Otten, Cynthia S.

Twenty 100 day old male rats were trained to behavioral criterion in a CER paradigm. Two shock levels (.1 and .2 ma) were employed to establish these criteria. Half of the Ss reached medium suppression (suppression ratios between .39 and .11) of a bar pressing response; half achieved high suppression (suppression ratios less than .10). The animals were subsequently exposed to 15 daily sessions of FI training utilizing a head, panel pressing response for food. Five of the medium suppression group and five of the high suppression group were exposed to the conditioned suppression CS (a light) during the FI acquisition periods . The remaining rats underwent FI training in the absence of the CS. An Index of Curvature was employed to measure each FI period record and to indicate the degree of acquisition of FI scalloping. Analysis of variance for the four groups revealed only the progression over days to be a significant source of variation. Analysis of linear trend indicated a strong linearity in the variance over 15 days for all groups, but revealed no clear differences between the groups. Some tendencies indicate a slight superiority in acquisition by the medium suppression group which was exposed to the CS during FI training. The high suppression group which was exposed to the light was noticeably inferior in FI discrimination. These results possibly demonstrate an "arousal- interference" mechanism for the CER, but the data do not support the conclusion that the conditioned suppression signal (CS) has a differential effect on subsequent acquisition of an unrelated temporal discrimination. A history of shook treatment, or of CER training, may be responsible, however, for the overall poor acquisition of FI scalloping that was demonstrated by all four groups in this study.

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.