different foods, various times of chewing, various moments of sample collections), it remains unknown whether these null findings can be explained by the protocol used or whether cephalic insulin release does not occur in all cases.

Better understanding of cephalic hormonal responses brings several clinical possibilities. First, consumption of artificial low-caloric or non-nutritional sweeteners increases in modern society as these sweeteners are often added to common beverages and foods. It is still poorly understood how such discrepancy between the sweet taste and a low nutritional content can affect cephalic responses and whether it plays a role in the development of obesity and metabolic disorders. Moreover, the evidence from the current review indicates that cephalic responses might be affected in patients with metabolic disorders, however, the number of studies on this topic is limited. For example, it is unknown how impairment of cephalic responses progresses from obesity to metabolic syndrome and diabetes type 2. Possibly, measuring cephalic responses might be used as a predictive tool for the development of metabolic disorders.

The present review confirmed that there is a large body of literature supporting the existence of food anticipatory hormonal release. Moreover, there is some preliminary evidence at impairment of anticipatory hormonal responses in a range of disorders related to metabolism and food intake. More research is needed to understand the role of such impairments in cephalic responses and possibility to use cephalic responses as a predictor for the development of metabolic disorders.