Post-categorical auditory distraction in serial short-term memory: Insights from increased task load and task type

Task-irrelevant speech impairs short-term serial recall appreciably. On the interference-by-process account, the processing of physical (i.e., pre-categorical) changes in speech yields order cues that conflict with the serial-ordering process deployed to perform the serial recall task. In this view, the post-categorical properties (e.g., phonology, meaning) of speech play no role. The present study reassessed the implications of recent demonstrations of auditory post-categorical distraction in serial recall that have been taken as support for an alternative, attentional-diversion, account of the irrelevant speech effect. Focusing on the disruptive effect of emotionally valent compared to neutral words on serial recall, we show that the distracter-valence effect is eliminated under conditions—high task-encoding load—thought to shield against attentional diversion whereas the general effect of speech (neutral words compared to quiet) remains unaffected (Experiment 1). Furthermore, the distracter-valence effect generalizes to a task that does not require the processing of serial order—the missing-item task—while the effect of speech per se is attenuated in this task (Experiment 2). We conclude that post-categorical auditory distraction phenomena in serial short-term memory are incidental: they are observable in such a setting but, unlike the acoustically driven irrelevant speech effect, are not integral to it. As such, the findings support a duplex-mechanism account over a unitary view of auditory distraction.