Center for Behavior, Evolution, and Culture - Speaker Series

Human brains are much larger than one would expect for primates of our body size. They also feature more neurons and a proportionately larger neocortex. Prefrontal cortex, in particular, is significantly larger in humans than in other species. Although these features make the human brain unique, most of them are in line with allometric expectations, meaning that they can be predicted from the large size of our brains. Thus, human brains are fairly typical primate brains; they just became unusually large. Nonetheless, there are good reasons to believe that the evolutionary expansion of the human brain, especially of prefrontal cortex, caused evolutionary changes in neural connectivity and function. Dr. Striedter will review some of the evidence supporting this idea and place it in the larger context of brain and behavioral evolution.

Audio only. No video. There is evidence that humans have adaptations to avoid outgroup members who potentially harbor novel pathogens. However, intergroup contact can produce fitness costs (e.g., violence and disease), or benefits (e.g., trade, mates, and technologies), which suggests that it would be beneficial to possess an adaptation that enables the accurate tracking of group memberships. We predicted that accurate group tracking is accomplished through cognitively differentiating between social groups, and that this differentiation would be calibrated to the potential risk of infection. Consistent with this hypothesis, we found that increases in pathogen disgust are associated with increases in perceived similarity to ingroup-accented speakers and perceived dissimilarity from outgroup-accented speakers, particularly after exposure to pathogenic stimuli. Further, the effect of pathogen disgust on the accuracy of social categorization was mediated by intergroup differentiation. In this talk I present evidence for this group tracking hypothesis for accents, as well as recent evidence that extends the hypothesis to perceptions of similarity to religious groups, and to female judgments of the sexual attractiveness of ingroup- over outgroup-accented male speakers.

Human brains are much larger than one would expect for primates of our body size. They also feature more neurons and a proportionately larger neocortex. Prefrontal cortex, in particular, is significantly larger in humans than in other species. Although these features make the human brain unique, most of them are in line with allometric expectations, meaning that they can be predicted from the large size of our brains. Thus, human brains are fairly typical primate brains; they just became unusually large. Nonetheless, there are good reasons to believe that the evolutionary expansion of the human brain, especially of prefrontal cortex, caused evolutionary changes in neural connectivity and function. Dr. Striedter will review some of the evidence supporting this idea and place it in the larger context of brain and behavioral evolution.

Social relationships are a source of support and comfort in our lives, as well as a source of stress and conflict. Thus, the ability to regulate responses to both positive and negative emotions and cognitions arising from social interactions can significantly influence both physical and mental health. In my talk, I will present evidence from two studies suggesting an early-emerging and persistent role of the oxytocin system in sensitivity to social support. Specifically, common variants of the oxytocin receptor gene (OXTR) predict physiological, psychological, and behavioral responses to social support and stress in both adults and infants. I will also present results from a third study exploring the role of the oxytocin system in human social approach behavior. In addition, I will discuss my ongoing research on how internal working models of relationships (e.g. perceptions and beliefs about the status and intentions of social partners) interact with neuroendocrine activity to influence responses to social stress and interpersonal conflict.

Time, a fundamental aspect of human experience, is elusive and abstract. We cannot perceive time directly through the senses in the way we perceive color, texture, or heat. In order to make sense of, and talk about, temporal experience we must construe it in a stable and tractable manner. This is achieved via cultural practices built on the recruitment of bodily-grounded mechanisms that make human imagination possible, such as conceptual mappings. This remarkable but ubiquitous phenomenon manifests itself via ordinary linguistic metaphors as in the English expressions "the week ahead looks great" and "way back, in my childhood." Furthermore, beyond words and grammar, this phenomenon can be observed also through largely unconscious motor actions co-produced with speech — spontaneous gestures, which reveal its deep conceptual nature. But, is the human conceptualization of time universal? Based on shared general features of body morphology there is a widespread egocentric pattern which places future in front of Ego and past behind, as in the above linguistic examples. However, there are striking variations as well, which can be documented with rigorous ethnographic linguistic/behavioral observations. In this presentation I will show data from our projects conducted among the Aymara of the Andes, and the Yupno of the mountains of Papua New Guinea. The Aymara operate with a "reversed" egocentric pattern in which the future is conceived as being behind Ego and the past as being in front. More recently, and perhaps even more strikingly, we found that the Yupno spontaneously construe time spatially not even in egocentric terms, but in terms of allocentric topography: past as downhill and future as uphill — a pattern that had not been documented before. Moreover, the Yupno construal is not linear, but exhibits a particular "bent" geometry that appears to reflect the local terrain. Our results show that humans make sense of time sharing some basic spatial universals, but that striking differences also exist regarding the types of spatial properties that are recruited for spatializing time. The findings shed light on how, our universal human embodiment notwithstanding, linguistic, cultural, and environmental pressures generate and come to shape abstract concepts.

A core psychological motivation for people is to view themselves positively, yet for decades the vast majority of evidence for this motivation came from North American samples. More recent research finds that this motivation varies importantly across cultures, because there are different kinds of positive views that are prioritized in different cultures. Positive self-views are primarily made manifest in North America through a desire to maintain high self-esteem – that is, a desire to have a positive evaluation of themselves. In contrast, the kind of positive self-view that is prioritized in several East Asian cultures is a strong desire to maintain face – that is, a desire to have others in one’s social network judge that the individual is functioning adequately in their position within that network. These two distinct kinds of positive self-views are associated with highly divergent psychological processes. In their efforts to maintain high self-esteem, North Americans demonstrate stronger tendencies for self-enhancement, they show more of a promotion focus, maintain a largely internal frame of awareness, and have more entity theories of abilities. In contrast, in their efforts to maintain face, East Asians show stronger tendencies for self-improvement, demonstrate more of a prevention focus, maintain a largely external frame of awareness, and have more incremental theories of abilities. Evidence for cultural variation in each of these processes will be discussed, alongside discussions of alternative explanations.

A core psychological motivation for people is to view themselves positively, yet for decades the vast majority of evidence for this motivation came from North American samples. More recent research finds that this motivation varies importantly across cultures, because there are different kinds of positive views that are prioritized in different cultures. Positive self-views are primarily made manifest in North America through a desire to maintain high self-esteem – that is, a desire to have a positive evaluation of themselves. In contrast, the kind of positive self-view that is prioritized in several East Asian cultures is a strong desire to maintain face – that is, a desire to have others in one’s social network judge that the individual is functioning adequately in their position within that network. These two distinct kinds of positive self-views are associated with highly divergent psychological processes. In their efforts to maintain high self-esteem, North Americans demonstrate stronger tendencies for self-enhancement, they show more of a promotion focus, maintain a largely internal frame of awareness, and have more entity theories of abilities. In contrast, in their efforts to maintain face, East Asians show stronger tendencies for self-improvement, demonstrate more of a prevention focus, maintain a largely external frame of awareness, and have more incremental theories of abilities. Evidence for cultural variation in each of these processes will be discussed, alongside discussions of alternative explanations.

Social relationships are a source of support and comfort in our lives, as well as a source of stress and conflict. Thus, the ability to regulate responses to both positive and negative emotions and cognitions arising from social interactions can significantly influence both physical and mental health. In my talk, I will present evidence from two studies suggesting an early-emerging and persistent role of the oxytocin system in sensitivity to social support. Specifically, common variants of the oxytocin receptor gene (OXTR) predict physiological, psychological, and behavioral responses to social support and stress in both adults and infants. I will also present results from a third study exploring the role of the oxytocin system in human social approach behavior. In addition, I will discuss my ongoing research on how internal working models of relationships (e.g. perceptions and beliefs about the status and intentions of social partners) interact with neuroendocrine activity to influence responses to social stress and interpersonal conflict.

Being lied to, cheated upon, stolen from—these are among life’s most emotional experiences, and even watching them happen to someone else can trigger strong feelings. Recent work has confirmed the important role of emotion in human morality, but less is known about precisely which emotions are involved and how emotion exerts its influence. In this talk, I discuss the role of distinct emotions in morality, with a focus on disgust. I also describe a new line of research that aims to examine how emotion and cognition interact to give moral values their special weight in decision-making. Taken together, these two lines of work suggest that both emotion and cognition are key contributors to human morality.

Being lied to, cheated upon, stolen from—these are among life’s most emotional experiences, and even watching them happen to someone else can trigger strong feelings. Recent work has confirmed the important role of emotion in human morality, but less is known about precisely which emotions are involved and how emotion exerts its influence. In this talk, I discuss the role of distinct emotions in morality, with a focus on disgust. I also describe a new line of research that aims to examine how emotion and cognition interact to give moral values their special weight in decision-making. Taken together, these two lines of work suggest that both emotion and cognition are key contributors to human morality.

The capacity of organisms to deal with evolutionary novelty has been regarded by some as a puzzle. If adaptations have been shaped by natural selection operating in the past, then how can they possibly respond adaptively to objects, events, and situations that clearly did not exist until recently? This has been regarded as particularly problematic for adaptationist accounts of human behavior because we are clearly surrounded by many evolutionary novelties, from football to Facebook, that do not cause our brains to seize up in a failure to compute. Traditionally, the answer has been that humans are equipped with more or better general-purpose cognitive capacities than are other animals, though mounting comparative evidence suggests that it is not primarily in the most general mechanisms of cognition that humans and other primates differ. Arguably, progress on the novelty puzzle has been impeded by the lack of adequate theory regarding how adaptations, and in particular psychological adaptations, might be expected to respond to evolutionary novelty. In this talk I describe elements of what such a theory might look like, drawing on prior work in biology, evolutionary psychology, culture-gene coevolution theory, and Bayesian models of cognition, and illustrating the ideas with examples from recent research.

The capacity of organisms to deal with evolutionary novelty has been regarded by some as a puzzle. If adaptations have been shaped by natural selection operating in the past, then how can they possibly respond adaptively to objects, events, and situations that clearly did not exist until recently? This has been regarded as particularly problematic for adaptationist accounts of human behavior because we are clearly surrounded by many evolutionary novelties, from football to Facebook, that do not cause our brains to seize up in a failure to compute. Traditionally, the answer has been that humans are equipped with more or better general-purpose cognitive capacities than are other animals, though mounting comparative evidence suggests that it is not primarily in the most general mechanisms of cognition that humans and other primates differ. Arguably, progress on the novelty puzzle has been impeded by the lack of adequate theory regarding how adaptations, and in particular psychological adaptations, might be expected to respond to evolutionary novelty. In this talk I describe elements of what such a theory might look like, drawing on prior work in biology, evolutionary psychology, culture-gene coevolution theory, and Bayesian models of cognition, and illustrating the ideas with examples from recent research.