Abstract: The present study examined the effects of dual task emphases on perceptual grouping processes in short-term memory. Two groups of 24 undergraduate students participated in the free recall and serial recall experiments. The memory materials were non-verbal visual spatial patterns. They were perceptually grouped by color into two types of memory list: the grouped list and ungrouped list. Subjects were asked to memorize all the items in a memory list first and then make a free recall or serial recall on an answer sheet. A concurrent tone-monitoring task was performed at either memory encoding or retrieval phase. There were three different types of dual-task instructions emphasizing the memory task, tone-monitoring task, and both separately. The results showed that the dual-task emphasis at encoding phase only affected the perceptual grouping process in free recall, not that in serial recall; while the dual-task emphasis at retrieval phase only affected the perceptual grouping process in serial recall, not that in free recall. The results suggest that the perceptual grouping processes in short-term memory might be under attentional control at both encoding and retrieval phases, but its locus and manifestation may vary with the type of memory task

Key words: short-term memory, perceptual grouping, dual task emphasis, attentional contro