Voluntary attention and the spacing effect

Three experiments were done to test the hypothesis that the spacing effect results from a voluntary decision by the subject to pay little attention to the second presentation (P2) of an item when it occurs shortly after the first (P(1))- In all three experiments, the spacing of repetitions was varied. In Experiment I, allocation of attention was manipulated by pairing P2 of some pictures with a signal that indicated high payoff for later retention. In Experiment II, attention was controlled more directly by requiring the subject, in one condition, to recite words aloud. In both experiments, the dependent variable was judged frequency. In neither experiment did the effect of the attention manipulation interact with that of the spacing of repetitions. In Experiment III, the number of eye fixations given a picture was taken to be a measure of attention. The number of fixations dropped from P1 to P2 to P3, but was unaffected by the spacing of repetitions. The experiments provide no support for a voluntary attention explanation of the spacing effect.