For each of 107 rats, varying in age from 30 to 390 days, starting latency, distance traversed, and time spent sniffing were measured in an open field containing 15 small objects. Exploration was inversely related to age on all 3 measures, and females showed more exploration than males. Exploration decreased from the first to the third testing day, and the decrements were greater in the older groups. Lowered general activity and lesser arousal in the older groups were hypothesized as explanatory factors. From Psyc Abstracts 36:04:4EF86F. (PsycINFO Database Record (c) 2006 APA, all rights reserved)