Thursday, April 15, 2021

Opening up relationships: Those with perceptions of higher‐quality alternatives had clearly more interest in consensual non‐monogamy

Quality of alternatives positively associated with interest in opening up a relationship. Geoff MacDonald  Yoobin Park  Alathea Hayes  Isabelle Vanasse Grosdidier  Sun W. Park. Personal Relationships, April 14 2021.

Abstract: We use the Investment Model framework to examine what relationship features are associated with interest in and positive evaluations of consensual non‐monogamy (CNM) among individuals in monogamous relationships. In data sets from the United States (Study 1), Europe (Study 2), and Korea (Study 3; total N = 886), perceptions of higher‐quality alternatives were consistently associated with more interest in CNM. Further, consistent with previous work on commitment‐motivated relationship maintenance processes, we found support for an indirect effect whereby lower commitment was associated with higher perceived attractiveness of alternatives, which in turn was associated with more interest in CNM. The data suggest that the idea of CNM is likely to be most attractive to those who see themselves as having higher‐quality relationship options.

How Narcissism Shapes Responses to Antisocial and Prosocial Behavior: Hypo-Responsiveness

How Narcissism Shapes Responses to Antisocial and Prosocial Behavior: Hypo-Responsiveness or Hyper-Responsiveness? Jiafang Chen et al. Personality and Social Psychology Bulletin, April 15, 2021.

Abstract: Narcissists have a relatively higher proclivity for displaying antisocial rather than prosocial behaviors, suggesting a comparatively higher tendency for unfavorably impacting societies. However, maintenance of social order also depends on appropriate responses to others’ social behavior. Once we focus on narcissists as observers rather than actors, their impact on social functioning becomes less clear-cut. Theoretical arguments suggest that narcissists could be either hypo-responsive or hyper-responsive to others’ social behavior. Across four studies, we examined narcissists’ responsiveness to variations in others’ antisocial and prosocial behaviors. Results showed that narcissists differentiated less between others’ antisociality/prosociality, as reflected in their subsequent moral character evaluations (Studies 1–4) and reward and punishment (Studies 3 and 4). These results suggest that narcissists are hypo-responsive to others’ social behaviors. Implications and directions for future research are discussed.

Keywords: narcissism, social perception, responsiveness, moral character evaluation, reward/punishment

General Discussion

We examined how observers’ narcissism shapes their responsiveness to others’ social behavior. Across four studies, narcissists were consistently less responsive to variations in actors’ antisocial or prosocial behavior, providing evidence for a hypo-responsiveness rather than a hyper-responsiveness hypothesis. Specifically, narcissists differentiated less between others’ antisocial versus control behavior (Study 1), others’ prosocial versus control behavior (Study 2), and others’ antisocial versus prosocial tendencies (Studies 3 and 4), which was reflected in their subsequent moral character evaluations (Studies 1–4), and reward and punishment behavior (Studies 3 and 4).

Theoretical and Practical Implications

The present research has several theoretical implications. First, it extends prior research on narcissists’ responses to others’ behavior by switching from the perspective of a direct target or victim of (close) others’ behavior (Back et al., 2013Bushman & Baumeister, 1998) to an indirect target or third-party observer perspective, examining responses to both antisocial and prosocial behaviors, and identifying downstream consequences of narcissists’ hyposensitivity mainly for moral character evaluations and also indirectly for reward and punishment. Therefore, our findings improve our understanding of narcissists’ dynamic self-regulatory processing in interpersonal situations (Morf & Rhodewalt, 2001) from more inclusive perspective.

Previous work has shown that, to maintain a positive self-concept in the agentic (vs. communal) domain (e.g., power, status; Grijalva & Zhang, 2016), narcissists are hyper-sensitive and vigilant to external cues related to status or power (Grapsas et al., 2020). Our findings on the mediation effects of recognized antisociality/prosociality complement this work by illuminating narcissists’ lower sensitivity to or recognition of communal information. Moreover, our exploratory results showing narcissists’ differentiation in perceived similarity to a successful/unsuccessful target (agentic information) provided further evidence for narcissists’ higher sensitivity to agentic than communal information (see detailed results in Supplemental Materials). Thus, it does not appear that narcissists are indiscriminately less sensitive to all contexts.

Alternatively, narcissists’ hypo-responsiveness could stem from their awareness of others’ underlying motivations for antisocial and prosocial behaviors. Both antisocial and prosocial behaviors can constitute a route to positive self-presentation (Flynn et al., 2006Van Kleef et al., 2011), with antisocial behaviors being more commonly adopted by narcissists to gain status or attention (Adams et al., 2014). Although narcissism is unrelated to self-enhancement through prosocial behaviors (Nehrlich et al., 2019), narcissists sometimes present prosocial behaviors for selfish reasons, like gaining career experience (Brunell et al., 2014), or for praise and attention (Konrath et al., 2016). Thus, it is possible that narcissists are less responsive to others’ prosocial behaviors because they are aware of others’ potentially selfish motivations, and show greater tolerance for others’ antisocial behaviors which they themselves use to gain attention or status. Our exploratory results (see Supplemental Materials) showed that narcissists’ hypo-responsiveness on moral character evaluation was related to their lower self-reported antisociality/prosociality. One might posit that narcissists’ hypo-responsiveness resulted from them perceiving relatively lower (higher) similarity with the prosocial (antisocial) target. However, we found that narcissists showed no difference in perceived similarity with the two targets, which could be another manifestation of their insensitivity. Nonetheless, further examining the role of similarity in the scope of narcissists’ responses to others is a fruitful avenue for future research.

Interestingly, self-relevance was not found to play a role in affecting narcissists’ responsiveness in Study 1, with narcissists’ hypo-responsiveness being observed across both high and low self-relevance conditions. The fact that the antisocial actor pushed in at the front of the queue rather than immediately in front of participants might have rendered this behavior less psychologically proximate and less salient despite being relatively self-relevant, removing it from narcissists’ radar and reducing the need to allocate cognitive resources to encode this behavior (Wise et al., 2009). Consequently, such behavior may not have been perceived as a personal affront by narcissists (Lustman et al., 2010), reducing its perceived threat to their self-concept. Thus, this finding suggests that narcissists ignore threatening information that is not explicitly directed at them. Given that Back et al. (2013) did report that narcissists show revenge-related reactions when directly harmed by close others (i.e., friends), future research could examine the degree to which the anti- or prosocial behavior is directly aimed toward the narcissist while also considering the specific relationship between the narcissist and the protagonist.

Our findings that narcissists punished more overall regardless of their co-participant’s behavioral tendencies also contribute to research on narcissists’ unprovoked aggression (Park & Colvin, 2015Reidy et al., 2010). Narcissists’ greater punishment of others might reflect their desire to assert their dominance vis-à-vis the other participant.

In terms of practical implications, our findings indicate that narcissists respond less discriminately on rewarding and punishing antisocial versus prosocial behaviors, which may over time lead to an increase in antisocial behaviors and a decrease in prosocial behaviors (Fehr & Fischbacher, 2004Henrich et al., 2005). Such potential adverse influences may be particularly disconcerting when narcissists occupy influential positions. Recent research showed that narcissistic leaders sanctioned integrity-norm violators less and were associated with organizational cultures that devalued integrity (O’Reilly et al., 2018). Considering that narcissists have a higher chance of rising to powerful positions (Nevicka et al., 2011), organizations should introduce clear principles of conduct combined with incentives and penalties that are independent of leaders’ decisions to reduce the potentially detrimental impact of such leaders on organizations’ moral climate.

Strengths, Limitations, and Suggestions for Future Research

Our research has several strengths. We used different antisocial and prosocial behaviors and tendencies to demonstrate the generalizability of narcissists’ hypo-responsiveness to others’ social behavior and consistently found narcissists’ hypo-responsiveness in moral character evaluation. Furthermore, our findings show a similar effect for reward and punishment in Study 3, further lending some support for narcissists’ hypo-responsiveness. Finally, we illuminated underlying mechanisms by establishing recognition of others’ antisociality/prosociality as a mediator of narcissists’ moral character evaluations, reward, and punishment.

This research also has some limitations. Despite the validity and wide usage of the VDT (DeWall et al., 2013Øverup et al., 2017), participants’ engagement in punishing may be affected by not seeing the consequences of their punishment behavior. Therefore, it would be helpful to enhance participants’ engagement in behavioral responses by adopting more direct punishment measures, such as noise blasts (Bushman & Baumeister, 1998). Moreover, because this was a one-shot study and there was little reason for participants to believe that the responses would affect their co-participant’s future behaviors, participants’ behavior toward their co-participant was unlikely to involve their conscious desire to regulate the co-participant’s future behavior. Future research could examine situations where punishment and reward behavior can be seen to have more observable impact on others over time.

While our research focused on im(morality) in the communal domain, future research could examine how narcissists, as third-party observers, respond to others’ (in)justices in the agentic domain that could harm or benefit someone else’s striving for status or power. For example, how would narcissists respond to seeing someone cheating in an examination, or seeing someone giving a classmate a leg up? Because narcissists’ higher feelings of power may allow them to better distinguish goal-relevant versus goal-irrelevant information (Guinote, 2007), they may categorize status- or power-related information as irrelevant if such information does not affect their own status or power. Therefore, they may be less responsive to such irrelevant information in spite of its status or power component. Thus, narcissists as a third party may likewise demonstrate hypo-responsiveness to others’ (in)justices in the agentic domain. 

The tendency toward last-minute cancellations (“social zapping”) is mainly predicted by Machiavellianism & narcissism; attentional impulsivity & timeliness procrastination are additional predictors

Predictors of social-zapping behavior: Dark Triad, impulsivity, and procrastination facets contribute to the tendency toward last-minute cancellations. Silke M. Müller, Dario Stolze, Matthias Brand. Personality and Individual Differences, Volume 168, 1 January 2021, 110334.


• Investigation of the tendency toward last-minute cancellations (“social zapping”).

• Dark Triad, maximizing, procrastination, and social zapping correlate positively.

• Social zapping is mainly predicted by Machiavellianism and narcissism.

• Attentional impulsivity and timeliness procrastination are additional predictors.

• Social zappers tend to self-serving, short-sighted decisions at the expense of others.

Abstract: The tendency to cancel appointments at short notice in favor of supposedly better alternatives is referred to as “social zapping”. Social zapping is positively associated with maximizing tendencies and problematic social networks use. However, empirical investigations on which additional personality characteristics predict social-zapping behavior are yet missing. In this study, a sample of N = 190 adults performed a questionnaire-based survey assessing different personality facets and social zapping tendency. Measures included the Dark Triad - Dirty Dozen scale, Barratt Impulsiveness Scale, Maximization scale, Pure Procrastination Scale, Fear of Missing Out (FoMO) scale, and the Social Zapping Scale. On a bivariate level, social zapping correlated positively with all other measures except for trait FoMO. The results of the multiple regression analysis showed that social zapping was mainly predicted by two dimensions of the Dark Triad, i.e. Machiavellianism and narcissism, as well as attentional impulsivity and the timeliness dimension of procrastination. Based on the results, social zappers can be characterized as individuals who tend to make self-serving and/or impulsive short-sighted decisions at the expense of others. Social zapping is a phenomenon of inherent self-interest, where individuals cancel appointments spontaneously (at the last minute) with others to pursue options they deem best for themselves.

Keywords:  Social zappingDark TriadFear of Missing OutMachiavellianismNarcissismPsychopathyMaximizationProcrastination

Professionals keep overestimating replicability of research

Gordon M, Viganola D, Dreber A, Johannesson M, Pfeiffer T (2021) Predicting replicability—Analysis of survey and prediction market data from large-scale forecasting projects. PLoS ONE 16(4): e0248780, Ap4 14 2021.

Abstract: The reproducibility of published research has become an important topic in science policy. A number of large-scale replication projects have been conducted to gauge the overall reproducibility in specific academic fields. Here, we present an analysis of data from four studies which sought to forecast the outcomes of replication projects in the social and behavioural sciences, using human experts who participated in prediction markets and answered surveys. Because the number of findings replicated and predicted in each individual study was small, pooling the data offers an opportunity to evaluate hypotheses regarding the performance of prediction markets and surveys at a higher power. In total, peer beliefs were elicited for the replication outcomes of 103 published findings. We find there is information within the scientific community about the replicability of scientific findings, and that both surveys and prediction markets can be used to elicit and aggregate this information. Our results show prediction markets can determine the outcomes of direct replications with 73% accuracy (n = 103). Both the prediction market prices, and the average survey responses are correlated with outcomes (0.581 and 0.564 respectively, both p < .001). We also found a significant relationship between p-values of the original findings and replication outcomes. The dataset is made available through the R package “pooledmaRket” and can be used to further study community beliefs towards replications outcomes as elicited in the surveys and prediction markets.

4 Discussion

In this paper, we investigate the forecasting performance of two different procedures to elicit beliefs about replication of scientific studies: prediction markets and prediction survey. We pooled the forecasting data using these two methods from four published papers in which forecasters, mainly researchers and scholars in the social sciences, estimated the probability that a tested hypothesis taken from a paper published in scientific journals would replicate. We find that the prediction markets correctly identify replication outcomes 73% of the time (75/103), while the prediction surveys are correct 66% of the time (68/103). Both the prediction market estimates, and the surveys-based estimates are highly correlated with the replication outcomes of the studies selected for replication (Pearson correlation = 0.581 and = 0.564, respectively), suggesting that studies that replicate can be distinguished from studies that do not successfully replicate. However, both the forecasts elicitation methods tend to overestimate the realized replication rates, and beliefs about replication are on average about ten percentage units larger than the observed replication rate. The results suggest that peer beliefs can be elicited to obtain important information about reproducibility, but the systematic overestimation of the replication probability also imply that there is room for calibrating the elicited beliefs to further improve predictions. In terms of comparing which elicitation method performs better in the task of aggregating beliefs and providing more accurate forecasts, our results suggest that the markets perform somewhat better than the survey especially if evaluating based on absolute prediction error.

We confirmed previous results which indicated that p-values, which can be interpreted as a measure for the strength of evidence, are informative in respect to replication success. There is, however, some debate on the appropriateness of interpreting p-values as a measure of strength of evidence [3536]. While Fisher viewed smaller p-values as stronger evidence against the null hypothesis [37], others methods have been proposed to be more suitable for quantifying the strength of evidence [3839]. Our findings thus provide some context for interpreting p-values as strength of evidence by demonstrating a relationship with replicability, but further research could extend this by analysing the relation between replication outcomes with other measures for the strength of evidence such as effect sizes. In addition, a meta-analysis provides no evidence for the relation between the p-value and replication outcomes to differ from project to project (or between academic fields). Conversely there is suggestive evidence of heterogeneity in the relationship between forecast and replication outcome, as shown by the meta-analysis of the correlations from the different projects. This heterogeneity may arise from differences in study design, the forecasters involved, or some fields may be easier to forecast than others. However, with only a small number of studies used in our meta-analyses, further data are required for more conclusive results.

The data and results presented in this paper can be used for future forecasting projects that are either planned or in progress [14], by informing experimental design and forecasting aggregation. The results can also be used to evaluate the predictive performance of prediction markets against other methods [333440]. The pooled dataset presents opportunities for other researchers investigate replicability of scientific research, human forecasts and their intersection, as well as providing a benchmark for any further replication-based markets.

Unexpected losses of local teams lead to a small decrease in the number of births nine months thereafter due to reduced short-term sexual interest and intercourse

Soccer Scores, Short-Term Mood and Fertility. Fabrizio Bernardi & Marco Cozzani. European Journal of Population, Apr 14 2021,

Abstract: Previous research has shown that seemingly irrelevant events such as unexpected outcomes in sporting events can affect mood and have relevant consequences for episodes of crime and violence, investing behavior and political preferences. In this article, we test whether mood shocks associated with unexpected results in soccer matches in Spain affect fertility. We use data on betting odds and actual scores to define mood shocks and link them to births by month and province in Spain, between 2001 and 2015. We find that unexpected losses of local teams lead to a small decrease in the number of births nine months thereafter. The effect is larger for more unexpected losses, in those provinces with the largest amount of support for the local team and robust to a number of placebo tests. We argue that these results are consistent with the gain–loss asymmetry predicted by prospect theory.


Previous studies have documented that seemingly irrelevant events may have important consequences for political preferences and opinions, for risk-taking economic decisions and for episodes of crime and violence (Card and Dahl 2011; Edmans et al. 2007; Healy et al. 2010; Munyo and Rossi 2013). These findings have been interpreted as evidence that changes in mood spread to otherwise unrelated dimensions such as evaluation of politics or of economic risk and can trigger other types of behaviors. In this article, we build on this literature and test the hypothesis that mood shocks might influence fertility behavior. To this end, we analyze the universe of births data in Spain between 2001 and 2015 and focus on mood shocks arising from soccer scores in Spain. We compare betting odds and actual outcomes of soccer games in Spain to identify exogenous mood shocks around expected outcomes.

Two previous academic articles on the effect of sport events on fertility have produced contradictory findings. The anecdotal claim of an “Iniesta generation” following the last-minute goal by the Barcelona midfielder in the UEFA Champions league semifinal against Chelsea is confirmed by Montesinos et al. (2013), while no evidence of “Super Bowl Babies” is found by Hayward and Rybińska (2017). What these two studies have in common is that they both focus on the supposed positive effect of success in a major sport event on fertility. In our study, we enlarge the explicative framework to also consider the consequence of losses. We find that an unexpected loss by the most popular soccer team in a Spanish province leads to a reduction of 0.8% in the number of births nine months later in that province. We do not find an opposite effect for unexpected wins. This finding is consistent with an asymmetric hypothesis drawn from prospect theory, stating that mood changes arise due to deviations from expected outcomes, with losses having larger effect than wins. A possible way to reconcile our findings and those by Hayward and Rybińska (2017) and Montesinos et al. (2013) is that a sport victory has to come as really unexpected with an unique collective celebration to produce an increase in the number of births, as it might have been the case for the agonic victory of FC Barcelona against Chelsea, associated with the Iniesta generation, and less so for the Super Bowl games whose outcomes tend to be more equalized a priori.

From a quantitative point of view, the point estimate of our main finding is very small. For instance, the 0.8 percent reduction in the number of births in a given province associated with one unexpected loss of the local soccer in team nine months earlier that we have documented corresponds on average to a reduction of about 49 births for each unexpected loss in a given month for the province of Madrid. The estimated effect, therefore, does not entail any consequences for the aggregate fertility rate in Spanish provinces. The decrease in the number of births nine months after an unexpected loss by the local team is likely to be compensated in the following months, by those couples who were planning to have a child. Even small-sized effect can, however, entail theoretical relevance (Elliott and Granger 2004; Bernardi et al. 2017). First, our key finding supports the idea that emotions and mood can be important determinants for fertility. Scholars should then consider how to include emotions into the increasingly popular models of planned behavior to study fertility (Ajzen and Klobas 2013; Mencarini et al. 2015). Work in close-by disciplines can provide some fruitful interdisciplinary inspiration in that direction (Elster, 1998; Massey, 2002). Second, our main finding also provides support for the prediction of prospect theory beyond its most common applications in finance, insurance and consumption-saving decisions (Barberis, 2013).

Methodologically, our study adds to a body of studies that have investigated the effect of subjective well-being on fertility. Moods and emotions are an important component of subjective well-being (Diener et al. 1999). There is now some evidence that happier people are more likely to have children and conversely that stress and poor mood might cause infertility (Aassve et al. 2012; Cetre et al. 2016; Greil 1997; Le Moglie et al. 2015; Parr 2010). Although our results refer only to short-lived mood shock, they provide critical evidence that supports a causal interpretation of the association previously found between happiness and fertility.

A major limitation of our study that makes us interpret these suggestive results with caution is that we cannot observe the intervening mechanisms between soccer scores and mood shock and between the latter and reduction in number of births. In a direct extension of this work, one could measure mood shocks with a sentiment analysis using Twitter data on province base (Mencarini et al. 2019). One could also focus on the intervening mechanism between mood shocks and fertility, i.e., reduction in sexual desire and intercourse. One could then study the effect of mood shock on some proxies for sexual arousal and intercourse, such as the internet access to porn sites (Markey and Markey 2010) or consumption of condoms and morning-after pills.

Still, these additional analyses with different indicators for mood shocks and proxies for sexual intercourse at the province level would still suffer from a major limitation that we also face in this current work, namely that we use macro-level data to test a micro-level mechanism. In this respect, future research could focus on physiological mechanisms (Bernhardt et al. 1998; van der Meij el al. 2012) and test whether testosterone change following vicarious experience of unexpected wins and losses is indeed asymmetric, so that a hormone change after unexpected losses is larger than the increase after unexpected wins. One could also look at variations in sexual interest and behaviors (Bancroft et al. 2003; Janssen et al. 2013) and analyze whether and how mood shocks related to soccer outcomes (or any other event that might affect mood) affect sexual interest and intercourse.

Humans sometimes picture themselves from an external vantage point, particularly when they consider events in a broader context or care about their reputation

Picturing yourself: a social-cognitive process model to integrate third-person imagery effects. Zachary Adolph Niese,Richard P. Eibach &Lisa K. Libby. Journal of Cognitive Psychology, Apr 13 2021.

Rolf Degen's take:

Abstract: People have a fascinating capacity to picture their actions from an external vantage point. Much of the research on this third-person imagery has focused on the specific effects it has on cognition due to the elements of episodic experience that it lacks relative to first-person imagery. Other research focuses on the information that the third-person provides that first-person imagery lacks. We propose a more systematic approach that conceptualises how third-person imagery’s various effects interrelate due to a common underlying social-cognitive function. Specifically, we outline an integrative model proposing that third-person and first-person imagery cause people to adopt qualitatively distinct processing styles. This model explains many of the diverse effects that have been documented in the literature and helps reconcile seemingly discrepant findings. We conclude with recommendations for strategies to more systematically investigate the functions of visual perspective in mental imagery to build more comprehensive understanding of this phenomenological variable.

KEYWORDS: visual imagery perspectivethird-person imageryprocessing styles

An ant can increase and decrease its brain size, according to its reproductive status

Reversible plasticity in brain size, behaviour and physiology characterizes caste transitions in a socially flexible ant (Harpegnathos saltator). Clint A. Penick, Majid Ghaninia, Kevin L. Haight, Comzit Opachaloemphan, Hua Yan, Danny Reinberg and Jürgen Liebig. Proceedings of the Royal Society B, April 14 2021.

Abstract: Phenotypic plasticity allows organisms to respond to changing environments throughout their lifetime, but these changes are rarely reversible. Exceptions occur in relatively long-lived vertebrate species that exhibit seasonal plasticity in brain size, although similar changes have not been identified in short-lived species, such as insects. Here, we investigate brain plasticity in reproductive workers of the ant Harpegnathos saltator. Unlike most ant species, workers of H. saltator are capable of sexual reproduction, and they compete in a dominance tournament to establish a group of reproductive workers, termed ‘gamergates'. We demonstrated that, compared to foragers, gamergates exhibited a 19% reduction in brain volume in addition to significant differences in behaviour, ovarian status, venom production, cuticular hydrocarbon profile, and expression profiles of related genes. In experimentally manipulated gamergates, 6–8 weeks after being reverted back to non-reproductive status their phenotypes shifted to the forager phenotype across all traits we measured, including brain volume, a trait in which changes were previously shown to be irreversible in honeybees and Drosophila. Brain plasticity in H. saltator is therefore more similar to that found in some long-lived vertebrates that display reversible changes in brain volume throughout their lifetimes.

4. Discussion

Workers of Harpegnathos saltator exhibited reversible changes in brain size similar to that found in relatively long-lived vertebrate species. Changes in brain volume observed in vertebrates generally track seasonal reproductive cycles and are triggered by reproductive hormone cascades [9]. Likewise, brain changes in H. saltator also track the reproductive status and are associated with changes in reproductive hormone levels [20,21] and the expression of key regulatory genes [42]. Changes in the vertebrate brain include the seasonal addition of new neurons [54], which we did not specifically measure here, but changes in total and region-specific brain volumes are comparable.

[Figure 6. Correlated plasticity in brain, behaviour, and physiology between reproductive and non-reproductive workers. (Online version in colour.)]

Task or experience-dependent plasticity of brain compartments has been demonstrated in various insects, including honeybees, ants, paper wasps, and moths (e.g. [11,34,5557]). In H. saltator, gamergate brains were 19% smaller than the brains of foragers on average, which is in line with predictions that brain size should be reduced to divert metabolic resources to reproduction [12,13]. Even compared to comparatively younger inside workers, gamergate optic lobes were 24% smaller, suggesting they may not simply retain the brain size of young nurse workers, but most likely experience region-specific brain volume reduction. When gamergates of H. saltator were reverted back to non-reproductive status, their brains re-expanded and matched that of forager brains. Foraging requires the ability to orient towards the nest and to attack and retrieve live prey items, all of which requires higher cognitive processing. The observed reduction in central brain volume of gamergates and the subsequent expansion in reverted gamergates suggest it is used for the more demanding cognitive abilities of foraging [58]. Changes in the central brain of H. saltator, which includes the mushroom body, are consistent with results from other social insects [59]. In carpenter ants, foragers that perform cognitively demanding tasks exhibit an increase of more than 50% of mushroom body neuropile volume [11] and a similar pattern is found in the mushroom body of honeybees [60].

The pattern of size differences in the optic lobe of H. saltator suggests a programmed rather than experience-dependent change in brain volume. Gamergates displayed significantly smaller optic lobes than inside workers and foragers, both of which had equally large optic lobes. Gamergates were still exposed to light and thereby received visual stimulation from their nest-mates in our laboratory settings, so sensory deprivation is an unlikely cause for the size differences we observed. Given that gamergates do not rely on optic information under natural conditions, a reproduction-dependent size reduction seems most likely. The intermediate optic lobe size of reverted gamergates relative to gamergates and non-reproductive workers suggests a presumably slower reversion speed of the optic lobe compared to the central brain. However, the size reductions of the optic lobes and of the central brain compared to reverted gamergates both suggest this brain size reduction is an energy-saving mechanism as proposed previously [12,13].

The reversibility of changes in brain size in H. saltator contrasts with results in the honeybee and in Drosophila. Brain size in honeybees increases as nurse workers transition to foragers, but when foragers are reverted to nurse status, they do not show a decrease in brain volume [32]. Honeybee foragers in the study by Fahrbach et al. [32] were only reverted back to nurses for 5 days, while gamergates in the present study were reverted for 6–8 weeks, which may explain why brain changes were observed in our study but not in previous studies on honeybees. In addition, honeybee foragers typically only live for a matter of weeks, and there is no biological ‘reason' for why they should fully revert to nurse status—in a colony of 50 000 bees, foragers can easily be replaced by new workers. By contrast, H. saltator colonies are small (usually less than 100 individuals), and each worker represents a more valuable resource in terms of their relative contribution to colony productivity. Studies in Drosophila have looked at region-specific changes in brain size associated with adult age, and while the medulla of the optic lobe in D. melanogaster increases in size with age, sensory deprived medullae do not increase in size and this lack of growth seems to be irreversible later in life [33]. This difference in brain plasticity corroborates differences in the plasticity of the antennal lobe between ants and Drosophila. When the odorant receptor co-receptor (orco) was knocked out in ants, the antennal lobes showed a significant reduction in two ant species [61,62]. A similar morphological change was not present in Drosophila when orco was knocked out, which suggests a hardwired mode of olfactory glomeruli formation in the Drosophila antennal lobe [63] and potentially major differences in brain development between Drosophila and ants.

Along with reversion in brain size, we found behavioural and physiological reversions that include the ovarian activity, venom production, CHC profile, and expression of associated genes (figure 6). Combined changes in physiological traits and underlying gene expression levels demonstrate that the changes we observed in reverted gamergates were not random, but instead matched a clearly defined worker phenotype. If we had observed a mix of different physiological changes that were inconsistent with the worker phenotype, then we might have expected these changes to be driven by isolation stress alone. The effects of chronic stress are generally expected to increase the allostatic load and result in decreases in body mass and brain function [64], yet contrary to this prediction, we observed increases in brain size and venom production in reverted gamergates. Likewise, changes in gene expression of ELOV, which is involved in fatty acid elongation, and Vg, the vitellogenin egg yolk precursor, were consistent with downstream physiological responses of CHC profiles and ovarian activity.

The observed reversibility in phenotypic plasticity in H. saltator gamergates that transition back to non-reproductive workers is present despite the rarity of such events. Naturally, queens and gamergates reproduce until senescence and do not substantially contribute to foraging after the loss of status. Thus, there would appear to be little selective pressure to keep reproductive specialization reversible. However, reversibility of phenotypic plasticity could be maintained to allow workers the return to forager status after they have lost a reproductive tournament. Dominance tournaments last up to 40 days in H. saltator, and initially up to half the workforce of a colony may compete [41]. Physiological changes begin shortly after tournaments are initiated [21,42], and reversibility may allow workers to return to forager status without suffering long-term effects associated with the early transition period to reproductive status. Among social insects, lower termites offer another rare example of reversible plasticity, in which individuals develop regressively from nymphal instars to ‘worker' instars that lack wing buds [65]. The precise reason why regressive moults occur in lower termites is not understood, but it does have parallels to reversible plasticity in H. saltator. In both H. saltator and lower termites, reversible plasticity allows individuals to retain flexibility in shifting between non-reproductive and reproductive pathways.