George E. Briggs

On the nature of central processing in choice reactions.

A procedure for generating values of central processing uncertainty was developed from positive response data in a varied-set version of the Sternberg choice reaction task. This is a logical extension of a previously validated procedure for data from a fixed-set version of the same task. Both procedures provide information on the additive components of reaction time. It was concluded that S resolves more uncertainty in the varied-set than in the fixed-set situation. It was concluded also that S performs a rechecking operation prior to emitting a negative response, and this rechecking apparently involves less information than does the original testing for stimulus classification. This, in turn, suggests that rechecking is a self-terminating process with regard to display information. The results also imply that stimulus classification is partially serial and partially parallel, so a hybrid model may be appropriate for this task.

On the locus of the divided-attention effects"

Reaction times in a choice reaction task were used to localize the livided-attention effect (less proficient performance under dual than under ingle-taks conditions) in a sequential-stage model of human information processing. Experiment 1 eliminated a central (memory-dependent) processing tage, while Experiment 2 suggested that a stimulus sampling process within the hitial encoding stage was the locus of the effect. Thus, the effect was localized in the input, not the central or an output stage of processing. A slower stimulus ampling rate was indicated under dual-than under single-task conditions.

On the locus of the speed/accuracy tradeoff

A statistically significant interaction between visual noise level and accuracy level was obtained for reaction time data in the Sternberg choice reaction task. This suggests that the speed/accuracy tradeoff is localized in the initial stimulus encoding stage of processing, specifically in a stimulus sampling operation. A slower stimulus sampling rate was found under visual noise than was found with a noise-free display.