Priming and conservation between spatial and cognitive search

Priming and Conservation Between Spatial and Cognitive Search Thomas T. Hills (thills@indiana.edu) Department of Psychological and Brain Sciences 1101 E. 10 th St., Indiana University, Bloomington, IN, 47405 Peter M. Todd (pmtodd@indiana.edu) Program in Cognitive Science 1101 E. 10 th St., Indiana University, Bloomington, IN, 47405 Robert L. Goldstone (rgoldsto@indiana.edu) Department of Psychological and Brain Sciences 1101 E. 10 th St., Indiana University, Bloomington, IN, 47405 Significant evidence from various fields suggests that this relationship between spatial foraging and internal cognitive search is not just a consequence of convergent evolution, but one of evolutionary homology (Hills, 2006). Research from neuroscience, genetics, and human pathology provide evidence that molecular and neural mechanisms that developed over evolutionary time for the purpose of modulating between exploration and exploitation in spatial foraging have subsequently been exapted for the purpose of modulating attention. A key observation is that similar dopaminergic processes are used to modulate goal-directed behavior and attention in multiple behavioral modalities across species (Floresco et al., 1996; Watanabe et al., 1997; Wang et al., 2004; Schultz, 2004). Furthermore, numerous pathologies of goal-directed cognition (e.g., attention- deficit/hyperactivity disorder—ADHD, drug addiction, and obsessive-compulsive disorder) involve dopaminergic defects or respond to dopaminergic drugs in ways that are consistent with dopaminergic effects on spatial movement behavior, as in, for example, the nematode and the fruit fly (Berke et al., 2000; Nieoullon, 2002; Schinka et al., 2002; Hills et al., 2004; Kume et al., 2005). These observations suggest that spatial search in physical space and abstract search in a cognitive space share a common basis in the brain and may therefore share key control features. While prior work has shown that animal foraging theory can be successfully applied to human search behavior (Pirolli & Card, 1999; Wilke, 2006), these efforts have been made based on arguments for optimality or robust decision heuristics. An argument based on a common biological basis for goal-directed cognition, however, would mean that spatial and abstract foraging are not simply similar because of similar selective forces in the environment, but are, in fact, themselves constrained by similar underlying physiologies. Given this, if the search mechanisms for different domains are not independent of one another, then activity in one ‘environment’ may influence activity in another. In such a case, we would expect that differences in individual foraging behavior could be primed across spatial and abstract contexts. That is, prior experience with resource distributions in a spatial environment could prime foraging behavior in an abstract environment. Similarly, we would Abstract There is compelling molecular and behavioral evidence that human goal-directed cognition is an evolutionary descendent of animal foraging behavior. A key observation is that similar dopaminergic processes are used to modulate between exploratory and exploitative foraging behaviors and control attention across animal species. Moreover, defects in these processes lead to predictable goal-directed cognitive pathologies in humans, such as attention-deficit/hyperactivity disorder and Parkinson’s disease. However, the cognitive relationships between exploration in space and exploration in the mind have not been examined. Using a spatial foraging task with two treatment conditions (clumpy and diffuse), followed by a word search task involving patches of words to be found in letter sets, we show that individuals who experienced clumpy resource distributions in space behave as if resources are more densely clumped in the word search task, relative to those who experienced the diffuse spatial treatment. We show this is not a function of general arousal but is consistent with longer giving- up times in the word search task, which is a qualitative prediction of optimal foraging theory. We also show that behavioral tendencies during search are conserved within individuals: Those who explore more of the physical space leave letter sets sooner. Along with the biological evidence, our results support a general search process underlying cognition, which operates both in external and internal environments. Keywords: Goal-directed behavior; attention; animal foraging; foraging; dopamine; search; spatial search; word search; priming; individual differences; ADHD; Parkinson’s. Introduction More than a hundred years ago William James noted “We make search in our memory for a forgotten idea, just as we rummage our house for a lost object” (James, 1890, p654). This relationship is anecdotally supported by the fact that cognitive representations of spatial and semantic knowledge are often characterized as maps or networks (Steyvers & Tenenbaum, 2005; Tolman, 1948). Though these internal representations are specific to particular contexts, the search processes required to navigate them may not be. In all cases, cognitive navigation relies on appropriate modulation of attention between exploration and exploitation in ways fundamentally similar to the behavioral ecology of animal foraging (Kareiva & Odell, 1987; Walsh, 1996).