Categorization by movement direction: Retrieval-induced forgetting of motor sequences grouped by motion features

Abstract

We investigated the organized storage of motor sequences in memory by assuming that processes related to interference at retrieval are indicative of memory organization. Effects resulting from these processes, thus, would allow inferences on how motor sequences are represented and organized. Participants learned motor sequences that were categorized by the direction of the initial movement. The subsequent selective retrieval of a subset of sequences of one category resulted in retrieval-induced forgetting (RIF) for the non-retrieved sequences of the same category. RIF occurred in an explicit recall test (Experiment 1), as well in an implicit test assessing memory with novel cues (Experiment 2). The results suggest that RIF affected motor programmes and that other cues as the used effectors (here movement direction) can be used for the organization of procedural memory. Basic retrieval dynamics apparently operate within the declarative and procedural systems in a similar way.

Keywords:

• Categorization
• Body movement
• Organization in memory
• Procedural memory

This work was supported by the German Research Council (DFG) under Grant TE 891/3–1.

Notes

¹For half of the participants, the instructions had already made it clear that there were two groups of mouse movement sequences, namely a group of mouse movement sequences starting with a movement forwards and a group of mouse movement sequences staring with a movement backwards. Yet, when we entered this variable as a factor in a 2 (condition: with categorization statement, no categorization statement) × 2 (sequence type: Rp−, Nrp1) ANOVA, it did not influence the RIF effect, F < 1, that is, explicitly stating that the sequences were split into two groups with the same initial movement direction was not a precondition for participants to use movement direction for categorization.

²The Nrp sequences differed with regard to the degree of overlap of the second movement with Rp+ sequences. In an additional analysis, we examined whether RIF did not only occur as a consequence of the shared feature of initial movement but also in dependence of another shared feature, namely the direction of the second movement (either to the left or to the right). Nrp1 (and correspondingly Nrp2) sequences either overlapped with one or with two Rp+ sequences in the direction of the second movement. If an overlap in this feature entailed RIF for Nrp sequences, the difference in recall of Rp− and Nrp1 sequences, as well as the difference in recall of Rp+ and Nrp2 sequences would depend on the assignment of Nrp sequences to Nrp1 and Nrp2. We tested this prediction by a 2 (Rp−, Nrp1) × 2 (assignment of Nrp sequences to Nrp1 or Nrp2) ANOVA with repeated measures on the first factor and a 2 (Rp+, Nrp2) × 2 (assignment of Nrp sequences to Nrp1 or Nrp2) ANOVA with repeated measures on the first factor. The interaction was not significant in either analysis, Fs < 1.