Information interference and loss in a dual task situation: Task 1, choice reaction time; Task 2, unspeeded recall

The extraction and maintenance of second task information was explored in four dual task experiments. A variant of the psychological refractory period procedure was used with the first task, a speeded choice reaction to a tone and the second task, the unspeeded recall of letter triplets. Prior research had shown that recall accuracy dropped as the stimulus-onset asynchrony (SOA) decreased and task overlap increased. This could be due to interference with extracting perceptual information or to loss of the information while awaiting central resources. All four experiments showed evidence of interference, with the accuracy of recall for the first letter recalled relatively unaffected by SOA but with accuracy for later letters dropping as SOA decreased. Two of the experiments showed evidence for loss of second task information, with accuracy lower on trials with longer first task reaction times. The two other experiments showed loss of information when either the response complexity of Task 1 or the perceptual encoding difficulty was increased, increasing the processing time. The observed interference was attributed to slowed extraction of perceptual information. The observed loss was consistent with the encoded information being held in a fragile temporary store, susceptible to loss until consolidated into short-term memory. The evidence showed that the interference and the loss were independent processes.