Interference of concomitant tasks on simple reaction time: attentional and motor factors.

Simple reaction times to lateralized unstructured visual stimuli were measured in normal subjects while they were carrying out concomitant left hemisphere tasks. Three tasks were used. In the first task the subjects had to pay attention to strings of digits, acoustically presented, and detect letters randomly interspersed among the digits; in the second task the subjects had to memorize strings of acoustically presented digits; in the third task they had to repeat each digit of a string as soon as they heard it. In spite of the greater difficulty of the first two tasks with respect to the third one, only this last task, the only one requiring a verbo-motor response, produced a significant disadvantage for the left hemisphere responses to light. It is argued that in RT experiments a specific left hemisphere interference takes place when the secondary task requires the organization of a motor response

[Cognitive tasks and simple reaction times: new observations]. / Compiti cognitivi e tempi di reazione semplici: nuovi dati.

Simple reaction times to lateralized unstructured visual stimuli were studied in normal subjects while they were carrying out a concomitant task. In one task strings of four digits, randomly chosen from 1 to 9, were acoustically presented to the subjects who had to repeat them at the end of each presentation, in a second task again strings of four digits were presented and the subjects were asked to pay attention to the stimuli without memorizing them. In order to compel the subjects to listen carefully to the stimuli, in the second experiment, intermixed with the digits, a letter was occasionally presented and the subjects had to repeat it. It was found that the memory task facilitates reaction times mediated by the left hemisphere, whereas no hemispheric differences were found in the purely attentional task.