Emergent Processes in Group Behavior

Just as networks of neurons create structured thoughts beyond the ken of any individual neuron, so people spontaneously organize themselves into groups to create emergent organizations that no individual may intend, comprehend, or even perceive. Recent technological advances have provided us with unprecedented opportunities for conducting controlled, laboratory experiments on human collective behavior. We describe two experimental paradigms where we attempt to build predictive bridges between the beliefs, goals, and cognitive capacities of individuals and group-level patterns, showing how the members of a group dynamically allocate themselves to resources, and how innovations are spread in a social network. Agent-based computational models have provided useful explanatory and predictive accounts. Together, the models and experiments point to tradeoffs between exploration and exploitation, compromises between individuals using their own innovations and innovations obtained from their peers, and the emergence of group-level organizations such as population waves, bandwagon effects, and spontaneous specialization.National Science Foundation Department of Educatio

Adaptive Group Coordination and Role Differentiation

Many real world situations (potluck dinners, academic departments, sports teams, corporate divisions, committees, seminar classes, etc.) involve actors adjusting their contributions in order to achieve a mutually satisfactory group goal, a win-win result. However, the majority of human group research has involved situations where groups perform poorly because task constraints promote either individual maximization behavior or diffusion of responsibility, and even successful tasks generally involve the propagation of one correct solution through a group. Here we introduce a group task that requires complementary actions among participants in order to reach a shared goal. Without communication, group members submit numbers in an attempt to collectively sum to a randomly selected target number. After receiving group feedback, members adjust their submitted numbers until the target number is reached. For all groups, performance improves with task experience, and group reactivity decreases over rounds. Our empirical results provide evidence for adaptive coordination in human groups, and as the coordination costs increase with group size, large groups adapt through spontaneous role differentiation and self-consistency among members. We suggest several agent-based models with different rules for agent reactions, and we show that the empirical results are best fit by a flexible, adaptive agent strategy in which agents decrease their reactions when the group feedback changes. The task offers a simple experimental platform for studying the general problem of group coordination while maximizing group returns, and we distinguish the task from several games in behavioral game theory

Relations Relating Relations

The aim of the current work is to incorporate structural information in judgments of similarity. According to the assumption of feature independence, h o w one feature affects similarity is independent of the values of the other features present. W e present three violations of this assumption, all arising from Uie influence of relations between features and of relations between relations. A shared relation is more important for similarity judgments if it cooccurs with (A) relations that augment the first relation by "pointing in the same direction" as the first relation, (B)relations which are themselves salient, and (C) salient relations that involve the same objects as the first relation. We interpret these results as suggesting that relations do not have separately determined weights or saliences; the weight of a relation depends the relational structure in which it exists. Relations influence each other by creating higher order relational structures, and also by affecting processing

Categorical Perception of Novel Dimensions

Categorical perception is a phenomenon in which people are better able to distinguish between stimuli along a physical continuum when the stimuli come from different categories than when they come from the same category. In a laboratory experiment with human subjects, we find evidence for categorical perception along a novel dimension that is created by interpolating (i.e. morphing) between two randomly selected bezier curves. A neural network qualitatively models the empirical results with the following assumptions: 1) hidden "detector" units become specialized for particular stimulus regions with a topologically structured competitive learning algorithm, 2) simultaneously, associations between detectors and category units are learned, and 3) feedback from the category units to the detectors causes the detectors to become concentrated near category boundaries. The particular feedback used, implemented in an "S.O.S. network," operates by increasing the learning rate of weights connecting inputs to detectors that are neighbors to a detector that produces an improper categorization

Improving Perception to Make Distant Connections Closer

One of the challenges for perceptually grounded accounts of high-level cognition is to explain how people make connections and draw inferences between situations that superficially have little in common. Evidence suggests that people draw these connections even without having explicit, verbalizable knowledge of their bases. Instead, the connections are based on sub-symbolic representations that are grounded in perception, action, and space. One reason why people are able to spontaneously see relations between situations that initially appear to be unrelated is that their eventual perceptions are not restricted to initial appearances. Training and strategic deployment allow our perceptual processes to deliver outputs that would have otherwise required abstract or formal reasoning. Even without people having any privileged access to the internal operations of perceptual modules, these modules can be systematically altered so as to better serve our high-level reasoning needs. Moreover, perceptually based processes can be altered in a number of ways to closely approximate formally sanctioned computations. To be concrete about mechanisms of perceptual change, we present 21 illustrations of ways in which we alter, adjust, and augment our perceptual systems with the intention of having them better satisfy our needs

How much to copy from others?The role of partial copying in social learning

One of the major ways that people engage in adaptive problemsolving is by copying the solutions of others. Most of the workon this field has focused on three questions: when to copy, whoto copy from, and what to copy. However, how much to copyhas been relatively less explored. In the current research, weare interested in the consequences for a group when its mem-bers engage in social learning strategies with different tenden-cies to copy entire or partial solutions and different complex-ities of search problems. We also consider different networktopologies that affect the solutions visible to each member.Using a computational model of collective problem solving,we demonstrate that strategies where social learning involvespartial copying outperform strategies where individuals copyentire solutions. We analyze the exploration/exploitation dy-namics of these social learning strategies under the differentconditions