1. A Human Analogue of Rat Food Hoarding Behavior: Searching Path Kinematics Influence the Accuracy of Dead Reckoning S.N. Choudhry; M.M. Martin; D.G. Wallace* Dept Psychology, Northern Illinois Univ., DeKalb, IL, USA Introduction Evolution has provided animals with multiple navigational strategies to remain orientated under changing environmental conditions. As an animal travels through an environment, it generates an online record of its movements. Dead reckoning involves using this record to plot a direct path to the start location independent of environmental familiarity or visual cue availability. Theories of dead reckoning posit topographic and kinematic characteristics of movement as critical factors in determining an organisms ability to return to the start location; however, few studies have directly measured these movement characteristics during dead reckoning. The current study investigates human and rat movement characteristics while searching for randomly located rewards without access to visual information. Methods Under completely dark conditions, rats (4 female Long Evans) were provided with a refuge that permitted access to a circular table where food pellets were randomly located. Humans were blindfolded and given either 30 (n=10), 60 (n=10), or 120 (n=10) seconds to search for an ostensible hidden coin using a metal detector in a large outdoor area (12m x 21m). After location of the food pellet (rats), or the designated searching time elapsed (humans), rats carried the food pellet to the refuge and humans were instructed to return to the start location. Figure 2: Searching and homeward paths from one rat under dark conditions (Left). Rats searching paths are a series of direct progressions. Homeward segments are relatively fast non- circuitous paths (Right). Figure 1: Rat testing apparatus with topographic and kinematic profiles for a single food hoarding trip. Figure 3: Rat head directly to the home base after locating the food pellet. Figure 4: During the searching path, linear speed and path curvature are negatively correlated Figure 6: Human searching (A, B, & C) and homeward (D, E, & F) segments are plotted for the 30 sec (A & D), 60 sec (B & E), and 120 sec (C & F) groups. Figure 5: Human testing environment with topographic and kinematic profiles for a single 60 second trip. Figure 8: Reliability of returning to the start location varied as a function of the searching duration. Figure 9: The relationship between linear speed and path curvature varied as a function of searching duration. Conclusions Humans and rats display similar movement organization while navigating without access to visual information. Disruption of this movement organization in humans was associated with increased variability in returning to the start location. Correspondence: Douglas G. Wallace: dwallace@niu.edu www.niu.edu/user/tj0dgw1 Figure 7: Human searching paths are a series of direct progressions. Homeward segments are relatively fast non-circuitous paths 995.21