TESTING MODELS OF THE IRRELEVANT SPEECH EFFECT ON WORKING-MEMORY WITHEVENT-RELATED POTENTIALS

The impairment of short-term recall when irrelevant auditory material is presented together with the items to be memorized - the irrelevant speech (IS) effect - has been explained by two competing theories. Bad deley assumes that the IS effect is based on the phonological similari ty between the material to be memorized and the irrelevant material. I n contrast, Jones conceives the IS effect to be due to the sound varia bility within the irrelevant stream. In the present study we tested th ese theories by means of recording event-related potentials (ERPs) to visually presented letters alternating with more or less disturbing ir relevant auditory material selected as far as possible according to th e critical conditions formulated by each model. Although Baddeley's IS condition was more detrimental to performance than the one according to Jones. a significant IS effect in ERPs was found only for the latte r. Therefore it appears that the IS effect may have two different sour ces, possibly in line with each of both theories.