Competitive interactions automatically compromise visual working memory.
Ahmad J., Nobre A., Shapiro K., McNab F.
Competition between visually presented stimuli is associated with longer reaction times, reduced BOLD response and reduced neural firing. Previously we observed that competition affects working memory (WM) performance (Ahmad, Nobre, Shapiro & McNab, submitted). In that study we manipulated competition during WM encoding by varying the spatial proximity between two items (Near vs. Far conditions). Participants were required to report the colour of a target item on a colour wheel. We demonstrated that the effect of competition extends to WM. Relative to the Far condition, the Near condition was associated with reduced WM precision and an increase in the number of times the colour of the un-cued item was erroneously reported. We also observed that pre-cues directing attention to one of the items failed to reduce the effects of competition on WM. Here we present an experiment in which we examined whether the effect of competition upon WM could be reduced with a different top-down manipulation. We examined whether prior knowledge of the trial type (Near vs. Far) would enable participants to reduce the effects of competition on WM. Prior knowledge was manipulated using a mixed versus blocked design. We again observed that the Far condition, relative to the Near condition, was associated with greater precision (F(1,27)= 24.12, p< .001) and a lower probability of reporting the colour of the non-target (F(1,27)= 66.13, p< .001). However, there was no interaction with prior knowledge for either precision (F(1,27)= 0.57, p=0.456) or probability of reporting the non-target (F(1,27)= 2.38, p=0.135). Together with the previous pre-cue experiment, the results indicate that it may not be possible to overcome the effects of competition on WM with top-down control. Meeting abstract presented at VSS 2015.