Effects of a Subsidiary Task on Short‐term Memory

If there is a limited‐capacity mechanism in STM then introducing a concurrent subsidiary task should adversely affect recall. Two experiments on free recall were conducted with card sorting as the subsidiary task. In the first experiment subjects dealt cards into one pile, into two piles by colour, or into four piles by suit while lists of common English words were being read. Subjects sorted cards only during presentation of the lists. As the subsidiary task became more demanding the number of words correctly recalled decreased. In the second experiment sorting by suit was combined with free recall, and the payoffs (relative importance of the two tasks) were varied. Performance on both the recall and the card sorting tasks deteriorated as the other task was stressed. Differences in recall could not easily be attributed to differences in original learning, and the results suggested that the subsidiary task interfered with rehearsal and/or decreased total presentation time for free recall.