Task characteristics and the contextual interference effect.

The purpose of this exploratory study was to examine the influence of blocked and random practice on the acquisition and retention of a criterion multisegment motor task practiced alongside either two similar-distractors tasks or two different-distractors tasks. The random-practice similar-distractors group made more decision-making errors and performed the criterion task more slowly than the blocked-practice similar-distractors group during the acquisition phase. Following a brief filled retention interval, the blocked-practice similar-distractors group demonstrated a loss of acquired performance capabilities, whereas the random-practice similar-distractors group did not. The blocked- and random-practice different-distractors groups performed similarly throughout the experiment. Results are interpreted within Glenberg's component-levels theory, in which it was argued that random practice must stimulate the differential storage of multilevel contextual components associated with the multiple motor tasks being learned to produce a contextual interference effect. The theoretical and practical implications of differential storage versus nonrepetition as a function of random practice are discussed.