Large numbers of possible cues for spontaneous alternation by rats in T mazes were tested both in isolation and in combination in an attempt to discover which stimuli determine the response. Free-trial spontaneous alternation represents the addition of a relatively weak odor-trail avoidance and a much more powerful tendency to turn in opposite directions at a choice point. No other effective alternation cues could be found, and the magnitude of these 2 tendencies was sufficiently high to account for all observed alternation. It is suggested that rats, at least, have a sense of relative direction or position in space, and that the receptors are located in the inner ear. (17 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)