Role of habituation in the irrelevant sound effect: Evidence from the effects of token set size and rate of transition

The disruption of serial recall by irrelevant sound was explored by examining the effect of the number of different tokens (token set size) and by varying the transition rate between different tokens. Two sets of predictions were contrasted. One, based on changing state, posited that a mismatch in physical composition between immediately successive stimuli was the important factor, leading to the prediction that disruption would increase as the token set size increased from 1 to 2 but would show no increase above that. Another, based on habituation, predicted that increasing the set size would increase disruption monotonically, on the grounds that for a given exposure each token would be relatively less habituated. Generally, the results showed the most marked increase in disruption occurred when the token set increased from 1 to 2, giving some support to the changing state hypothesis.