Irrelevant changing-state vibrotactile stimuli disrupt verbal serial recall: implications for theories of interference in short-term memory

What causes interference in short-term memory? We report the novel finding that immediate memory for visually-presented verbal items is sensitive to disruption from task-irrelevant vibrotactile stimuli. Specifically, short-term memory for a visual sequence is disrupted by a concurrently presented sequence of vibrations, but only when the vibrotactile sequence entails change (when the sequence "jumps" between the two hands). The impact on visual-verbal serial recall was similar in magnitude to that for auditory stimuli (Experiment 1). Performance of the missing item task, requiring recall of item-identity rather than item-order, was unaffected by changing-state vibrotactile stimuli (Experiment 2), as with changing-state auditory stimuli. Moreover, the predictability of the changing-state sequence did not modulate the magnitude of the effect, arguing against an attention-capture conceptualisation (Experiment 3). Results support the view that interference in short-term memory is produced by conflict between incompatible, amodal serial-ordering processes (interference-by-process) rather than interference between similar representational codes (interference-by-content).