03/09 Laurie Santos, Yale University - Abstract
03/23 Tatsuya Kameda, Stanford University - Abstract
03/30 Mel Goodale, University of Western Ontario - Abstract
04/06 Michael Spivey, University of California, Merced - Abstract
04/13 Angela Yu, University of California, San Diego - Abstract
04/20 Jeff Elman, University of California, San Diego - Abstract

Abstract

3/9: Laurie Santos, Yale University
Title: The Evolution of Irrationality: Insights from Non-Human Primates
Abstract: My talk will explore the origins of our judgment and decision-making heuristics. Specifically, I will explore the possibility that some aspects of adult human irrational decision-making might be shared with non-human primates and human children. I will then attempt to use a comparative-developmental approach to directly address the origins of several classic human irrationalities, such as the anchoring bias, cognitive dissonance, loss aversion and reference dependence. I will then discuss why such irrationalities may emerge so early in human development and evolution, with the hope of providing insight into the psychological machinery that drives both accurate and biased decision-making.

3/23: Tatsuya Kameda, Stanford University
Title: Groups as Adaptive Devices: Free-Rider Problems, the Wisdom of Crowds, and Evolutionary Games
Abstract: The behavioral ecology literature has shown that adaptive benefits accrued from group life include the reduction of predation risk, increased efficiency in the acquisition of food and other vital resources, opportunities for social learning, etc. These findings suggest that, despite inherent conflicts of interest among members, groups consequentially serve as adaptive devices for individual survival in natural environments. Although psychological research on small groups has addressed conceptually parallel issues including the efficiency of group performance, the linkage to behavioral ecology has never been explicit. This talk explores the applicability of behavioral ecological theory in the study of human group behavior.

3/30: Mel Goodale, University of Western Ontario
Title: Acting without thinking: When do visually-guided actions escape conscious control?
Abstract: Human beings are capable of reaching out and grasping objects with great accuracy and precision – and vision plays a critical role in the control of this ability. The visual guidance of these skilled movements, however, requires transformations of incoming visual information that are quite different from those required for visual perception. For us to grasp an object successfully, our brain must compute the actual (absolute) size of the goal object, and its orientation and position with respect to our hand and fingers – and must ignore the relative size or distance of the object with respect to other elements in the visual array. These differences in the required computations have led to the emergence of dedicated visuomotor modules in the dorsal visual stream that are quite separate from the networks in the ventral visual stream that mediate our conscious perception of the world. Although the identification and selection of goal objects and an appropriate course of action depends on the perceptual machinery of the ventral stream and associated cognitive modules in the temporal and frontal lobes, the execution of the subsequent goal-directed action is mediated by dedicated on-line control systems in the dorsal stream and associated motor areas. But even though the dorsal stream may allow an observer to reach out and grasp objects with exquisite ease, it is trapped in the present. By itself, the dorsal stream can deal only with objects that are visible when the action is being programmed. The ventral stream, however, allows an observer to escape the present and bring to bear information from the past – including information about the function of objects, their intrinsic properties, and their location with reference to other objects in the world. Ultimately then, both streams contribute to the production of goal-directed actions.

4/6: Michael Spivey, University of California, Merced
Title: On the Continuity of Mind
Abstract: Rather than a sequence of logical operations performed on discrete symbols, real-time cognition is better described as continuously changing patterns of neuronal activity. The continuity in these dynamics indicates that, in between describable states of mind, much of our mental activity does not lend itself to the linguistic labels relied on by much of psychology. I will discuss eye-tracking and computer-mouse-tracking evidence for this temporal continuity in spoken word recognition, sentence comprehension, categorization, and even decision-making. I will also provide simulations and geometric visualizations of mental activity depicted as a continuous trajectory through a neuronal state space. In this theoretical framework, close visitations of labeled attractors may constitute word recognition events and object recognition events, but the majority of the mental trajectory traverses unlabeled regions of state space, resulting in multifarious mixtures of mental states.

4/13: Angela Yu, University of California, San Diego
Title: Sequential Effects: Irrational Superstition or Adaptive Behavior?
Abstract: Just as visual illusions reveal principles and mechanisms underlying natural visual processing, "cognitive illusions" can provide similar insight into the computations underlying decision-making. In a variety of behavioral tasks involving randomized sequences of stimuli, subjects exhibit an odd "sequential effect": their responses are facilitated by chance runs of repetitions and alternations in stimulus identity, and are hampered by violations of such transient local patterns. Such behavior is sub-optimal in the context of the task, since these transient patterns are spurious and have no true predictive power of future stimuli. We hypothesize that this apparently superstitious behavior may in fact reflect the engagement of adaptive mechanisms that are critical for responding to environments containing statistics that change over time. We use a normative Bayesian framework to show that a prior belief in changing statistics is sufficient to produce the type of sequential effects observed in subjects' behavior. The Bayesian algorithm is shown to have an approximately linear dependence on the history of past observations, where the dependence decays exponentially into the past; this exponential decay is also apparent in human and monkey behavior, as we found by re-analyzing data from published studies. We show that the necessary computations can be implemented by neurons with dynamics previously thought to underlie a variety of sensory processing and decision making computations. Our work provides a unifying account of how decision-making SHOULD adapt to a changing environment, a functional theory for WHY subjects exponentially discount the past, as well as a principled hypothesis of HOW neurons can implement the necessary computations.

4/20: Jeff Elman, University of California, San Diego
Title: The role of event knowledge in sentence processing: Arguments against a mental lexicon
Abstract: For many years, rules were where the action lay in language research. Words were seen as arbitrary, unsystematic, and relatively uninteresting. Over the past decade, however, there has been increasing interest in the lexicon as the locus of users' language knowledge. There is now a considerable body of linguistic and psycholinguistic research that has led many researchers to conclude that the mental lexicon contains richly detailed information about both general and specific aspects of language. Words are in again, it seems. But this very richness of lexical information poses representational challenges for traditional views of the lexicon. In this talk I will present a body of psycholinguistic data, involving both behavioral and event-related potential experiments, that suggest that event knowledge plays an immediate and critical role in the expectancies that comprehenders generate as they process sentences. I argue that this knowledge is on the one hand precisely the sort of stuff that on standard grounds one would want to incorporate in the lexicon, but on the other hand cannot reasonably be placed there. I suggest that in fact, lexical knowledge (which I take to be real) may not properly be encoded in a mental lexicon, but through a very different computational mechanism.