Examining the causal relationship between repetitions and rehearsals in serial recall and free recall

Four experiments examined the causal relationship between rehearsal and immediate serial recall (ISR) and immediate free recall (IFR). Experiments 1 and 2 manipulated the number of repetitions (Experiment 1) and rehearsals (Experiment 2) afforded to three-word lists prior to a variable retention interval in a modified Brown-Peterson task. Consistent with prior findings, serial recall declined precipitously with filled retention intervals of increasing duration in both experiments. Critically, we found that increased rehearsals resulted in increased serial recall; but owing to ceiling effects at 0s, the rehearsal benefit was only detectable at intervals of 3s and greater. Experiment 3 examined the effects of repetitions and delay on the recall of six-word lists in both ISR and IFR tasks. Recall increased with the number of repetitions and decreased with increased delay in both tasks; the positive effects of repetitions were significant even with immediate testing. Experiment 4 manipulated the number of words (between 1 and 6) that participants were instructed to cumulatively rehearse using the maxispan procedure with lists of six words. Recall in both tasks increased as the number of to-be-rehearsed words increased from 1 to 4. However, we found no further improvement in recall in either task when 5 or 6 words were to-be-rehearsed. Our findings help reconcile seemingly contradictory findings by showing that the effects of rehearsal, repetitions and delay in ISR and IFR are far more similar than previously thought, with there being a positive, but limited, causal relationship between rehearsal and recall in both tasks.