Predictability as a task demand in single‐trial free recall

In a series of five single‐trial free recall experiments it was demonstrated how manipulations of predictability in a list learning task caused reliable effects on the recency portions of the nominal serial position curve. Predictability was defined as knowledge of when the next item in the list should appear ( interval predictability) and knowledge of when the list should end and thus when recall could start ( signal predictability). Predictability was manipulated by varying the inter‐item intervals within a list according to different “encoding functions”, e.g. a successive increase (Condition I ) or decrease (Condition D ) of the inter‐item intervals. Predictability was also manipulated by means of post‐list recall signals. The data obtained show, that depending on how the interval and the signal predictabilities were manipulated, either Condition I or Condition D lists could be made more beneficial to the recall of recency items than lists with constant inter‐item intervals (Condition C ). Previous encoding, storage and retrieval models were found not to give satisfactory accounts of the obtained recency effects. Neither could any traditional rehearsal model explain the data. Instead it is proposed that the predictability of stimuli in a list learning task explains how changes in recall of recency items come about. It was also hypothesized that the temporal demands, afforded to the subjects by the different encoding functions, explained the obtained output order variations.