The preparation effect in task switching: Carryover of SOA

Altmann, Erik M. · 2004 · OpenAlex-citations

DOI: 10.3758/bf03195828

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Summary

This paper investigates the "preparation effect" in task-switching paradigms, specifically examining whether the reduction in switch costs associated with longer stimulus onset asynchronies (SOAs) depends on participants' exposure to multiple SOA levels. The preparation effect, a robust finding where longer intervals between task cues and stimuli reduce the latency cost of switching tasks, is typically observed in within-subjects designs. However, previous studies using between-subjects designs often failed to replicate this effect, raising questions about whether the effect is a genuine cognitive phenomenon or an artifact of experimental design involving carryover effects. The author tests two theoretical perspectives: the "reconfiguration view," which posits a dedicated switching mechanism that benefits from preparation time, and the "encoding view," which suggests that general perceptual or memory encoding processes benefit from longer SOAs regardless of task continuity. To address these questions, the author conducted three experiments using an explicit cuing paradigm where participants judged the height or width of rectangles. Experiment 1 employed a within-subjects design with randomized SOAs (100 or 900 msec). Results replicated the standard preparation effect, showing reduced switch costs at longer SOAs. Crucially, analysis revealed that this effect was more pronounced when the SOA switched from the previous trial, indicating a carryover effect where exposure to varying SOAs influenced performance. Experiment 2 used a within-subjects design with blocked SOAs. The preparation effect persisted, demonstrating that the carryover influence of SOA exposure lasted across entire blocks of trials. Experiment 3 utilized a between-subjects design, where participants were exposed to only one SOA level, and included explicit instructions to use the SOA for preparation. Despite adequate statistical power and instructions, no preparation effect was observed; switch costs did not decrease with longer SOAs. The findings indicate that switch preparation is contingent on participants being exposed to multiple levels of SOA within the same session. The absence of the effect in the between-subjects condition suggests that the cognitive system reacts "lazily" when exposed to a single, constant SOA, failing to adjust preparatory parameters. These results favor the encoding view of cognitive control, implying that the processes benefiting from preparation time are general encoding mechanisms rather than a specialized task-switching mechanism. The study concludes that the preparation effect is not a fixed property of task switching but is modulated by the variability of the experimental context, challenging interpretations that rely solely on within-subjects manipulations.

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• task switching