Abstract
Positive effects of variable practice conditions on subsequent motor memory consolidation and generalization are widely accepted and described as the contextual interference effect (CIE). However, the general benefits of CIE are low and these benefits might even depend on decreased retest performances in the blocked-practicing control group, caused by retroactive inhibition. The aim of this study was to investigate if CIE represents a true learning phenomenon or possibly reflects confounding effects of retroactive inhibition. We tested 48 healthy human participants adapting their reaching movements to three different force field magnitudes. Subjects practiced the force fields in either a Blocked (B), Random (R), or Constant (C) schedule. In addition, subjects of the Blocked group performed either a retest schedule that did (Blocked-Matched; BM) or did not (Blocked-Unmatched; BU) control for retroactive inhibition. Results showed that retroactive inhibition did not affect the results of the BU group much and that the Random group showed a better consolidation performance compared to both Blocked groups. However, compared to the Constant group, the Random group showed only slight benefits in its memory consolidation of the mean performance across all force field magnitudes and no benefits in absolute performance values. This indicates that CIE reflects a true motor learning phenomenon, which is independent of retroactive inhibition. However, random practice is not always beneficial over constant practice.
Highlights
It is widely accepted that variable practice conditions can be beneficial for motor memory consolidation (Schmidt, 1975; Shea and Morgan, 1979)
Classical explanations include the elaboration hypothesis (Shea and Zimny, 1983), the reconstruction hypothesis (Lee and Magill, 1983), and the retroactive inhibition hypothesis (Shea and Titzer, 1993). It is still unsolved whether contextual interference effect (CIE) stems from an increased memory consolidation due to the random practice condition or by a decreased retention performance of the blocked practice condition
Memory consolidation was significantly stronger for the Random group compared to the BM group (F(1,22) = 5.65, p = 0.029, ηp2 = 0.20) and descriptively stronger to the BU group [F(1,22) = 5.49, p = 0.054, ηp2 = 0.20, for FDR corrected time∗group interactions with factors time (Practice LT, Posttest ALL) and group (BM, R; BU, R)], which confirms the CIE
Summary
It is widely accepted that variable practice conditions can be beneficial for motor memory consolidation (Schmidt, 1975; Shea and Morgan, 1979). The contextual interference effect (CIE)—originally formulated by Battig (1972) for verbal learning—describes an increased retest and transfer performance (Shea and Morgan, 1979; Magill and Hall, 1990) due to highlyinterfering cognitive processes during random practice conditions (Kantak et al, 2010; Lage et al, 2015). Classical explanations include the elaboration hypothesis (Shea and Zimny, 1983), the reconstruction hypothesis (Lee and Magill, 1983), and the retroactive inhibition hypothesis (Shea and Titzer, 1993) It is still unsolved whether CIE stems from an increased memory consolidation due to the random practice condition (e.g., elaboration or reconstruction hypothesis) or by a decreased retention performance of the blocked practice condition (retroactive inhibition hypothesis). When retroactive inhibition was eliminated by using a reminder trial, no differences in memory recall were observed between random and blocked practice schedules (Shea and Titzer, 1993)
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