The interaction of response complexity and instructional set

This study investigated the interaction of experimental instructions and response complexity in an attempt to provide a possible explanation for some of the equivocalness in the programming time literature. Response complexity was manipulated by varying the accuracy required of subjects striking circular targets in a simple reaction time paradigm. Subjects were tested on two days, one week apart, during which experimental instructions emphasized either leaving the start position as soon as possible (initiation emphasis) or completing the response with a rapid but smooth movement (form emphasis). Subjects had shorter reaction times but longer movement times when they performed under initiation-emphasis instructions rather than under form-emphasis instructions. Furthermore, in contrast to form-emphasis conditions, there was no effect of response complexity on reaction time in conditions of initiation emphasis. It appears that subtle changes in experimental instructions can lead to very different patterns of reaction time and movement time data. These findings highlight the need for caution in preparing subject instructions in response programming experiments.     

Sequence of preparatory set for response movement

Electromyographic reaction times (EMG-RTs) of the right biceps brachii muscle were examined for two movement patterns, elbow flexion and forearm supination, in 8 healthy male subjects under simple and complex RT conditions with varied preparatory intervals (PIs): 0, 200, 400, 600, and 800 msec. In the simple RT condition, the subject was informed of the movement patterns to be performed prior to beginning the trials. In the complex RT condition the subject had to choose one of the two movement patterns at the time of the presentation of a warning signal. The results indicated that: (1) compared with the simple RT condition a delay of about 100 msec. in over-all mean EMG-RT was observed at PI = 0 msec. in the complex RT condition; (2) the difference of over-all mean EMG-RT between the two RT conditions disappeared when PI = 400 msec.; and (3) the difference in EMG-RTs between flexion and supination in the complex RT condition became the same as that in the simple RT condition when PI = 700 msec. It is assumed that the preparatory set for response movements is organized in an order, resulting in the differentiation of RT.     

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.     

Selective attention and response set in the Stroop task

Response set membership contributes much to the interference in the color-word Stroop task. This may be due to selective allocation of attention to eligible responses or, alternatively, to greater inhibition of distractors that are not responses. In the present article, we report two experiments that were designed to adjudicate between these accounts. In Experiment 1, membership was manipulated on a trial-by-trial basis by cuing the possible responses for each trial. Response time (RT) was longer for distractors that corresponded to a cued, eligible response than to an ineligible one. This cuing effect was independent of the number of different responses. In Experiment 2, the distractor was cued on half the trials. Cuing the distractor decreased RTs on both incongruent and congruent trials. Vincentile analyses in both experiments revealed that the effects were constant throughout the entire RT distributions. These results suggest that response set effects arise because of selective allocation of attention to eligible responses.