The duration of tonic immobility in guinea pigs.

Abstract

The duration of tonic immobility imposed by restriction of movement decreases as a function of repeated trials, declining to zero. In early stages of induction there is an initial tendency of du-ration to increase. In the main, the following hypothesis was supported by the results: "When animals are immobilized in daily testing sessions, duration first increases and then declines to zero, the initial increase being greater as the duration of the daily testing session lengthens.