Abstract: PURPOSE: Representations in focus of attention (FoA) of working memory (WM) have the highest activation state and processing privilege. Currently it has been claimed that there were two pathways for the representations entering FoA: external guidance and internal guidance. External guidance works on memorized stimuli at the encoding phase of WM, while internal guidance acts on representations stored in WM. Previous WM studies predominately addressed the two pathways separately. However, in daily cognitive processing, there are situations that the two pathways co-exist and may have distinct targets. Few studies have addressed the mechanism of competition between external and internal guidance when guiding the related target into FoA. The current study aimed at closing this gap.
METHODS: In a change detection task, we presented a set of memorized stimuli, which contains a color singleton serving as an external guidance. Additionally, we displayed a retro-cue in the maintenance phase of WM serving as an internal guidance. We examined whether the singleton effect could be modulated by the retro-cue. Experiment 1 investigated when a retro-cue started to take place in our task setting . Experiment 2 investigated the interaction between external and internal guidance when having distinct targets. Experiments 3 and 4 further examined this issue by enhancing the strength of internal guidance, tapping the processing time and validity of retro-cue, respectively.
RESULTS: We found that the singleton effect was modulated by the strength of the retro-cue: the singleton effect and retro-cue effect could co-exist when the strength of retro-cue was at a weak-to-medium level, yet the singleton effect diminished when the retro-cue was strong.
CONCLUSIONS: External and internal guidance competed for the limited resource, and the stronger one will guide the representation into FoA.

Key words: focus of attention, external guidance, internal guidance, working memory