On the interaction between memory scanning and response set.

In the first of two item recognition experiments, a study by Egeth, Marcus, and Bevan (1972) was duplicated, but using a within-Ss design. Consistent with their findings, analogous differences obtained between mean RTs to positive set sizes of one and three were found to be significantly greater when Ss pressed two different keys to indicate whether or not a test letter was a member of the positive set (two-response condition) than when Ss pressed a single key to indicate only that a test letter was a positive set member (one-response condition). The number of set sizes used and results obtained for the two-response condition, which were inconsistent with characterization of the search process as either serial and exhaustive or serial and self-terminating, both limited and complicated interpretation of the obtained interaction. Further, these results suggested that the procedures used differed in important ways from those known to consistently produce linear and parallel item recognition functions for both positive and negative trials for the two-response condition. In Experiment II, those item recognition procedures which are known to allow serial exhaustive search to occur were used, and data were collected for four positive set sizes. Reaction time was a linear function of set size for both response conditions, the slopes of the functions did not differ significantly, and absolute slope values were consistent with previously reported findings for the two-response condition and letter stimuli. It is concluded that response requirements sometimes have effects on memory scanning (the slope of the item recognition function). Such an effect was observed when the experimental conditions were such as to allow neither serial and exhaustive nor serial and self-terminating memory search to occur. But, response requirements do not always have effects on memory scanning, and this was found to be the case when the experimental conditions were such as to allow serial and exhaustive memory search to occur and it was shown to occur.