LONG-TERM AND TRANSITORY INTERFERENCE EFFECTS

If animals receive inescapable electric shocks, their subsequent avoidance-escape learning is poor. This phenomenon, which can be called the interference effect, was studied in rats. Depending on the parameters of the inescapable shock used, there exists a transitory effect and a separable, more permanent, long term interference effect. The long term effect was investigated, showing that it required inescapable shocks of at least 5 s duration in order to develop and was still evident 1 wk after such inescapable shock. It is suggested that, whereas the transient effect is produced by a short lived neurochemical change, the long term effect is mediated by a learned response. Consistent with this differentiation, the interference effect measured 30 min after inescapable shock did not occur when animals had been repeatedly exposed to the type of inescapable shock that produced the transitory effect, whereas the interference effect measured 72 h after inescapable shock became more pronounced when animals had been repeatedly exposed to the type of inescapable shock that produced the long term deficit. Aspects of the data suggest that learned helplessness is not the basis of the long term interference phenomenon.