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Brendon B. Hsieh, David E. Irwin; Center blocks the square: Eye movements to absent objects are under cognitive control. Journal of Vision 2005;5(8):437. doi: 10.1167/5.8.437.
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© ARVO (1962-2015); The Authors (2016-present)
Are eye movements to the former locations of objects in space reflective of memory retrieval processes that index space during memory encoding? While refixations to the former locations of objects have been found in previous studies using semantic verification tasks (e.g., Spivey & Richardson, Cognition, 2000), we hypothesized that the visuospatial disruption that eye movements cause might reduce refixations to the former locations of objects in visuospatial memory tasks. To test this, subjects were visually presented 4 numbers arrayed in the corners of a 3x3 grid. The numbers were presented serially and the subject fixated each one and then returned their gaze to the center of the empty grid at which point their memory for the numbers was assessed in one of several ways (varied across experiments). In experiment 1, subjects were presented an audio number probe and they responded whether the number had been present or absent in the grid. No eye movements to the former location of the number were found. In experiment 2, subjects verified the spatial position of the audio number probe. A small number of saccades were made to the former location of the number, but substantially fewer than reported in previous studies. In the third experiment subjects reported the three locations of the numbers that would add up to the audio number probe. A slight increase in saccades to the relevant locations was observed, but again not at the levels reported by Richardson and Spivey (2000). In all three experiments subjects preferred to keep their eyes still while performing the memory task. Furthermore, most saccades to relevant locations were made after the memory response, suggesting that they reflect post-response verification rather than memory retrieval. These results suggest that oculomotor spatial indices are not necessarily encoded and activated during memory retrieval, especially under conditions in which eye movements might interfere with cognitive processing.
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