In this short, dense book Heyes introduces cultural evolutionary psychology, which seeks to combine cognitive psychology with cultural evolution. She posits that human cognitive traits, which were previously assumed to be genetic, might, instead, be passed on through cultural evolution. Heyes subscribes to the selectionist approach of Donald Campbell, where what is required for evolution to occur is “(1) mechanisms for introducing variation; (2) consistent selection processes; and (3) mechanisms for preserving and/or propagating the selected variations.” Of course, these mechanisms can operate culturally as well as genetically.
Heyes suggests that humans have genetically inherited three basic traits that have helped with domain-general learning. First, by temperament humans are extremely social primates, which has facilitated coordination amongst large groups and learning through others. Second, humans have “genetically inherited attentional biases [that] ensure that the attention of human infants is locked-on to other agents from birth.” This includes a propensity to look at the faces of others and gaze-cuing, where attention is focused on the object of another’s attentional gaze. Therefore, “the flow of information that infants receive about the world is guided by adults’ knowledge of what is important and interesting.” Familiar voices, such as the mother’s, as well as native language speech in general, also attract inordinate attention in infants. Finally, humans have inherited powerful information processors, which are domain-general. The human pre-frontal cortex is proportionally larger than in the brain of any other primate. Associative learning techniques and cascading effects allow humans to process ever-more information, while human’s large memory allows for exceptional retention. In addition, executive function, consisting of inhibitory control, working memory, and cognitive flexibility, allows humans to develop such facilities as reasoning, problem solving, and planning. “Cognitive mechanisms that we have reason to believe are distinctively human…. include: (1) mechanisms that are specialized for dealing with the inanimate world, such as causal understanding; (2) faculties that are equally likely to process animate (social) and inanimate (asocial) events, such as episodic memory; and (3) various forms of cognition specialized for dealing with social stimuli, such as face processing, imitation, and mindreading.”
Heyes makes the case that “most social learning- perhaps all non-cultural social learning- depends on the same learning mechanisms as asocial learning, and that these are broadly associative processes that encode information for long-term storage by forging excitatory and inhibitory links between event representations.” What makes humans unique, however, is selective social learning. This is explicit metacognition techniques that “focus social learning on knowledgeable agents so precisely that they encourage high-fidelity copying of behavior. Because it is exclusive, specific, and accurate, this kind of copying promotes cultural evolution by enhancing “parent-offspring relations”…. Explicitly metacognitive rules are typically learned through social interaction and, therefore, show marked cross-cultural variation.” Most importantly, “metacognitive social learning strategies are learned from others (emphasis mine).” In contrast, “the behavior of nonhuman animals and young children can be described and predicted by formulae such as copy the successful or copy older individuals, but the strategies or rules are in the minds of scientific observers, not the actors themselves.” By adulthood, humans are unique in explicitly choosing successful prototypes to mimic. This selective social learning is then passed down and retained only as it is useful. The ability to selectively copy is culturally learned.
According to Heyes, a second cognitive gadget, passed down through cultural evolution, is imitation. This formation solves Andrew Meltzoff’s correspondence problem, where he asks how can cognition “connect the felt but unseen movements of the self with the seen but unfelt movements of the other?” Heyes suggests, “the link between the sensory and motor representations is bidirectional and excitatory…. Matching vertical associations are forged by learning, predominantly social learning, they are not inborn or genetically inherited.” Vertical associations are formed through “correlated sensorimotor experience: experience in which seeing and doing a particular action occur close together in time and in a predictive or “contingent” relationship.” Opaque perception is facilitated by cultural tools such as mirrors, video recordings, synchronized activities and rituals, such as dance, drills and games, action words that provide equivalence experience, and feedback through adults imitating infant behavior in a mirrored way. Heyes suggests that “the most important function of imitation [is] high fidelity cultural inheritance not of object-directed actions, but of communicative and gestural skills…. They include the sequences of body movements that enable group members to communicate without words and, thereby, to coordinate their activities when words are absent (for example, when the message is ineffable, and before language co-evolved), and when words are dangerous (for example, when a group is stalking prey). They also include the sequences of body movements, such as those involved in ritualistic dancing, that enable group members to bond- to achieve the states of trust and commitment required for cooperative action.” Finally, “identical twins are no more alike in their imitative ability than fraternal twins” suggesting that skill in imitation is not genetically inherited.
The third cognitive gadget Heyes brings up is theory of mind. She suggests that theory of mind was a necessary prerequisite for teaching, “acts with the intention of producing enduring change in the mental states- especially the knowledge states- of another agent.” Heyes suggests that theory of mind is not a concept that is inherited genetically, but that “children are taught about the mind by members of their social group, and the information that is culturally inherited in this way forms a conceptual structure enabling the ascription of mental states to the self and others.” Heyes continues, “mindreading involves the derivation of meaning from signs…. The signs are facial expressions, body movements, and utterances- many of them conventional- and their meaning relates to the actor’s mental states…. Novice mindreaders learn not only that behavior can be, but that it should be, produced by rational interactions among beliefs and desires, and they are encouraged to make their own behavior obey these conventions.” Many of these social beliefs are culturally specific and, therefore, cannot be inherited genetically.
The fourth cognitive gadget Heyes touches on is language. She admits that she is not an expert in this field, but she still ambivalently concludes that language acquisition is more culturally than genetically inherited. “The cognitive processes of language acquisition evolved genetically to fulfill nonlinguistic functions.” Domain-general tools that evolved genetically became culturally evolved to facilitate language, uniquely in humans. Heyes came to this conclusion through empirical studies which questioned a genetic Universal Grammar, first posited by Chomsky. Studies of the five to eight thousand languages spoken in the world today show that there is little universal linguistically be it phrase category, phrase structure, linear order, numerals, or even the basic concepts of nouns, verbs, adjectives, and adverbs. Some languages lack adverbs entirely, whereas others adopt a fifth major category, ideophones. Furthermore, fMRI studies have shown that neural activity is spread out across the brain during language processing, not focused in Broca’s area as Universal Grammar proponents had previously insisted. Computer simulations have also shown that complex grammatical construction can be acquired using domain-general tools. Other studies have taught adult humans “artificial grammar”, which uses arbitrary rules, effectively. Other studies have concluded that “Universal Grammar could not have evolved genetically because linguistic conventions change too quickly.” Rules of parsimony also suggest that domain-general processing should be sufficient to generate language acquisition in humans, through cultural evolutionary mechanisms alone.
Heyes concludes by defending the idea of group selection. She suggests that these cognitive gadgets, distinctly human cognitive mechanisms, all evolved through cultural evolution at the group level. These mechanisms increased fitness for individuals by improving their living conditions and increasing their likelihood of reproducing, but they also helped at the group level because “groups with better living conditions are more likely to persist through time and to bud, not only because their members are more likely to survive and reproduce, but also because these groups are more likely to attract net immigration. Groups with better living conditions are also more likely to have their practices emulated by other groups, including childrearing and ritual practices that foster the development of particular cognitive mechanisms.” These mechanisms are amplified through network effects that “go on between people, rather than inside individual’s heads- such as conversation, storytelling, turn-taking, collective reminiscing, teaching, demonstrating, and engaging in synchronous drills.” Inheritance of these cultural mechanisms can take place through many routes (vertical, oblique, or horizontal copying) and, therefore, the mechanisms become more robust over time. Also, redundancy of routes can amplify and solidify acquisition. Children “have many opportunities to pick up and consolidate the same information…. And this does not occur by chance, or as a consequence of a blind selection process.” Many of these specific mechanisms are locally, but not globally, optimal in their particulars. “Distinctively human cognitive mechanisms need to be nimble, capable of changing faster than genetic evolution allows.” With the growth of human group size, specialization allowed for expertise and, as new techniques emerged, they were more likely to be seen by others, imitated, and passed on to the next generation. “Cultural evolutionary psychology, the cognitive gadgets theory, suggests that distinctively human cognitive mechanisms are light on their feet, constantly changing to meet the demands of new social and physical environments.”
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