WORKING-MEMORY AND STIMULUS-INDEPENDENT THOUGHT - EFFECTS OF MEMORY LOAD AND PRESENTATION RATE

When not engaged in demanding tasks, we commonly experience streams of thoughts and images quite unrelated to immediate sensory input. Such stimulus-independent (SI) thoughts may be troublesome, as in worry, in somnia and depression. Previous research within a working memory parad igm suggested that SI thought production depended on central executive control resources. To explore this hypothesis further, we examined th e interference with SI thought production resulting from shadowing aud itorily presented digits compared to remembering them. Effects of stim ulus presentation rate and size of memory load were also examined. At slow presentation rates, remembering produced more interference than s hadowing. For shadowing, faster presentation produced greater interfer ence than slow presentation. In remembering, interference was not subs tantially affected by size of memory load, was greater when subjects r eported greater awareness of task stimuli, and was restricted to thoug hts forming parts of connected sequences. The results are consistent w ith the view that production of connected sequences of SI thoughts dep ends on central executive control resources, that tasks interfere with thoughts to the extent that they make continuous demands on these res ources, and that high subjective awareness of task stimuli is a marker that these resources are deployed to task management rather than thou ght production. The results are not consistent with Antrobus' view tha t interference with SI thoughts by tasks is simply a function of the r ate of processing information from external sources required by the ta sk.