Fearfulness: An important addition to the starter kit for distinctively human minds.

Grossmann's impressive article indicates that - along with attentional biases, expansion of domain-general processes of learning and memory, and other temperamental tweaks - heightened fearfulness is part of the genetic starter kit for distinctively human minds. The learned matching account of emotional contagion explains how heightened fearfulness could have promoted the development of caring and cooperation in our species.

Tradition and invention: The bifocal stance theory of cultural evolution.

Cultural evolution depends on both innovation (the creation of new cultural variants by accident or design) and high-fidelity transmission (which preserves our accumulated knowledge and allows the storage of normative conventions). What is required is an overarching theory encompassing both dimensions, specifying the psychological motivations and mechanisms involved. The bifocal stance theory (BST) of cultural evolution proposes that the co-existence of innovative change and stable tradition results from our ability to adopt different motivational stances flexibly during social learning and transmission. We argue that the ways in which instrumental and ritual stances are adopted in cultural transmission influence the nature and degree of copying fidelity and thus also patterns of cultural spread and stability at a population level over time. BST creates a unifying framework for interpreting the findings of otherwise seemingly disparate areas of enquiry, including social learning, cumulative culture, overimitation, and ritual performance. We discuss the implications of BST for competing by-product accounts which assume that faithful copying is merely a side-effect of instrumental learning and action parsing. We also set out a novel "cultural action framework" bringing to light aspects of social learning that have been relatively neglected by behavioural ecologists and evolutionary psychologists and establishing a roadmap for future research on this topic. The BST framework sheds new light on the cognitive underpinnings of cumulative cultural change, selection, and spread within an encompassing evolutionary framework.

Bifocal stance theory: An effort to broaden, extend, and clarify.

The bifocal stance theory (BST) of cultural evolution has prompted a wide-ranging discussion with broadly three aims: to apply the theory to novel contexts; to extend the conceptual framework; to offer critical feedback on various aspects of the theory. We first discuss BST's relevance to the diverse range of topics which emerged from the commentaries, followed by a consideration of how our framework can be supplemented by and compared to other theories. Lastly, the criticisms that were raised by a subset of commentaries allow us to clarify parts of our theory.

Cognition blindness and cognitive gadgets.

Responding to commentaries from psychologists, neuroscientists, philosophers, and anthropologists, I clarify a central purpose of Cognitive Gadgets - to overcome "cognition blindness" in research on human evolution. I defend this purpose against Brunerian, extended mind, and niche construction critiques of computationalism - that is, views prioritising meaning over information, or asserting that behaviour and objects can be intrinsic parts of a thinking process. I argue that empirical evidence from cognitive science is needed to locate distinctively human cognitive mechanisms on the continuum between gadgets and instincts. Focussing on that requirement, I also address specific challenges, and applaud extensions and refinements, of the evidence surveyed in my book. It has been said that "a writer's idea of sound criticism is ten thousand words of closely reasoned adulation." I cannot disagree with this untraceable wag, but the 30 commentators on Cognitive Gadgets provided some 30,000 words of criticism that are of much greater scientific value than adulation. I am grateful to them all. The response that follows is V-shaped. It starts with the broadest conceptual and methodological issues and funnels down to matters arising from specific empirical studies.

When does social learning become cultural learning?

Developmental research on selective social learning, or 'social learning strategies', is currently a rich source of information about when children copy behaviour, and who they prefer to copy. It also has the potential to tell us when and how human social learning becomes cultural learning; i.e. mediated by psychological mechanisms that are specialized, genetically or culturally, to promote cultural inheritance. However, this review article argues that, to realize its potential, research on the development of selective social learning needs more clearly to distinguish functional from mechanistic explanation; to achieve integration with research on attention and learning in adult humans and 'dumb' animals; and to recognize that psychological mechanisms can be specialized, not only by genetic evolution, but also by associative learning and cultural evolution.

Rattling the cage and opening the door.

I share with Poulin-Dubois and with Sabbagh, Koenig and Kuhlmeier the conviction that more research is needed on the mechanisms supporting selective social learning in infants and children. However, my plea is more specific: for research that tests domain-specific hypotheses about mechanism against domain-general hypotheses derived from other fields of cognitive science. Many, but not all, of these alternative hypotheses relate to domain-general mechanisms of attention.

Avatars and arrows in the brain.

In this Commentary article we critically assess the claims made by Schurz, Kronbichler, Weissengrubler, Surtees, Samson and Perner (2015) relating to the neural processes underlying theory of mind and visual perspective taking. They attempt to integrate research findings in these two areas of social neuroscience using a perspective taking task contrasting mentalistic agents ('avatars'), with non-mentalistic control stimuli ('arrows'), during functional Magnetic Resonance Imaging. We support this endeavour whole-heartedly, agreeing that the integration of findings in these areas has been neglected in research on the social brain. However, we cannot find among the behavioural or neuroimaging data presented by Schurz et al. evidence supporting their claim of 'implicit mentalizing'-the automatic ascription of mental states to another representing what they can see. Indeed, we suggest that neuroimaging methods may be ill-suited to address the existence of implicit mentalizing, and suggest that approaches utilizing neurostimulation methods are likely to be more successful.

Players of Matching Pennies automatically imitate opponents' gestures against strong incentives.

There is a large body of evidence of apparently spontaneous mimicry in humans. This phenomenon has been described as "automatic imitation" and attributed to a mirror neuron system, but there is little direct evidence that it is involuntary rather than intentional. Cook et al. supplied the first such evidence in a unique strategic game design that gave all subjects a pecuniary incentive to avoid imitation [Cook R, Bird G, Lünser G, Huck S, Heyes C (2012) Proc Biol Sci 279(1729):780-786]. Subjects played Rock-Paper-Scissors repeatedly in matches between fixed pairs, sometimes with one and sometimes with both subjects blindfolded. The frequency of draws in the blind-blind condition was at chance, but in the blind-sighted condition it was significantly higher, suggesting automatic imitation had occurred. Automatic imitation would raise novel issues concerning how strategic interactions are modeled in game theory and social science; however, inferring automatic imitation requires significant incentives to avoid it, and subjects' incentives were less than 3 US cents per 60-game match. We replaced Cook et al.'s Rock-Paper-Scissors with a Matching Pennies game, which allows far stronger incentives to avoid imitation for some subjects, with equally strong incentives to imitate for others. Our results are important in providing evidence of automatic imitation against significant incentives. That some of our subjects had incentives to imitate also enables us clearly to distinguish intentional responding from automatic imitation, and we find evidence that both occur. Thus, our results strongly confirm the occurrence of automatic imitation, and illuminate the way that automatic and intentional processes interact in a strategic context.

Not-so-social learning strategies.

Social learning strategies (SLSs) are rules specifying the conditions in which it would be adaptive for animals to copy the behaviour of others rather than to persist with a previously established behaviour or to acquire a new behaviour through asocial learning. In behavioural ecology, cultural evolutionary theory and economics, SLSs are studied using a 'phenotypic gambit'-from a purely functional perspective, without reference to their underlying psychological mechanisms. However, SLSs are described in these fields as if they were implemented by complex, domain-specific, genetically inherited mechanisms of decision-making. In this article, we suggest that it is time to begin investigating the psychology of SLSs, and we initiate this process by examining recent experimental work relating to three groups of strategies: copy when alternative unsuccessful, copy when model successful and copy the majority. In each case, we argue that the reported behaviour could have been mediated by domain-general and taxonomically general psychological mechanisms; specifically, by mechanisms, identified through conditioning experiments, that make associative learning selective. We also suggest experimental manipulations that could be used in future research to resolve more fully the question whether, in non-human animals, SLSs are mediated by domain-general or domain-specific psychological mechanisms.

Baby steps: investigating the development of perceptual-motor couplings in infancy.

There are cells in our motor cortex that fire both when we perform and when we observe similar actions. It has been suggested that these perceptual-motor couplings in the brain develop through associative learning during correlated sensorimotor experience. Although studies with adult participants have provided support for this hypothesis, there is no direct evidence that associative learning also underlies the initial formation of perceptual-motor couplings in the developing brain. With the present study we addressed this question by manipulating infants' opportunities to associate the visual and motor representation of a novel action, and by investigating how this influenced their sensorimotor cortex activation when they observed this action performed by others. Pre-walking 7-9-month-old infants performed stepping movements on an infant treadmill while they either observed their own real-time leg movements (Contingent group) or the previously recorded leg movements of another infant (Non-contingent control group). Infants in a second control group did not perform any steps and only received visual experience with the stepping actions. Before and after the training period we measured infants' sensorimotor alpha suppression, as an index of sensorimotor cortex activation, while they watched videos of other infants' stepping actions. While we did not find greater sensorimotor alpha suppression following training in the Contingent group as a whole, we nevertheless found that the strength of the visuomotor contingency experienced during training predicted the amount of sensorimotor alpha suppression at post-test in this group. We did not find any effects of motor experience alone. These results suggest that the development of perceptual-motor couplings in the infant brain is likely to be supported by associative learning during correlated visuomotor experience.

False belief in infancy: a fresh look.

Can infants appreciate that others have false beliefs? Do they have a theory of mind? In this article I provide a detailed review of more than 20 experiments that have addressed these questions, and offered an affirmative answer, using nonverbal 'violation of expectation' and 'anticipatory looking' procedures. Although many of these experiments are both elegant and ingenious, I argue that their results can be explained by the operation of domain-general processes and in terms of 'low-level novelty'. This hypothesis suggests that the infants' looking behaviour is a function of the degree to which the observed (perceptual novelty) and remembered or expected (imaginal novelty) low-level properties of the test stimuli - their colours, shapes and movements - are novel with respect to events encoded by the infants earlier in the experiment. If the low-level novelty hypothesis is correct, research on false belief in infancy currently falls short of demonstrating that infants have even an implicit theory of mind. However, I suggest that the use of two experimental strategies - inanimate control procedures, and self-informed belief induction - could be used in combination with existing methods to bring us much closer to understanding the evolutionary and developmental origins of theory of mind.

Authors' response: mirror neurons: tests and testability.

Commentators have tended to focus on the conceptual framework of our article, the contrast between genetic and associative accounts of mirror neurons, and to challenge it with additional possibilities rather than empirical data. This makes the empirically focused comments especially valuable. The mirror neuron debate is replete with ideas; what it needs now are system-level theories and careful experiments ­ tests and testability.

Mirror neurons: from origin to function.

This article argues that mirror neurons originate in sensorimotor associative learning and therefore a new approach is needed to investigate their functions. Mirror neurons were discovered about 20 years ago in the monkey brain, and there is now evidence that they are also present in the human brain. The intriguing feature of many mirror neurons is that they fire not only when the animal is performing an action, such as grasping an object using a power grip, but also when the animal passively observes a similar action performed by another agent. It is widely believed that mirror neurons are a genetic adaptation for action understanding; that they were designed by evolution to fulfill a specific socio-cognitive function. In contrast, we argue that mirror neurons are forged by domain-general processes of associative learning in the course of individual development, and, although they may have psychological functions, they do not necessarily have a specific evolutionary purpose or adaptive function. The evidence supporting this view shows that (1) mirror neurons do not consistently encode action "goals"; (2) the contingency- and context-sensitive nature of associative learning explains the full range of mirror neuron properties; (3) human infants receive enough sensorimotor experience to support associative learning of mirror neurons ("wealth of the stimulus"); and (4) mirror neurons can be changed in radical ways by sensorimotor training. The associative account implies that reliable information about the function of mirror neurons can be obtained only by research based on developmental history, system-level theory, and careful experimentation.

Rethinking Norm Psychology.

Norms permeate human life. Most of people's activities can be characterized by rules about what is appropriate, allowed, required, or forbidden-rules that are crucial in making people hyper-cooperative animals. In this article, I examine the current cognitive-evolutionary account of "norm psychology" and propose an alternative that is better supported by evidence and better placed to promote interdisciplinary dialogue. The incumbent theory focuses on rules and claims that humans genetically inherit cognitive and motivational mechanisms specialized for processing these rules. The cultural-evolutionary alternative defines normativity in relation to behavior-compliance, enforcement, and commentary-and suggests that it depends on implicit and explicit processes. The implicit processes are genetically inherited and domain-general; rather than being specialized for normativity, they do many jobs in many species. The explicit processes are culturally inherited and domain-specific; they are constructed from mentalizing and reasoning by social interaction in childhood. The cultural-evolutionary, or "cognitive gadget," perspective suggests that people alive today-parents, educators, elders, politicians, lawyers-have more responsibility for sustaining normativity than the nativist view implies. People's actions not only shape and transmit the rules, but they also create in each new generation mental processes that can grasp the rules and put them into action.

Facial self-imitation: objective measurement reveals no improvement without visual feedback.

Imitation of facial gestures requires the cognitive system to equate the seen-but-unfelt with the felt-but-unseen. Rival accounts propose that this "correspondence problem" is solved either by an innate supramodal mechanism (the active intermodal-mapping, or AIM, model) or by learned, direct links between the corresponding visual and proprioceptive representations of actions (the associative sequence-learning, or ASL, model). Two experiments tested these alternative models using a new technology that permits, for the first time, the automated objective measurement of imitative accuracy. Euclidean distances, measured in image-derived principal component space, were used to quantify the accuracy of adult participants' attempts to replicate their own facial expressions before, during, and after training. Results supported the ASL model. In Experiment 1, participants reliant solely on proprioceptive feedback got progressively worse at self-imitation. In Experiment 2, participants who received visual feedback that did not match their execution of facial gestures also failed to improve. However, in both experiments, groups that received visual feedback contingent on their execution of facial gestures showed progressive improvement.

The cultural evolution of teaching.

Teaching is an important process of cultural transmission. Some have argued that human teaching is a cognitive instinct - a form of 'natural cognition' centred on mindreading, shaped by genetic evolution for the education of juveniles, and with a normative developmental trajectory driven by the unfolding of a genetically inherited predisposition to teach. Here, we argue instead that human teaching is a culturally evolved trait that exhibits characteristics of a cognitive gadget. Children learn to teach by participating in teaching interactions with socialising agents, which shape their own teaching practices. This process hijacks psychological mechanisms involved in prosociality and a range of domain-general cognitive abilities, such as reinforcement learning and executive function, but not a suite of cognitive adaptations specifically for teaching. Four lines of evidence converge on this hypothesis. The first, based on psychological experiments in industrialised societies, indicates that domain-general cognitive processes are important for teaching. The second and third lines, based on naturalistic and experimental research in small-scale societies, indicate marked cross-cultural variation in mature teaching practice and in the ontogeny of teaching among children. The fourth line indicates that teaching has been subject to cumulative cultural evolution, i.e. the gradual accumulation of functional changes across generations.

Social overshadowing: Revisiting cue-competition in social interactions.

In a large variety of contexts, it is essential to use the available information to extract patterns and behave accordingly. When it comes to social interactions for instance, the information gathered about interaction partners across multiple encounters (e.g., trustworthiness) is crucial in guiding one's own behavior (e.g., approach the trustworthy and avoid the untrustworthy), a process akin to trial-by-trial learning. Building on associative learning and social cognition literatures, the present research adopts a domain-general approach to learning and explores whether the principles underlying associative learning also govern learning in social contexts. In particular, we examined whether overshadowing, a well-established cue-competition phenomenon, impacts learning of the cooperative behaviors of unfamiliar interaction partners. Across three experiments using an adaptation of the iterated Trust Game, we consistently observed a 'social overshadowing' effect, that is, a better learning about the cooperative tendencies of partners presented alone compared to those presented in a pair. This robust effect was not modulated by gender stereotypes or beliefs about the internal communication dynamics within a pair of partners. Drawing on these results, we argue that examining domain-general learning processes in social contexts is a useful approach to understanding human social cognition.

Mnemicity: A Cognitive Gadget?

Episodic representations can be entertained either as "remembered" or "imagined"-as outcomes of experience or as simulations of such experience. Here, we argue that this feature is the product of a dedicated cognitive function: the metacognitive capacity to determine the mnemicity of mental event simulations. We argue that mnemicity attribution should be distinguished from other metacognitive operations (such as reality monitoring) and propose that this attribution is a "cognitive gadget"-a distinctively human ability made possible by cultural learning. Cultural learning is a type of social learning in which traits are inherited through social interaction. In the case of mnemicity, one culturally learns to discriminate metacognitive "feelings of remembering" from other perceptual, emotional, action-related, and metacognitive feelings; to interpret feelings of remembering as indicators of memory rather than imagination; and to broadcast the interpreted feelings in culture- and context-specific ways, such as "I was there" or "I witnessed it myself." We review evidence from the literature on memory development and scaffolding, metacognitive learning and teaching, as well as cross-cultural psychology in support of this view before pointing out various open questions about the nature and development of mnemicity highlighted by our account.

Self-recognition of avatar motion: how do I know it's me?

When motion is isolated from form cues and viewed from third-person perspectives, individuals are able to recognize their own whole body movements better than those of friends. Because we rarely see our own bodies in motion from third-person viewpoints, this self-recognition advantage may indicate a contribution to perception from the motor system. Our first experiment provides evidence that recognition of self-produced and friends' motion dissociate, with only the latter showing sensitivity to orientation. Through the use of selectively disrupted avatar motion, our second experiment shows that self-recognition of facial motion is mediated by knowledge of the local temporal characteristics of one's own actions. Specifically, inverted self-recognition was unaffected by disruption of feature configurations and trajectories, but eliminated by temporal distortion. While actors lack third-person visual experience of their actions, they have a lifetime of proprioceptive, somatosensory, vestibular and first-person-visual experience. These sources of contingent feedback may provide actors with knowledge about the temporal properties of their actions, potentially supporting recognition of characteristic rhythmic variation when viewing self-produced motion. In contrast, the ability to recognize the motion signatures of familiar others may be dependent on configural topographic cues.

Automatic imitation in a strategic context: players of rock-paper-scissors imitate opponents' gestures.

A compelling body of evidence indicates that observing a task-irrelevant action makes the execution of that action more likely. However, it remains unclear whether this 'automatic imitation' effect is indeed automatic or whether the imitative action is voluntary. The present study tested the automaticity of automatic imitation by asking whether it occurs in a strategic context where it reduces payoffs. Participants were required to play rock-paper-scissors, with the aim of achieving as many wins as possible, while either one or both players were blindfolded. While the frequency of draws in the blind-blind condition was precisely that expected at chance, the frequency of draws in the blind-sighted condition was significantly elevated. Specifically, the execution of either a rock or scissors gesture by the blind player was predictive of an imitative response by the sighted player. That automatic imitation emerges in a context where imitation reduces payoffs accords with its 'automatic' description, and implies that these effects are more akin to involuntary than to voluntary actions. These data represent the first evidence of automatic imitation in a strategic context, and challenge the abstraction from physical aspects of social interaction typical in economic and game theory.