Changes in the Expression of Stimulus Selection: Blocking Represents Selective Memory Retrieval Rather Than Selective Associations

Abstract

Initial studies reporting changes in the expression of stimulus selection as a function of the length of the interval between training and testing have been restricted to the conditioned taste aversion procedure. The present study examined the influence of the length of retention interval on the stimulus selection phenomenon of blocking when external cues were used as conditioned stimuli and suppression of activity served as the measure of conditioning. Similar to findings in flavor aversion conditioning, the expression of blocking was dependent on the length of the interval between training and testing. The results indicate that blocking, like overshadowing, does not necessarily represent a failure in acquisition, but rather suggest an explanation of certain instances of blocking in terms of changes in the relative retrievability of learned associations over time.