Center for Behavior, Evolution, and Culture

Wendy Saltzman - Endocrinology of Female Reproductive Competition in Cooperatively Breeding Marmoset Monkeys
2007-01-22 00:00 (America/Los_Angeles)
Wendy Saltzman: UC Riverside Department of BiologyCommon marmosets are cooperatively breeding monkeys that exhibit high female reproductive skew: typically only a single, dominant female breeds successfully in each social group. Laboratory studies have indicated that reproductive suppression in subordinate females is not aggressively imposed on them by dominant females and is not associated with stress; instead, it is mediated by a specific, presumably adaptive neuroendocrine mechanism. Moreover, subordinate females readily begin to breed under favorable conditions, such as following introduction of an unrelated male into the group, and show no impairments in their ability to maintain pregnancy or successfully produce offspring. When two females breed concurrently, however, they engage in overt reproductive competition, with pregnant females commonly killing one anotherâ€™s infants. In sum, our findings are consistent with recent manipulation-based models of reproductive skew, in which reproductive suppression in non-breeders is mediated, mechanistically, by self-restraint but has evolved in response to selection â€“ namely, infanticide â€“ imposed by breeding females.http://www.bec.ucla.edu/papers/Saltzman_1.22.07.pdf

Rob Boyd - Reciprocity is not sufficient to explain human cooperation
2007-01-08 00:00
Rob Boyd: UCLA Department of AnthropologyRecent discussions of human cooperation assume that the theory reciprocal altruism provides an established explanation for human cooperation, and that therefore, alternative explanations invoking cultural group selection face a burden of proof. In this talk, I argue that this assumption is not justified. The theory of reciprocal altruism does predict that cooperative behavior among small groups of unrelated individuals will evolve, but this theory is not supported by most empirical data. The theory of reciprocal altruism also predicts that cooperative behavior is evolutionarily stable, but also predicts that any other behavior is equally likely to be stable, and thus does not provide a sufficient explanation for the commonness of large scale human cooperation. I also argue that the theory of cultural group selection is cogent, and consistent with much empirical data.

Dario Maestripieri - Biological bases of caregiver attachment
2006-12-04 00:00
Dario Maestripieri: University of Chicago Department of Comparative Human DevelopmentIn human and nonhuman primates, caregiver attachment is a motivational/ behavioral system that promotes the maintenance of proximity between a caregiver and an infant and facilitates the expression of caregiving behavior. Comparative data on female interest in infant and infant-directed behavior in nonhuman primates and humans will be used to illustrate the proximate regulation, development, adaptive function, and evolution of the caregiver attachment system.

Peter Richerson - The Role of Religion in Human Cooperation: Experiments Using Economic Games
2006-11-27 00:00
Peter Richerson: UC Davis Department of Environmental Science and PolicyReligion is often held to play a large, even dominant, role in supporting human cooperation. Much variation in propensities to cooperate and treat others fairly exists within and between human societies. Previous work by social psychologists suggested that religion plays a small role in explaining this variation, but the validity of the dependent variables used is questionable. We used behavior in Dictator, Trust, and Public Goods games as dependent variables to test for the effects of a wide variety of measures of religious participation, experiences, beliefs, and affiliation on cooperation and other prosocial behaviors. Despite the data-dredging aspects of our experimental design, we found significant effects of religious variables on prosocial behavior. Further, various dimensions of religiosity correlated with game behavior in a way that is somewhat consistent with findings from the experiments devised by social psychologists. However, we found little evidence an “ingroup” effect; participants did not send more money to individuals with similar religious preferences. By comparing numerous models using an information-theoretical approach, we draw some general conclusions about which theories are data are most likely to support.

Joan Silk - The origins of prosocial preferences
2006-11-20 00:00
Joan Silk: UCLA Department of AnthropologyHumans differ from most other animals, and from virtually all other primates, in the extent of our dependence on cooperation. In humans, altruism seems to be at least partly based on empathy and genuine concern for the welfare of others (Batson and Powell 1998; Fehr and Fischbacher 2003). We may also be motivated by a concern for reputation (Haley and Fessler 2005), that makes us want others to think that we are generous, fair, or charitable. Nonhuman primates also act altruistically, but the extent and deployment of altruism in primate groups is much more limited than it is in human societies. Altruistic interactions usually involve very small numbers of individuals (usually dyads) and is strongly biased by kinship. There is some evidence for reciprocity among unrelated individuals, but these exchanges are generally restricted to short-term exchanges of low-cost commodities. It is not clear what limits altruism in nonhuman primate groups. New work suggests, however, that differences in the deployment of altruism in human and nonhuman primate may be linked to differences in the capacity for empathy, the existence of moral sentiments, and the concern for the welfare of others.

Michael Cannon - Modeling the Tradeoff between Foraging and Farming
2006-11-13 00:00
Michael Cannon: CSU Long Beach Department of AnthropologySome archaeologists have used a model of optimal time allocation from human behavioral ecology to help explain variability over space and time in the importance of farming vs. foraging. I discuss a model that builds on this previous work in an effort to enable a more detailed understanding of the factors relevant to the development of prehistoric agriculture. This model is more explicit about the activities involved in agriculture, modeling the costs and benefits of harvest-producing activities and post-harvest processing activities separately; this potentially provides a means for integrating labor division into the model. The model also enables a consideration of the roles that both mean productive efficiency and variability in production might play in the evolution of agricultural economies. Model predictions are evaluated against archaeological data from the American Southwest to clarify the factors that underlay increases in the importance of agriculture in this region.

Paul Bloom - Bodies and Souls
2006-11-06 00:00
Paul Bloom: Yale Department of PsychologyHow do we think about bodies and souls? Findings from developmental psychology suggest that both children and adults see physical entities such as objects (or bodies) as fundamentally distinct from psychological entities such as minds (or souls). We are natural-born dualists. Our dualism explains why we are so drawn to certain religious beliefs — such as life after death and the existence of supernatural entities — and it also underlies certain aspects of moral reasoning.

Mark Changizi - Letters from nature
2006-10-30 00:00
Mark Changizi: CalTech Sloan-Swartz Center for Theoretical NeurobiologyReading pervades every aspect of our daily lives, so much so that one would be hardpressed to find a room in a modern house without words written somewhere inside. Many of us now read more sentences in a day than we listen to. Not only are we highly competent readers, but our brains even appear to have regions devoted to recognizing words. A Martian just beginning to study us humans might be excused for concluding that we had evolved to read. But, of course, we havenâ€™t. Reading and writing is a recent human invention, going back only several thousand years, and much more recently for many parts of the world. We are reading using the eyes and brains of our illiterate ancestors. Why are we so good at such an unnatural act? Here I describe new evidence that, although we have not evolved to be good at reading, writing appears to have culturally evolved to be good for the eye. More specifically, new research supports the hypothesis that human visual signs look like nature, because that is what we have evolved over millions of years to be good at seeing. This ecological hypothesis for letter shape not only helps explain why we are such good readers, but answers the question, Why are letters and other visual signs shaped the way they are?http://www.bec.ucla.edu/papers/Changizi_10.30.06.pdf

Colin Camerer - Status, ethnicity, and wealth in Vietnam: Evidence from experimental games
2006-10-23 00:00
Colin Camerer: CalTech Department of Business EconomicsWe conducted economic experiments to investigate interethnic discrimination with the members of three ethnic groups, i.e., Vietnamese, Khmer and Chinese, in southern Vietnam. Vietnamese are the major ethnic group, and Khmer and Chinese are main minority groups. Chinese are the richest and Khmer are the poorest among the three ethnic groups.
We found that 1) Khmer (poor minority) show the strongest solidarity. 2) Vietnamese (majority) do not show solidarity when they are matched with Khmer (poor minority), but demonstrate ingroup bias when they are matched with Chinese (rich minority). 3) Vietnamese often comply with the social norm of fair allocations, choosing equal splits both in Dictator Game and Third Party Punishment Game. 4) Khmer send much more in Third party Punishment game than in Dictator Game, while Chinese reduce the amount sent when the third party is introduced (crowing-out effects). 4) Both minorities punish Vietnamese more severely when Vietnamese violate the norm. 5) Both minorities protect ingroup victims more than they do outgroup victims.

Andreas Wilke - The adaptive problem of finding resources
2006-10-16 00:00
Andreas Wilke: UCLA Department of AnthropologyWhen resources are distributed in patches animals must decide when to switch from a depleted patch. The optimal policy is given by the Marginal Value Theorem, which has successfully predicted animal behaviors, but as a mechanism it becomes problematic when each patch contains few discrete prey items. Biologists have proposed simple alternative decision mechanisms and calculated in which environments each works well. We tested whether the decision mechanisms evolved to direct animals when to leave a food patch also underlie human decision making in the same context, and whether humans in an internal-search task (e.g. information in memory) use the same mechanisms as in an external-search task (e.g. physical objects).

Wendy Treynor - Are the Most Mistrustful the Least Trustworthy? Studies of Unethical Behavior
2006-10-09 00:00
Wendy Treynor: USC Institute for Creative TechnologiesIs one who believes that unethical activity is common unlikely to act ethically? To test the hypothesis that cynical beliefs predict unethical behaviors, actual unethical activity was examined by developing two laboratory techniques. In the American History Aptitude Test cheating technique, participants were told they would be rewarded with 10 cents for each question on a test that â€œaccidentallyâ€ had the correct answers already marked on it, whereas in the Weight Perception Task stealing technique, participants estimated the weight of objects using coins from a bowl, which they sat alone with, containing $71.00 of coins. Regardless of technique used, cynicismâ€”the belief that
others are engaging in unethical acts or that unethical behavior is common or normalâ€”was found to positively predict unethical behavior.

Dacher Keltner - Evolution's Soul: What Laughter, Smiling, Lip Puckers, and Goosebumps Tell us About the Evolution of Human Goodness
2006-05-29 00:00
Dacher Keltner: UC Berkeley Department of PsychologyIn this talk I will present recent work on the pro-social emotions. I will present studies of smiling, the relations between oxytocin and the nonverbal displays of love and desire, and recent evidence exploring the role of vagus nerve activity in compassion and pro-social dispositions. I will use these data to offer the beginnings of a theory of the emotion-related origins of pro-sociality, drawing upon Darwin’s own speculations and those of recent philosophers and behavioral scientists.

Robert Hoffmann - Religion, Religiosity and Cooperation: An Experimental Study from Malaysia
2006-05-22 00:00
Robert Hoffmann: Department of Economics, Nottingham University Business School, The University of NottinghamHuntington’s notion of a clash of cultures has attracted a great deal of attention in recent years. In particular, religious differences as well as religious fundamentalism have been identified as crucial dimension of present culture clashes. We conducted a study to explore to what extent different religions and religiosity affect the economic interactions between individuals as a test of this notion. The study is based on religious attitude surveys and incentivised economic experiments with repeated prisoner’s dilemma play among Malaysian subjects. The multi-ethnic nature of Malaysia is ideally suited to match subjects for game play from the world’s major religions (Islam, Catholicism, Protestantism, Hinduism and Buddhism) while holding other socio-economic factors constant.

Bruce Winterhalder - Seven Reasons to Remain a Forager
2006-05-15 00:00
Bruce Winterhalder: UC Davis Department of AnthropologyArchaeological research shows that many human populations continued to hunt-and-gather for thousands of years after beginning the use of plant domesticates. This kind of mixed economy is rare in the ethnographic literature on foragers and horticulturalists; its persistence for millennia in the early stages of agricultural origins is inexplicable under much current theory. In this paper I describe models and concepts from evolutionary anthropology which may help us to explain this novel,persistent, prehistoric mode of production. The more important ones include (a) the population ecology of the domesticates themselves, (b) environmental fluctuation, (c) temporal discounting of subsistence options, (d) maintenance of technological knowledge in low-density populations, and (e) institutional mechanisms of risk-manage under changing economic regimes. Collectively these ideas are meant to demonstrate, contra Sahlins and substantivism, the utility of a selective set of micro-economic concepts in the study of pre-market economies.

Michael Shermer - Evonomics: Natural Selection, the Invisible Hand, and the New Science of Evolutionary Economics
2006-05-08 00:00
Michael Shermer: Skeptic MagazineThere are a number of parallels between evolution and economics that we shall explore on two tiersâ€”historical and theoretical: the parallels between natural selection and the invisible hand; the nature of evolution and the characteristics of a free market economy; the reluctance to accept the theory of evolution and free market economics; evolution and economics as emergent properties; how evolution shaped economic behavior; and contingency in evolution and path dependency in economies. In short, natural selection and the invisible hand are analogous descriptors for analogous phenomena.

Nancy Burley - Sexual Imprinting: New Approaches to an Old Problem
2006-05-01 00:00
Nancy Burley: UC Irvine Department of Ecology & Evolutionary BiologySexual imprinting, a process by which early contact with parents shapes the mate preferences of developing young, has been widely documented among birds and has been reported for other vertebrates, especially mammals (including humans). Historically, studies of imprinting have emphasized causal and ontogenetic perspectives, with function and evolutionary consequences receiving less attention. Recent quantitative models have investigated a possible role for sexual imprinting in vertebrate speciation processes, but little empirical support for this possibility has been provided. Moreover, recent studies suggest that sensory drive processes exert strong, unlearned influences on mate preferences which might override tendencies to imprint on novel traits that emerge in incipiently diverging populations. Here I report results of several experiments designed to evaluate the tendency of both sexes of zebra finches to imprint on novel traits of parents with otherwise normal phenotypes. The novel (experimental) traits are crests of various colors and patterns. Previous research (Burley & Symanski 1998) indicates that female zebra finches reared with wild-type (uncrested)parents have sensory biases favoring white-crested males; normally reared males lack this bias and favor uncrested females. By rearing young with crested parents, I investigated how sensory drive and imprinting processes interact. Results suggest that imprinting responses of both sexes may vary considerably with the perceived information content of experimentally manipulated traits, and that some evolutionarily novel traits may promote reproductive isolation in diverging populations.http://www.bec.ucla.edu/papers/Burley_5.1.06.pdf

Joseph Campos - On the Epigenesis of Fear in the Human Infant
2006-04-24 00:00
Joseph Campos: UC Berkeley Department of PsychologyThere is a fascinating paradox about fear of heights in humans and some animal species. Such fear has enormous biological adaptive value, represents a true life-span emotional reaction, and constitutes one of the strongest and most reliably-elicited fears in the human. As such, one would expect fear of heights to be innate, or under strong maturational control. Indeed, until recently, it was so considered. However, there is now no doubt that fear of heights develops as the result of experience, more specifically experiences linked to the onset of self-produced locomotion. It is not a maturational or innate event.
What creates fear of heights and how does locomotor experience play a role in its ontogeny? We can rule out three likely candidates as playing a causal role. Depth perception is well established before such fear develops; falling experiences are relatively rare; and maternal emotional signaling has little if any impact at the age of onset of locomotion. What, then, may be the process(es) by which such biologically-adaptive wariness comes about?
In this talk, evidence is presented for the role of a discrepancy between sensory systems in the ontogeny of these fears. The discrepancy we propose to be playing a causal role is related to the discrepancy that in adults makes heights â€œdizzying.â€ More specifically, one experiences height vertigo when information reaches the brain that the head and body is moving (even minutely so), but visual information discrepantly fails to confirm such self-movement. It turns out that infants have good vestibular and kinesthetic information about self-movement from early in life, but lack responsiveness to flow in the visual periphery until after the acquisition of locomotor experience. So, only after â€œvisual proprioceptionâ€ becomes functional is the infant capable of experiencing the discrepancy that produces height vertigo.
The talk will:
(a) Visually illustrate what visual proprioception is (it is not a phenomenon well-known to behavioral scientists),
(b) Provide evidence for the role of locomotor experience on visual proprioception, and
(c) Present results of two studies showing correlations between responsiveness to optic flow and the probability of showing wariness of heights in infants at two different ages.http://www.bec.ucla.edu/papers/Campos_24.4.06.doc

Chris Guzelian - Evolution, Selfish Lies, and Free Speech
2006-04-17 00:00
Chris Guzelian: Searle Scholar, Northwestern University School of LawEvidence increasingly suggests that selection between competing ideas to become a prevailing social belief may be strongly influenced by evolutionarily descended limitations on human sensory and mental capabilities. Scholars posit that these limitations permit many “selfish” ideas to gain social traction and spread epidemically, driving out and shutting out truth from collective understanding in the selection process. An evolutionary perspective, combined with settled principles of free speech law, indicates that the explicit combating of various selfish false ideas through technological, educational, legal, financial, or other means may be necessary to avoid self-sustaining mass delusions in a globalizing world.

Jeffrey Davis - Fisher's Sociological Imagination
2006-04-10 00:00
Jeffrey Davis: California State University Long Beach Department of SociologyFisher is widely known for his extraordinary contributions to population genetics and evolutionary biology. His sociological insights have received far less attention, even though five of the twelve chapters of The Genetical Theory of Natural Selection are devoted to developing a theory of the evolutionary consequences of human social organization. For my presentation, I will review Fisher’s sociology and the parameters of his model of social organization. I also offer some extensions to Fisher’s model. In conclusion, I contend that Fisher’s insights provide the basis of a rich theoretical research program in evolutionary sociology.

Peter Whybrow - American Mania: When More Is Not Enough
2006-04-03 00:00
Peter Whybrow: UCLA David Geffen School of MedicineDr. Whybrow poses the question, â€œAre we Americans becoming the first addicts of the technological age?â€ Despite an astonishing appetite for life, more and more Americans are feeling overworked and dissatisfied in the worldâ€™s most affluent nation, epidemic rates of stress, anxiety, depression, obesity, and time urgency are now grudgingly accepted as part of everyday existenceâ€”they signal the American Dream gone awry. Drawing upon economics, history, evolutionary psychology, and scientific case studies, Dr. Whybrow ground the extraordinary achievements and excessive consumption of the American nation in an understanding of the biology of human craving and the reward system of the brainâ€”offering a comprehensive physical explanation for the addictive mania of consumerism. Whybrow shows how human biology is ill equipped to cope with the demands of the 24/7, global, information-saturated, rapid-fire culture we not only have created but also have come to crave. Dr. Whybrow concludes with a discussion of how one may step back from this treadmill to live a healthful life. But he also offers a cautionary tale: As a society if we do not learn to curtail our cravings, we may be entering a self-destructive phase. Fundamental to change will be an objective evaluation of the laissez-faire market ideology and a reinvigoration of our role as citizens in this driven consumer culture.

Terrence Deacon - Devo-Devo: How Relaxed Selection Can Contribute To The Evolution And Self-Organization Of Complexity
2006-03-13 00:00
Terrence Deacon: UC Berkeley Department of AnthropologyAlthough biologists have long recognized examples of regressive processes in evolution as well as a role for regressive processes in the development of brains, research interest tends to focus on presumably constructive and progressive processes under the influence of natural selection. Particularly in the case of human brains and their evolution, it is generally assumed that the neurological differences underlying the complexity of human language abilities must have arisen due to progressive improvements of function via selection favoring these traits. In this talk I will explore an alternative possibility: that devolutionary loss-of-function due to reduced selection,
including degradation of developmental-genetic specificity, may contribute to the evolution of novel complex neural functions, such as language. The general logic of this argument originates from a critique of a commonly cited evolutionary mechanism: the Baldwin Effect. Although this theoretical â€œeffectâ€ is often invoked as an evolutionary mechanism leading from functional plasticity to increased specificity of genetic control, biological examples and simulation studies will be presented that show that the opposite effect is more likely, and also that there are other surprising correlates of this process. An animal exampleâ€”song production in a domesticated species of finchâ€”illustrates this effect and its paradoxical consequence. In this breed, increasingly complex song structure, expanded involvement of forebrain mechanisms, greater flexibility of behavior, and a larger contribution from social learning evolved without positive selection for these traits. Instead, these birds were bred for feather coloration. Absence of selection on song appears to have led to evolutionary degradation of song control specificity and with it unmasking of otherwise hidden synergies among diverse brain systems able to play some role in song structure. These results suggest some informative parallels with features of human language functions, and the possibility that regressive evolutionary processes might play an important role in the evolution of biological complexity more generally.

Leeat Yariv - Conformity In The Lab
2006-03-06 00:00
Leeat Yariv: Caltech Division of Humanities and Social Sciences, UCLA Department of EconomicsIn this talk, I will briefly survey the existing literature on social learning and conformity (both theoretical and experimental) and then present evidence from an array of new experiments disentangling conformity, an intrinsic taste to follow others, from informational herding in a sequential choice setting. In these experiments, we use a design reminiscent of the standard social learning setup in which subjects choose the type of information they observe before making a decision. Namely, subjects choose between observing a private and informative signal or observing a social signal manifested in the history of play of predecessors who have not chosen a private signal. Even though the latter type is essentially a word of mouth signal, entailing no statistical information, a significant fraction of subjects choose it persistently. Allowing for payoff externalities by paying subjects according to a collective action chosen by a majority vote amplifies the results. So does an increase in the stakes. Our design allows us to rule out alternative explanations the literature proposes such as confusion and inequality aversion.

Teresa Seeman - Exploring a Bio-Psychosocial Model of Cumulative Risk â€“ Biological Pathways Linking Life Experience and Health Outcome in Aging
2006-02-27 00:00
Teresa Seeman : UCLA David Geffen School of Medicine Division of GeriatricsDr. Seeman will discuss evidence linking socio-economic, social and psychological resources to trajectories of health and aging and the multiple biological pathways through which these factors appear to impact on health outcomes over the life course. Possible sex and/or ethnic differences in these patterns of association will also be discussed.

John Patton - Coalitional Psychology and the Conundrum of Altruism: a case from the Ecuadorian Amazon
2006-02-13 00:00
John Patton: California State University Fullerton Department of AnthropologyThe search for solutions to the conundrum of altruism is a central focus of evolutionary approaches to the study of human behavior. The focus of this talk is to present data on cooperation collected among horticultural foragers in the Ecuadorian Amazon to argue that a better understanding of the conundrum of altruism, and its constraints, can be gained by examining human cooperation as an aspect of an evolved coalitional psychology. Coalitional psychology is that aspect of human nature designed to construct mental representations of coalitional structures, to triangulate oneself and others within coalitional structures, to reason about and pursue behavioral strategies within
coalitional contexts, and to evoke emotional states that led to actions that result from or create coalitional consequences. Apart from
explicit or implicit attempts to detect group boundaries (ethnic, spatial, or political) and the collection of basic demographic data,
evolutionary ethnographers do not routinely collect data on coalitional structures. Without such data it is difficult to assess the influences
of coalitional thinking on cooperation which predicts that people will weigh the costs and benefits of cooperating differently depending on
their position within their coalitional. Even in egalitarian societies some people are more equal than others. In this talk I will integrate
data on coalitional structure derived from network analysis techniques, with data on behavior within three separate domains of cooperation
(status allocation, meat sharing, and experimental economic games) to illustrate influences of an evolved coalitional psychology on patterns of human cooperation.

Gail Heyman - Children's Reasoning about People as Source of Information
2006-02-06 00:00
Gail Heyman: UCSD Department of PsychologyThe human capacity to acquire knowledge from others, rather than only relying upon what can be observed or experienced directly, opens vast opportunities for learning. As a result of this capacity, humans are highly adaptable across many contexts. However, the use of such
information can also pose difficulties. For example, sources may provide incorrect or misleading information, either intentionally or unintentionally. In this talk, I will focus on children’s evaluation of others as sources of information within one particular context: when
people talk about themselves. The findings I will present, which include data collected in the U.S. and in China, address how children’s reasoning is affected by the content of the message, and by the social context in which the communication occurs.

Rafael NuÃ±ez - Embodied Cognition, Objectivity, and Truth: Lessons from Mathematics and Spatial Construals of Time in Aymara
2006-01-30 00:00
Rafael NuÃ±ez: UCSD Department of Cognitive ScienceHow can we “objectively” share abstract entities with others, in a stable and consistent way? How can we evaluate “Truth” when purely imaginary entities are concerned? Mathematics provides a very intriguing case for studying these questions. Indeed, mathematics, on the one hand deals with purely imaginary entities (e.g., a Euclidean point has only location, but no extension! … And there is no such “real” thing in the entire universe!), and on the other hand, it provides extremely stable patterns of true-valued inferences (i.e., theorems) that once proved, stayed proved for ever (e.g., the Pythagorean Theorem). In this talk I will analyze these issues by looking at (1) my own work on the Cognitive Science of Mathematics (with George Lakoff) taking examples from set and hyperset theory, and (2) my field work in the Andes’ highlands studying–with convergent linguistic-gestural-ethnographic methods–a very peculiar form of spatial construal of time in the Aymara culture. I’ll address the question of the role of axiom systems in generating and sustaining truth, and will show that the nature of truth and objectivity in abstract conceptual systems lie on the intricacies of the underlying bodily-grounded human cognitive mechanisms (e.g., conceptual metaphors, metonymies, analogies, blends) that make them possible.

Steven Gaulin - A Real-World Foraging Task Yields a Female Advantage and Significant Content Effects.
2006-01-23 00:00
Steven Gaulin: UCSB Department of AnthropologyThough Silverman and Eals division-of-foraging-labor hypothesis cannot explain the cross-species distribution of sex differences in spatial ability, it does make a novel prediction: women will more accurately remember the location of stationary resources. Unfortunately, Silverman and Ealsâ€™ own tests of this hypothesis have yielded weak and inconsistent support, possibly because the tasks used to assess the hypothesized female advantage lack ecological validity. I will present results of a controlled field study carried out at a large farmers market. Women performed significantly better than men at remembering the location of food items they had tasted, but not at remembering the location of non-food landmarks. In addition, accuracy was significantly correlated with the caloric content of food items, suggesting specialization of this particular cognitive system.

Dan Posner - Ethnic Diversity and Public Goods Provision in Kampala, Uganda: An Experimental Approach
2006-01-09 00:00
Dan Posner: UCLA Department of Political Science

Craig McKenzie - Framing Effects and Rationality
2005-12-05 00:00
Craig McKenzie: UC San Diego Department of PsychologyFraming effects are said to occur when “equivalent” redescriptions of objects or outcomes lead to different preferences or judgments. For example, a medical treatment is seen more favorably when described as resulting in “90% survival” rather than “10% mortality.” Such effects are widely considered to be classic violations of rationality. However, if framing effects are to be considered irrational, it is not sufficient that the frames in question be logically equivalent. Instead, they must be information equivalent, which means that no choice-relevant inferences can be drawn from the speaker’s choice of frame. However, logically equivalent frames used by researchers are often information non-equivalent. For example, we have shown that a speaker’s choice of attribute frame “leaks” information about relative abundance, and that listeners “absorb” the information. Information leakage provides a natural (and rational) explanation of attribute framing effects. Extensions of the information leakage approach to framing effects in risky choice, inference tasks, consumer behavior, and policy defaults will also be discussed.

Gregory F. Grether - Environmental Change, Phenotypic Plasticity and Genetic Compensation
2005-11-28 00:00
Gregory F. Grether: UCLA Department of Ecology and Evolutionary BiologyNormal development depends on specific environmental inputs. Consequently, when a species encounters novel environmental conditions, some traits may develop abnormally. Changes in the environment can occur, for example, because of climate change or habitat degradation. Like genetic mutations, most environmental perturbations of development are detrimental, and thus natural selection would usually be expected to favor genetic changes that gradually restore the ancestral form of the trait in the new environment. I recently coined the term “genetic compensation” to describe this form of adaptive evolution. When genetic compensation occurs along a spatial environmental gradient, it partially or completely masks the effects of the gradient on trait development. This means that populations of a species that look the same in the wild may develop quite differently if placed in a common environment. In addition, genetic compensation may lead to a cryptic form of reproductive isolation between populations, explain some puzzling cases in which heritable traits exposed to strong directional selection fail to show the expected evolutionary response, and complicate efforts to monitor populations for signs of environmental deterioration. In this talk, I will explain how genetic compensation differs from related phenomena, such as genetic assimilation and canalization, and review putative examples to illustrate the above points.
