[Frequency of acquired helplessness and initial probability of showing an elaborated reaction]

The defense reflex of random performance of instrumental reaction (RPIR) had been produced in rats with different probabilities which were equal to 0.5; 0.25; 0.125 and 0.05 in respective experimental groups. Learning of animals was found to take place much faster when probabilities of RPIR were equal to 0.125 and 0.25 as compared with 0.5 and 0.05 values. One third rats which learned at 0.05 and 0.5 probabilities did not produce the reflex; the decrease in aroused, fall of body weight and other disturbances were observed and these findings may evident development of acquired helplessness about. It is supposed that optimal circumstances are occurred at different probabilities of RPIR conditions.