Tuesday, June 22, 2021

Individuals Who Own Sex Dolls: Had more sexual fantasies related to coercion (biastophilia), but lower offense proclivity; were also more likely to see women as unknowable; have more stable negative mood

Harper, Craig A., Rebecca Lievesley, and Katie Wanless. 2021. “Exploring the Psychological Characteristics of Individuals Who Own Sex Dolls.” PsyArXiv. June 22. doi:10.31234/osf.io/fxznv

Abstract: The ownership of sex dolls has become an increasingly controversial social issue over the last five-to-ten years, with many in society (and academia) calling for the criminalization of such dolls. At the root of these calls is the implicit (and often explicit) assumption that sex doll ownership contributes to increases in social objectification of women, and sexual offense risk among doll owners. However, there are yet to be any empirical examinations of these claims. In this work we compare the psychological characteristics of sex doll owners (n = 158) and non-owner controls (n = 135). Contrary to widely held social attitudes, we found no substantive differences in sexual objectification between the two groups. Doll owners typically had more sexual fantasies related to coercion (biastophilia), but lower offense proclivity, than controls. Owners were also more likely to see women as unknowable, have less secure attachment styles, and more stable negative mood. We begin to build a psychological profile of sex doll ownership, before highlighting the need for more evidence-informed social debates about the use of sex dolls in modern society.

The extent to which the less powerful citizens within a country expect & accept that power is distributed unequally shows negative association with both Covid-19 morbidity & mortality, ensuring conformity to prescribed behaviors

Impact of Societal Culture on Covid-19 Morbidity and Mortality across Countries. Rajiv Kumar. Journal of Cross-Cultural Psychology, June 15, 2021. https://doi.org/10.1177/00220221211025100

Abstract: Researchers have begun exploring the impact of societal culture on Covid-19 outcomes (morbidity and mortality). However, emerging findings need integration with prior literature on societal culture and infectious diseases. Moreover, accumulation of knowledge warrants an update while overcoming certain limitations of samples as well as construct validity concerns. Accordingly, hypotheses are derived based on extant evidence proposing the impact of certain cultural practices on Covid-19 outcomes across countries. These hypotheses are tested using the cultural practice scores from GLOBE studies after controlling for certain covariates identified in literature. Multiple regression results reveal that societal culture significantly explains Covid-19 outcomes beyond the explanation due to control variables. Specifically, power distance and institutional collectivism show negative association with both Covid-19 morbidity and mortality. Additionally, performance orientation shows negative association with Covid-19 morbidity. It appears that power distance may ensure conformity to prescribed behaviors and features of performance orientation may facilitate swift and effective containment of Covid-19 cases. The significance of institutional collectivism—but not in-group collectivism—emerging as the form of collectivism showing negative association with Covid-19 outcomes is also discussed.

Keywords: Covid-19, culture, GLOBE, power distance, collectivism, institutional collectivism, performance orientation

Beards Increase the Speed, Accuracy, and Explicit Judgments of Facial Threat

Beards Increase the Speed, Accuracy, and Explicit Judgments of Facial Threat. Barnaby J. W. Dixson, Claire L. Barkhuizen & Belinda M. Craig. Adaptive Human Behavior and Physiology, Jun 22 2021. https://rd.springer.com/article/10.1007/s40750-021-00169-1


Objectives: To test whether intra-sexual selection has influenced perceptions of male facial hair. We predicted that beards would increase the speed and accuracy of perceptions of angry but not happy facial expressions. We also predicted that bearded angry faces would receive the highest explicit ratings of masculinity and aggressiveness, whereas higher prosociality ratings would be ascribed to clean-shaven happy faces.

Methods: A total of 106 participants, ranging from 17 to 59 years of age (M = 27.27, SD = 10.03); 59 were female and 47 were male (44.3%) completed an emotion categorization tasks and an explicit ratings task. Participants viewed faces of the same men when bearded, clean-shaven, and 10 days of natural growth (i.e. stubble) when posing angry and happy facial expressions.

Results: Angry facial expressions were categorised most rapidly and with the greatest accuracy on bearded faces, followed by faces with stubble then clean-shaven faces. Conversely, happy facial expressions were categorised most rapidly and with the greatest accuracy on clean-shaven faces, followed by stubbled faces then bearded faces. Irrespective of facial expression, full bearded faces received the highest ratings of masculinity followed by faces with stubble then clean-shaven faces. Aggressiveness ratings were highest for angry faces with full beards, followed by angry faces with stubble, with clean-shaven angry faces receiving the lowest ratings. In contrast to our prediction, bearded smiling faces were rated as significantly more prosocial than stubbled and clean-shaven smiling faces.

Conclusions: These findings contribute further evidence that men’s beardedness represents an intra-sexually selected badge of status that enhances nonverbal threat potentially by augmenting underlying masculine facial structures.

Check also Cross-Cultural Variation in Men’s Beardedness. Barnaby J. W. Dixson & Anthony J. Lee. Adaptive Human Behavior and Physiology (2020). Sep 1 2020. https://www.bipartisanalliance.com/2020/09/mens-decision-to-augment-their.html

And: Mothers are sensitive to men's beards as a potential cue of paternal investment. Barnaby J. W. Dixson, Siobhan Kennedy-Costantini, Anthony J. Lee, Nicole L. Nelson. Hormones and Behavior, Volume 113, July 2019, Pages 55-66. https://www.bipartisanalliance.com/2019/05/preferences-for-beards-when-judging.html

Precision-grasping muscles & and power-grasping muscles... Reconstructing occupations thru muscles to allow us to look into our ancestral past

New horizons in reconstructing past human behavior: Introducing the “Tübingen University Validated Entheses-based Reconstruction of Activity” method. Fotios Alexandros Karakostis, Katerina Harvati. Evolutionary Anthropology: Issues, News, and Reviews, March 25 2021. https://doi.org/10.1002/evan.21892

Abstract: An accurate reconstruction of habitual activities in past populations and extinct hominin species is a paramount goal of paleoanthropological research, as it can elucidate the evolution of human behavior and the relationship between culture and biology. Variation in muscle attachment (entheseal) morphology has been considered an indicator of habitual activity, and many attempts have been made to use it for this purpose. However, its interpretation remains equivocal due to methodological shortcomings and a paucity of supportive experimental data. Through a series of studies, we have introduced a novel and precise methodology that focuses on reconstructing muscle synergies based on three-dimensional and multivariate analyses among entheses. This approach was validated using uniquely documented anthropological samples, experimental animal studies, histological observations, and geometric morphometrics. Here, we detail, synthesize, and critically discuss the findings of these studies, which overall point to the great potential of entheses in elucidating aspects of past human behavior.


Muscle attachment sites (i.e., “entheses”) are the areas of the bone where muscles, tendons, or ligaments attach.1 They represent the only direct evidence of the musculotendinous, soft tissue system on skeletal remains. As such, they are commonly thought to broadly reflect muscular activity and have been used for reconstructing habitual physical activity among past human populations and extinct hominin species.2-4 The methods of entheseal analysis can broadly be divided into those relying on observational scoring systems describing robusticity or potentially pathological entheseal changes (EC) of the surface on the one hand3-7; and those quantifying entire entheseal size or shape based on three-dimensional (3D) surface models on the other.8-12 The interpretations of the latter approaches typically rely on the assumption that entheseal morphology may vary with changes of biomechanical load.21314 However, most visual scoring systems for analyzing these activity markers have often been criticized for a lack of precision and statistical rigor.1516 At the same time, several studies focusing on entheseal 3D morphology in laboratory animals and human cadavers have found no evidence to support the hypothesized functional character of entheses,1217-19 questioning their reliability in reconstructing past behavior.

In this framework, we recently put forth a new and repeatable methodology for analyzing entheses based on multivariate analyses targeting the reconstruction of muscle synergy groups.10 As our approach relies on 3D surface area measurements of entheses without potential pathological lesions (i.e., distinctive osteophytic or osteolytic lesions),10 it can be considered more comparable to visual scoring techniques focusing on entheseal robusticity, rather than those incorporating potentially pathological ECs.2021 Here, we conduct a critical review of the interdisciplinary body of literature that validated this 3D approach on the basis of anthropological samples with uniquely detailed occupational documentation22 as well as two blindly-conducted experimental studies on animals.2324 These results are discussed together with our relevant findings from histological research on human cadaveric material25 and 3D geometric morphometric applications for analyzing muscle attachment form.11 Taken together, our synthesis supports the new approach's efficiency as an important tool for reconstructing past human behavior,26 while also describing its limitations and potential pathways for improvement in the future. We term this new methodology the Tübingen University Validated Entheses-based Reconstruction of Activity (hereafter V.E.R.A.).

1.1 Types of entheses and biomechanical implications

Muscle attachment sites are broadly categorized as fibrous or fibrocartilaginous, depending on the nature of their insertion to the bone.1 In fibrous attachments, the muscle/tendon or ligament attaches directly onto the periosteum, which is itself attached to the bone via Sharpey fibers.2728 Fibrocartilaginous entheses, on the other hand, describe a gradient structure of attachment involving four transition zones: tendon, uncalcified fibrocartilage, calcified fibrocartilage, and bone.1272930 Some studies of EC scores analyze fibrous and fibrocartilaginous entheses together.20 However, most researchers consider fibrous entheses less useful for reconstructing physical activity, mainly due to the poor understanding of their reaction to biomechanical stress, lower measurement repeatability, weak correlation with occupational types, lower level of bilateral asymmetry in the upper limbs, and higher correlation with body size proxies.5631-34 This viewpoint is also supported by histological research suggesting that, in fibrous entheses (typically along the metaphysis or diaphysis of long bones), biomechanical forces seem to be dissipated over a wider area of attachment.1727 By contrast, in fibrocartilaginous entheses (typically at apophyses or epiphyses of long bones), all biomechanical stress is concentrated on to relatively smaller attachment surfaces, potentially leading to higher stress energy density and greater deformations of the comparatively thin cortical layer within these areas.11729 Nonetheless, it should be emphasized that recent histological research showed that fibrous and fibrocartilaginous attachments may co-exist in the same enthesis,273536 suggesting that the nature of muscle attachment to bone is much more complex than previously believed.

The anatomical area where an enthesis is located is also considered important, given that the nature and intensity of the biomechanical forces at play are bound to differ across the skeleton. As a result, there is substantial variation among entheses both in gross morphology and micro-architecture.52530 From a biomechanical point of view, entheseal variability has been suggested to be broadly associated with an interaction between body weight (compressive) and muscle tendon (tensile) forces, which substantially vary across anatomical regions.25303738 In this regard, the hand shares the smallest proportion of body weight in the human skeleton,39 suggesting that perhaps the effects of muscle recruitment on entheses may possibly be greater in hand bones compared to elements from high-weight-bearing anatomical areas.25 Based on this concept, as well as on the fundamental role of manual tasks in human daily activities and subsistence strategies,40 most of our research to date has focused on the entheses of the human hand. 

Hysterical reaction to "poorly understood" consequences? Fourth author thinks this "might be the most important paper of my career;" addresses "the harm wrought by dramatically restructuring human communication o[n] the span of a decade, with no aim other than selling ads"

Stewardship of global collective behavior. Joseph B. Bak-Coleman, M A, W B, Carl T. Bergstrom et al. Proceedings of the National Academy of Sciences, July 6, 2021 118 (27) e2025764118; https://doi.org/10.1073/pnas.2025764118

His take... Carl T. Bergstrom on Twitter: We have a new paper out in PNAS today, in which we address the harm wrought by dramatically restructuring human communication of the span of a decade, with no aim other than selling ads. It might be the most important paper of my career

Abstract: Collective behavior provides a framework for understanding how the actions and properties of groups emerge from the way individuals generate and share information. In humans, information flows were initially shaped by natural selection yet are increasingly structured by emerging communication technologies. Our larger, more complex social networks now transfer high-fidelity information over vast distances at low cost. The digital age and the rise of social media have accelerated changes to our social systems, with poorly understood functional consequences. This gap in our knowledge represents a principal challenge to scientific progress, democracy, and actions to address global crises. We argue that the study of collective behavior must rise to a “crisis discipline” just as medicine, conservation, and climate science have, with a focus on providing actionable insight to policymakers and regulators for the stewardship of social systems.

Keywords: collective behaviorcomputational social sciencesocial mediacomplex systems

Collective behavior historically referred to instances in which groups of humans or animals exhibited coordinated action in the absence of an obvious leader (14): from billions of locusts, extending over hundreds of kilometers, devouring vegetation as they move onward; to schools of fish convulsing like some animate fluid while under attack from predators; to our own societies, characterized by cities, with buildings and streets full of color and sound, alive with activity. The characteristic feature of all of these systems is that social interactions among the individual organisms give rise to patterns and structure at higher levels of organization, from the formation of vast mobile groups to the emergence of societies with division of labor, social norms, opinions, and price dynamics.

Over the past few decades “collective behavior” has matured from a description of phenomena to a framework for understanding the mechanisms by which collective action emerges (37). It reveals how large-scale “higher-order” properties of the collectives feed back to influence individual behavior, which in turn can influence the behavior of the collective, and so on. Collective behavior therefore focuses on the study of individuals in the context of how they influence and are influenced by others, taking into account the causes and consequences of interindividual differences in physiology, motivation, experience, goals, and other properties.

The multiscale interactions and feedback that underlie collective behavior are hallmarks of “complex systems”—which include our brains, power grids, financial markets, and the natural world (89). When perturbed, complex systems tend to exhibit finite resilience followed by catastrophic, sudden, and often irreversible changes in functionality (910). Across a wide range of complex systems, research has highlighted how anthropogenic disturbance—technology, resource extraction, and population growth—is an increasing, if not dominant, source of systemic risk. Yet, scientific research on how complex systems are impacted by human technology and population growth has largely focused on the threats that these pose to the natural world (1113). We have a far poorer understanding of the functional consequences of recent large-scale changes to human collective behavior and decision making. Our social adaptations evolved in the context of small hunter-gatherer groups solving local problems through vocalizations and gestures. Now we face complex global challenges from pandemics to climate change—and we communicate on dispersed networks connected by digital technologies such as smartphones and social media.

With increasingly strong links between ecological and sociological processes, averting catastrophe in the medium term (e.g., coronavirus) and the long term (e.g., climate change, food security) will require rapid and effective collective behavioral responses—yet it remains unknown whether human social dynamics will yield such responses (1417). In addition to existential ecological and climatic threats, human social dynamics present other challenges to individual and collective wellbeing, such as vaccine refusal, election tampering, disease, violent extremism, famine, racism, and war.

Neither the evolutionary nor the technological changes to our social systems have come about with the express purpose of promoting global sustainability or quality of life. Recent and emerging technologies such as online social media are no exception—both the structure of our social networks and the patterns of information flow through them are directed by engineering decisions made to maximize profitability. These changes are drastic, opaque, effectively unregulated, and massive in scale.

The emergent functional consequences are unknown. We lack the scientific framework we would need to answer even the most basic questions that technology companies and their regulators face. For instance, will a given algorithm for recommending friends—or one for selecting news items to display—promote or hinder the spread of misinformation online? We do not have access to a theory-driven, empirically verified body of literature to inform a response to such a question. Lacking a developed framework, tech companies have fumbled their way through the ongoing coronavirus pandemic, unable to stem the “infodemic” of misinformation that impedes public acceptance of control measures such as masks and widespread testing (18).

In response, regulators and the public have doubled down on calls for reforming our social media ecosystem, with demands ranging from increased transparency and user controls to legal liability and public ownership. The basic debate is an ancient one: Are large-scale behavioral processes self-sustaining and self-correcting, or do they require active management and guidance to promote sustainable and equitable wellbeing (219)? Historically, these questions have been addressed in philosophical or normative terms. Here, we build on our understanding of disturbed complex systems to argue that human social dynamics cannot be expected to yield solutions to global issues or to promote human wellbeing without evidence-based policy and ethical stewardship.

The situation parallels challenges faced in conservation biology and climate science, where insufficiently regulated industries optimize profits while undermining the stability of ecological and earth systems. Such behavior created a need for urgent evidence-based policy in the absence of a complete understanding of the systems’ underlying dynamics (e.g., ecology and geosciences). These features led Michael Soulé to describe conservation biology as the “crisis discipline” counterpoint to ecology—an analogy to the relationship between medicine and comparative physiology (20). Crisis disciplines are distinct from other areas of urgent, evidenced-based research in their need to consider the degradation of an entire complex system—without a complete description of the system’s dynamics. We feel that the study of human collective behavior must become the crisis discipline response to changes in our social dynamics.

Because human collective behavior is the result of processes that span temporal, geographical, and organizational scales, addressing the impact of emerging technology on global behavior will require a transdisciplinary approach and unprecedented collaboration between scientists across a wide range of academic disciplines. As our societies are increasingly instantiated in digital form, once-mathematical abstractions of social processes—networks are one prominent example—become very real parts of daily life (2123). These changes present new challenges, as well as opportunities for measurement and intervention. Disciplines within and beyond the social sciences have access to techniques and ways of thinking that expand our ability to understand and respond to the effects of communication technology. We believe such a collaboration is urgently needed.

In what follows, we begin by framing human collective behavior as a complex adaptive system shaped by evolution, a system that much like our natural world has entered a heavily altered and likely unsustainable state (142425). We highlight how communication technology has restructured human social networks, expanding, reorganizing, and coupling them to technological systems. Drawing on insight from complexity science and related fields, we discuss observed and potential consequences. Next, we describe how a transdisciplinary approach is required for actionable insight into the stewardship of social systems. Finally, we discuss some of the key ethical, scientific, and political challenges.


In lower-income countries, the economic contractions that accompany lockdowns to contain the spread of COVID-19 can increase child mortality, counteracting the mortality reductions achieved by the lockdown

The Intergenerational Mortality Tradeoff of COVID-19 Lockdown Policies. Lin Ma, Gil Shapira, Damien de Walque, Quy-Toan Do, Jed Friedman & Andrei A. Levchenko. NBER Working Paper 28925. Jun 2021. DOI 10.3386/w28925

Abstract: In lower-income countries, the economic contractions that accompany lockdowns to contain the spread of COVID-19 can increase child mortality, counteracting the mortality reductions achieved by the lockdown. To formalize and quantify this effect, we build a macro-susceptible-infected-recovered model that features heterogeneous agents and a country-group-specific relationship between economic downturns and child mortality, and calibrate it to data for 85 countries across all income levels. We find that in low-income countries, a lockdown can potentially lead to 1.76 children’s lives lost due to the economic contraction per COVID-19 fatality averted. The ratio stands at 0.59 and 0.06 in lower-middle and upper-middle income countries, respectively. As a result, in some countries lockdowns actually can produce net increases in mortality. The optimal lockdowns are shorter and milder in poorer countries than in rich ones, and never produce a net mortality increase.

From 2019... Clearing the path for an anti-imperialist feminist universalism by showing how feminist complicity in imperialism is not caused by the fact of having universalist normative commitments

From 2019... Is Universalism the Cause of Feminist Complicity in Imperialism? Serene Khader. Health, Well-being & Society, Volume 35, 2019, Pages 21-37. https://doi.org/10.5840/socphiltoday20193569

Abstract: Global and transnational feminist praxis has long faced a seemingly inexorable dilemma. Universalism is often charged with causing feminist complicity in imperialism. In spite of this, it seems clear that feminists should not embrace relativism; feminism is, after all, a view about how certain types of treatment based on gender are wrong. This article clears the path for an anti-imperialist feminist universalism by showing how feminist complicity in imperialism is not caused by the fact of having universalist normative commitments. What I call “missionary feminism” stems more from ethnocentrism, justice monism, and idealizing and moralizing ways of seeing that associate Western culture with morality (and thus prevent Western culture and Western intervention from becoming objects of normative scrutiny) than from universalism about the value of gender justice.

The first large-scale assessment of ravens' cognitive abilities suggests that, by 4 months of age, ravens do about as well as adult chimps and orangutans on tests of causal reasoning, social learning, theory of mind, &c.

Ravens parallel great apes in physical and social cognitive skills. Simone Pika, Miriam Jennifer Sima, Christian R. Blum, Esther Herrmann & Roger Mundry. Scientific Reports volume 10, Article number: 20617, Dec 10 2020. https://www.nature.com/articles/s41598-020-77060-8

Abstract: Human children show unique cognitive skills for dealing with the social world but their cognitive performance is paralleled by great apes in many tasks dealing with the physical world. Recent studies suggested that members of a songbird family—corvids—also evolved complex cognitive skills but a detailed understanding of the full scope of their cognition was, until now, not existent. Furthermore, relatively little is known about their cognitive development. Here, we conducted the first systematic, quantitative large-scale assessment of physical and social cognitive performance of common ravens with a special focus on development. To do so, we fine-tuned one of the most comprehensive experimental test-batteries, the Primate Cognition Test Battery (PCTB), to raven features enabling also a direct, quantitative comparison with the cognitive performance of two great ape species. Full-blown cognitive skills were already present at the age of four months with subadult ravens’ cognitive performance appearing very similar to that of adult apes in tasks of physical (quantities, and causality) and social cognition (social learning, communication, and theory of mind). These unprecedented findings strengthen recent assessments of ravens’ general intelligence, and aid to the growing evidence that the lack of a specific cortical architecture does not hinder advanced cognitive skills. Difficulties in certain cognitive scales further emphasize the quest to develop comparative test batteries that tap into true species rather than human specific cognitive skills, and suggest that socialization of test individuals may play a crucial role. We conclude to pay more attention to the impact of personality on cognitive output, and a currently neglected topic in Animal Cognition—the linkage between ontogeny and cognitive performance.


Here, we provide the first quantitative, large-scale investigation of physical and social cognitive skills in a large-brained songbird species—ravens. We particularly examined the effect of development on cognitive performance, and revisited the claim that corvids rival non-human primates in their cognitive abilities34,40. To achieve these goals, we fine-tuned one of the most elaborate large-scale cognitive test batteries—the PCTB10—to raven features. The results demonstrated that our ravens showed comparable cognitive performance in the domains of social and physical cognition. The performance was highest in tests of quantitative and lowest in tasks of spatial skills. Full-blown cognitive skills were already present at the age of four months, and did not significantly change within the investigated time window. The quantitative cross-species comparison showed that, with the exception of spatial skills, the cognitive performance of our birds was on par with those of orang-utans and chimpanzees.

In the following, we will discuss these findings in detail.

Cognitive performance in physical and social cognitive scales

Overall, we found that our ravens’ physical cognitive performance was very similar to their social cognitive performance, with highest performance scores in quantitative skills and lowest performance scores in spatial skills. These results are not in line with our prediction suggesting that ravens perform differently in the domains of physical and social cognition48.

There are several possible explanations. First, differences in physical and social cognitive performance may have simply been obscured by the use of a cognitive test battery designed to tackle potential drivers of human cognitive evolution (see for similar accounts18,89). For instance, task design in the PCTB is anchored in the challenges faced by humans and great apes in their daily lives: to find and locate food, use tools and cope with conspecifics. In contrast, although ravens also have to deal with the challenges of discovering and locating food and manoeuvring in a complex social world, they extensively scatter-hoard carcass meat and are non-habitual tool-users47,90. The test battery may therefore have not been suitable to pinpoint differences in ravens’ physical and social cognitive skills. However, if this explanation is true, we would have expected to find no differences between scales which does not accord with our observations (but see for a recent study on parrots56).

Second, differences in physical and social cognitive performance may only develop later than 16 months of age, and were thus not detected across the four investigated time points. If this explanation were true, we would have expected to find no differences between any tested physical and social cognitive scale across the four different time points, but this was not the case (see Table S4). In addition, recent studies on the development of gaze following skills77 and sensorimotor abilities of ravens72 showed that the general developmental pace is very fast compared to that of other bird and mammal species.

Third, the assumption that ravens have specialized in the social rather than the physical domain48 is simply due to shortage of data. Indeed, due to ravens living in complex societies characterized by fission–fusion dynamics researchers have been fascinated with their social cognitive abilities (see for recent reviews40,49). In addition, studies examining single cognitive aspects have provided many crucial aspects to the remarkable tool-kit of ravens’ physical and social cognitive skills (e.g. 42,46,91,92). Furthermore, ravens are renowned for caching and hoarding food40, combining both sophisticated social (e.g., being highly sensitive to the presence of predators and/or conspecifics that may pilfer caches40,47), and physical cognitive skills (such as remembering where and how much food was cached4047). Hence, our results reveal that ravens are both social and physical intellects, and strengthen recent suggestions that ravens cognitive skills are an expression of general rather than domain specific intelligence36.

In addition, a recent reanalysis of the original PCTB dataset of chimpanzees and children75 using a confirmatory factor analysis (CFA) did not support the original division of the test battery into a social and a physical cognitive domain. Instead, it identified a spatial cognition factor (see also93), suggesting to move beyond the idea that social cognition might be dissociable from physical cognition and evolved separately. The study, thereby, also adds important fuel to the recent debate on cognitive test batteries in animal cognition research (e.g. 18,56,89). For instance, some scholars stress to pay more attention to overlooked task demands that may affect performance (e.g., tracking the movement of human experimenters94), while others suggest to improve test batteries on multiple fronts such as the design of the tasks, the domains targeted and the species tested95. Furthermore, scholars emphasized the importance of addressing the same conceptual question by using tasks that a given species can solve50. In addition, Völter and colleagues96 proposed a psychometric approach involving a three-step program consisting of (1) tasks that reveal signature limits in performance (i.e. the way individuals make mistakes), (2) assessments of the reliability of individual differences in task performance, and (3) multi-trait multi-method test batteries.

The development of cognitive skills

The results showed that our ravens’ cognitive performance did not change across the four investigated time points of four, eight, twelve and 16 months respectively. These findings support the prediction that ravens undergo a relatively rapid cognitive development. They further expand recent results on single cognitive skills and sensorimotor development68,72 in ravens to the physical cognitive scales of Causalities and Quantities and the manifold domain of social cognition. For instance, Schloegl and colleagues77, combining natural observations and behavioural experiments, showed that ravens, shortly after fledging (between 8–15 weeks of age), started to follow the gaze (look where others look) of a conspecific and a human experimenter. This developmental period coincides with ravens still living with their family groups, and the parents still (partially) providing for them. Similarly, studies on two primate species, macaques (Macaca nemestrina) and chimpanzees, revealed that individuals of these species started to follow the look-ups of human experimenters at the end of infancy97,98. Furthermore, our results are also in line with recent studies on other corvid species linking object permanence abilities to general development. For instance, Pollok and colleagues67 showed that magpies master Piagetian Stages 4 and 5 before nutritional independence. Hoffmann and colleagues99 investigated whether object permanence abilities are a function of the duration of development across four corvid species. Taking the hatching-to-fledging time as an indicator for development, they showed that Eurasian jays needed by far the shortest time for passing Stage 5 (6 weeks of age) and Stage 6 (7 weeks of age), with carrion crows (Stage 5: 11 weeks of age; Stage 6: 13 weeks of age) and ravens (Stage 5: 11 weeks of age; Stage 6: 14 weeks of age) following several weeks later.

These results are in contrast to findings on individuals of two psittacine species (Cyanoramphus auriceps, Psittacus erithacus), which show considerably slower developmental paces and achieve Piagetian Stage 5 only after independence (between 19 weeks of age, respectively 18 weeks of age)67. The differences in developmental speed and the linkage to general developmental patterns may reflect a general difference in maturing executive functions and hence cognitive trajectories of corvids and parrots99. However, it may also be possible that rapid cognitive development has been selected for in food-storing species, which use memory to retrieve stored food and have a larger hippocampus relative to the rest of the telencephalon than do species that store little or no food14,59.

Since ravens’ survival and reproductive output relies heavily on successful cooperation and alliances40,47, the rapid pace of ravens’ cognitive toolkit in the physical and social domain may thus also represent a selective response to manoeuvring in a world characterized by the complex challenges of an ever-changing ecological environment and governed by highly cooperative motives46,47.

Comparison of cognitive performance of ravens and great apes

With the exception of spatial skills, the quantitative comparison of performance scores of our ravens and the great ape individuals showed considerable similarities across the two domains of physical and social cognition. These results are also in line with a recent study using the PCTB to test cognitive performance of two Old World monkey species with chimpanzees showing higher performance scores than macaques in tasks of spatial understanding and tool-use only18. Since ravens perform impressive flight acrobatics, rely heavily on caching and pilfering of food-stores40,47, and have been shown to master stage 6 of object permanence68, the relatively low performance scores in the Space scale are surprising. Similarly, a recent study using the PCTB to investigate and compare cognitive skills of four parrot species (Ara glaucogularis, Ara ambiguus, Primolius couloni, Psittacus erithacus) showed that the parrots’ performance was also relatively poor in the scale Space (but also across all other scales tested). Individuals were significantly above chance only in the object permanence (Ara glaucogularis, Primolius couloni, Psittacus erithacus), and the rotation task (Ara glaucogularis56. Hence, our findings may echo Köhler who noted that “the success of the intelligence tests in general will be more likely endangered by the person making the experiment than by the animal” (p 265100). Since, ravens’ and other corvids’ social life is highly competitive101, all aspects of their cognitive abilities have likely been shaped by the need to out-compete conspecifics in general. It thus may be possible that our ravens’ performance in the scale Space—but also all other physical cognitive scales—was overshadowed by a social component with the ravens perceiving the experimenter as a competitor for the food reward. These findings may add a new aspect to proposals suggesting to integrate a competitive component into experimental designs71,102.

In contrast to our ravens’ performance, however, the parrots tested by Krasheninnikova and colleagues56 performed at chance level across all three physical and all three social cognitive scales. These results are in stark contrast to previous findings on parrots’ remarkable cognitive capacities (see for reviews49,103). They also  emphasize Tinbergen’s notion that the same test for a different species may therefore not be the same test104. Furthermore, differences in test performance between individuals of the parrot and our study may also be due to differences in socialization such as hand-raising, habituation and training procedures, and social bond strength between the birds and the experimenters (see also77,105). For instance, the birds in the present study were tested by two highly familiar people who had also hand-raised them. In contrast, tests in the study of Krasheninnikova and colleagues56 had been conducted by ten familiar experimenters, which had not hand-raised them, and four unfamiliar assistants. Hence, future studies should investigate the impact of these factors on cognitive performance in more detail to minimize possible counterproductive effects. In addition, analyses of why species fail in certain tests in combination with informed accounts of their ecological and social validity will aid in getting a better understanding of whether distinct tasks are too easy or too difficult for a given species to be solved18,89,102.

Furthermore, it is certainly an issue that the test battery was constructed and administered by humans10, influencing cognitive performance of our ravens overall. For instance, Schloegl and colleagues77 investigated the ontogeny of gaze following in ravens by using observations of spontaneously occurring gaze following behaviour between conspecifics and controlled experiments involving human experimenters. They found that visual co-orientation with conspecifics emerged around eight weeks of age, while gaze following behaviour to human-given cues could only be observed seven weeks later. Schloegl and colleagues82 suggested that human models may not be capable of providing the same stimulus quality as a conspecific due to emphasizing different aspects for eliciting gaze following behaviour. In contrast, Heinrich47 suggested that there is something unique about ravens that permits an uncanny closeness to develop with humans, thereby allowing insights in skills that could otherwise never be discovered.

Taken together, the present experiments provide evidence that our ravens’ experimental performance was on par with those of adult great apes in the similar tasks. They thus strengthen the idea that ravens evolved a general and flexible neural system for higher cognition36,106 rather than being highly specialized in a few domains only107. Yet, we do not claim that the cognitive abilities of ravens and great apes are generally similar since similarity at the behavioural level does not need to reflect the same underlying cognitive mechanisms50. This may be particular true for complex cognitive abilities such as tool use, cooperation, or referential signalling that involve different cognitive building blocks36. For example, referential signalling may involve aspects of learning, memory, empathy, and theory of mind, but the degree to which each of the abilities are involved and has advanced may differ between species and taxonomic groups46,108,109. In addition, it may also be the case that the cognitive competencies in the items tested in the PCTB simply did not differ substantially18. Furthermore, proponents of situated cognition argue that cognition reaches beyond the brain and tackle the relation between cognitive processes, on the one hand, and their neuronal, bodily, and worldly basis, on the other (for a review see110). This means that choices made via non-homologous body parts—beaks (ravens), hands (great apes), and eyes (ravens) combining panoramic sight with excellent stereoscopic vision111—not only involve different effectors but also different processors possibly influencing cognitive processing and output.

In addition, we do not claim that the cognitive performance of our eight ravens can be generalized to the species as a whole and corvids in general. For instance, some random effects seem to have influenced task performance suggesting to pay special attention in future studies to personality, task-performance across age and thus ontogeny of test-subjects (see e.g.112). Hence, the present study may pave the way to future collaborative studies and data sharing across research labs encouraging a ManyBirds project (see for related efforts113,114). It may thus aid in 1) tackling one of the biggest obstacles in Animal Cognition research, to obtain sufficient sample sizes, and 2) improving and adapting distinct tasks of test-batteries to better implement and mimic the ecology of the respective model species (see also115,116). Therefore, future studies should expand the range of investigated skills in a given test-battery beyond social interactions with humans and foraging contexts, and situate the findings within a comparative evolutionary framework (see also95,96,116). Furthermore, we hope to inspire more research into the impact of ontogeny on cognitive performance, which, although constituting one of Tinbergen’s four why’s, is especially lagging behind in studies of Animal Cognition117,118.