Acquisition and Extinction of the Conditioned Eyelid Response in the Squirrel Monkey as Functions of the CS-UCS Interval

Interstimulus intervals of .5, 1.0, 2.0, and 4.0 sec. were compared for effectiveness in conditioning the blink reaction of the squirrel monkey ( Saimiri sciurea). Control groups receiving unpaired stimulation, CS-only, and UCS-only were run at each level of ISI. Statistically reliable evidence of conditioning was found in the acquisition data only at .5 sec., with the performance of all groups increasing as a function of ISI. Superior resistance to extinction in the paired group was also discernible only at .5 sec. although the combined performance in extinction of the paired and unpaired groups at 2.0 and 4.0 sec. exceeded that of the .5- and 1.0-sec. groups. A replication experiment using a within-subjects design magnified the interval effect in both acquisition and extinction. The results suggest the operation of pseudoconditioning and sensitization of spontaneous blinks in addition to revealing marked differences from human eyelid conditioning data, particularly in extinction.

Effects of Stimulus Change and Drive Level on Extinction of the Conditioned Eyelid Response

Rate of extinction of the conditioned eye blink was investigated as a function of maintained drive level in extinction and amount of stimulus change from conditions of acquisition to those of extinction. 50 Ss were given 90 acquisition trials under a partial reinforcement schedule in which the UCS was either delayed or omitted on half the trials. Half of the Ss conditioned under each procedure were given 20 extinction trials with the UCS delayed and half were extinguished with the UCS omitted. There was no evidence for an effect of either drive or amount of stimulus change determining rate of extinction.