Periodic behavior in a random environment.

Animals' tendency to search periodically in temporally random environments was studied by presenting rats with random-interval (RI) 60-s and 120-s schedules. Power spectra revealed a periodicity of responding of 20-50 s for all animals regardless of condition. A second periodicity of 5-10-s was strongest under the RI 60-s schedule. Optimality theory suggests that periodic responding is better than random responding in obtaining food sooner on average, but the theory does not account for multiple periodicities. These multiple periodicities also cannot be explained by a single-oscillator, information-processing version of scalar expectancy theory (J. Gibbon & R. M. Church, 1992) or by the behavioral theory of timing (P.R. Killeen & J. G. Fetterman, 1988). The periodicities are consistent with a connectionist version of scalar expectancy theory that has nonscalar emergent properties, including multiple periodicities that are not proportional to the rate of random events.