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Sharmini Atputharaj, David Cappadocia, J. Crawford; Memory-guided saccades to visual stimulus sequences: influence of set-size and spatiotemporal structure on recall accuracy. Journal of Vision 2018;18(10):1013. doi: https://doi.org/10.1167/18.10.1013.
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© ARVO (1962-2015); The Authors (2016-present)
Saccades have been used extensively as a tool to measure cognitive processes such as visual working memory (VWM). The goal of this study was to identify the effect of spatiotemporal structure on performance in memory-guided saccade sequences. Six participants (ages 21-34) were presented with a sequence of targets on a 5x5 LED display encompassing 20°x20° of visual space, then they were told to fixate the central LED and memorize a sequence of 3-6 targets presented peripherally. The spatiotemporal structure of this sequence could be (1)structured (recognizable shape and temporal order), (2)semi-structured (recognizable shape with random temporal order) or (3)unstructured (random shape, random temporal order). Following offset of the fixation light, subjects saccade toward the remembered spatiotemporal sequence of targets. Presentation and execution of saccades were in complete darkness. ANOVA results showed significant main effects: 1)saccade errors were greatest for unstructured conditions and 2)targets presented earlier in sequence were recalled with higher accuracy than later targets. There were also interactions between spatiotemporal structure and 1)set-size (structure provided greater benefits for larger set-sizes) and 2)order (structure provided more benefits for early targets). However, in this experiment it was difficult to disentangle errors of target choice, errors of target position memory, and saccade motor errors. Therefore, in Experiment 2, we added a continuously-displayed placeholder array outlining the 25 possible target locations, thus providing additional allocentric cues for target selection in the recall/motor execution phase. Preliminary results (n=4) for Experiment 2 show similar trends with respect to the effect of spatiotemporal structure, however, the presence of allocentric cues seems to greatly improve the recall accuracy compared to Experiment 1. Overall, these results show that VWM capacity is improved by the presence of spatiotemporal structure for sequences that had egocentric and allocentric spatial representation, but that this interacts with other factors such as set-size.
Meeting abstract presented at VSS 2018
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