JACKSON, MASON CALVIN, JR.

Eighteen rats were used to study two procedures for the
extinction of discriminated avoidance. One group (OE) was
placed on extinction defined by presenting shocks as programmed
but independently of the S's responses, while the other group
(CE) was placed on classical extinction defined by the removal
of all shocks. The two procedures were compared in terms of
rate of decline and terminal level of extinction performance.
In addition, the two groups were placed on a discrimination
reversal task in order to assess each procedure's effects on
a new learning problem. The CE group reached a lower level of
extinction performance in a fewer number of blocks than the
OE Ss. Furthermore, the CE Ss were inferior to the OE Ss in
terms of discrimination reversal performance as well.
An interpretation of the results in terms of the removal
and reinstatement of cues was offered although an alternative
explanation relating to a change in the motivational states
of the two groups during extinction was also presented. The
interpretation in terms of the presence or absence of cues
seemed to account for more of the present findings than the
traditional one advocating changes in motivational levels
resulting from the two divergent extinction operations.