Modality independence of order coding in working memory: Evidence from cross-modal order interference at recall

Abstract

Working memory researchers do not agree on whether order in serial recall is encoded by dedicated modality-specific systems or by a more general modality-independent system. Although previous research supports the existence of autonomous modality-specific systems, it has been shown that serial recognition memory is prone to cross-modal order interference by concurrent tasks. The present study used a serial recall task, which was performed in a single-task condition and in a dual-task condition with an embedded memory task in the retention interval. The modality of the serial task was either verbal or visuospatial, and the embedded tasks were in the other modality and required either serial or item recall. Care was taken to avoid modality overlaps during presentation and recall. In Experiment 1, visuospatial but not verbal serial recall was more impaired when the embedded task was an order than when it was an item task. Using a more difficult verbal serial recall task, verbal serial recall was also more impaired by another order recall task in Experiment 2. These findings are consistent with the hypothesis of modality-independent order coding. The implications for views on short-term recall and the multicomponent view of working memory are discussed.

Keywords:

• Working memory
• Serial recall
• Cross-modal interference

Notes

¹I am indebted to Robert H. Logie (personal communication, September 2009).

²Nowadays serial recall is often scored as the number of items correctly recalled in their serial position. In the present experiments, the participants were not instructed to indicate the positions that were skipped in their recall. The visuospatial tasks were recorded by the computer program, and no button was provided to indicate a forgotten position in the recall sequence. Similarly, in verbal serial recall, participants were not instructed to say “blank” for the forgotten positions. Whereas the average number of skipped or forgotten positions in the 5-item sequences of the primary task was low in Experiment 1 (M = 0.19), the 7-item sequences in Experiment 2 provided more opportunity for skipping or forgetting (M = 0.84). It is important to note, though, that performance registration in the present study does not allow a clean distinction between skipped positions and forgotten items. Given these circumstances, a relative scoring scheme yields the best estimate of the serial recall performance. Due to the loss of some relevant information, an absolute scoring of the serial recall underestimates the serial recall performance in the present data. Nevertheless, using absolute scores instead of relative scores yields similar results as reported here, but with less statistical power.

³As it happens, two memory tasks are presented per trial. Each task occurred only once throughout the experiment, so that on each trial, a unique trial pair was used. Therefore it suffices to include a random factor that represents the task pair on each trial.

⁴The contrast between single-task and dual-task condition is deliberately not labelled as “Load” because the difference between single-task and dual-task recall not only is affected by the absence or presence of an embedded task but also depends on the duration of the retention interval (immediate in single-task recall and delayed in dual-task recall). In principle, it is possible to use retention intervals of equal duration in the two conditions. However, when the single-task recall is delayed, and the recall interval is unfilled, recall is not expected to differ much from an immediate recall (because rehearsal is possible). Imposing rehearsal-prevention during the single-task retention interval would turn the single-task condition into a dual-task condition, and this would obscure the contrast between single-task and dual-task recall.