Abstract
An important factor determining visual short-term memory (VSTM) capacity is the efficiency with which people can avoid encoding irrelevant information (Vogel, McCollough, & Machizawa, 2005). We investigated the impact of emotion on VSTM and whether it depends on the degree to which selective attention is required at encoding. In two experiments, emotional distraction — induced via presentations of task-irrelevant emotional versus neutral pictures — impaired VSTM primarily when successful performance entailed the parsing of relevant from irrelevant information. This selective effect emerged even though emotional distractors were presented only after an encoding display had come and gone. In Experiment 1, participants performed a change detection task on three black shapes, which either appeared alone or were accompanied in the pre-change display by three gray non-targets (the post-change display contained only the black shapes). On each trial, the pre-change display appeared for 150-ms, followed by a 900-ms ISI and then the post-change display. On one-third of the trials, an emotional picture appeared briefly during the ISI, and on one-third a neutral picture appeared briefly. An emotion-induced VSTM impairment occurred only when participants had been required to ignore irrelevant non-targets. Experiment 2 controlled for the number of items presented in the two conditions: either two targets and two non-targets appeared in the encoding display or four targets appeared alone. Again, emotional distractors impaired VSTM primarily when non-targets had been present. These emotion-induced effects were strongest when the picture appeared sooner rather than later after the offset of the encoding array; thus, the impact of emotional distractors on VSTM depends both on the degree to which VSTM encoding requires selective attention and on when such distractors appear. The temporal dynamics suggest that emotional distraction may impede the selective discarding of irrelevant items during VSTM consolidation.