Maintaining a continuous, stable perception of the visual world relies on the ability to integrate information from previous fixations with the current one. An essential component of this integration is trans-saccadic memory (TSM), memory for information across saccades. TSM capacity may play a limiting role in tasks requiring efficient trans-saccadic integration, such as multiple-fixation visual search tasks. We estimated TSM capacity and investigated its relationship to visual short-term memory (VSTM) using two visual search tasks, one in which participants maintained fixation while saccades were simulated and another where participants made a sequence of actual saccades. We derived a memory-limited ideal observer model to estimate lower-bounds on memory capacities from human search performance. Analysis of the single-fixation search task resulted in capacity estimates (4-8 bits) consistent with those reported for traditional VSTM tasks. However, analysis of the multiple-fixation search task resulted in capacity estimates (15-32 bits) significantly larger than those measured for VSTM. Our results suggest that TSM plays an important role in visual search tasks, that the effective capacity of TSM is greater than or equal to that of VSTM, and that the TSM capacity of human observers significantly limits performance in multiple-fixation visual search tasks. (PsycINFO Database Record
Angular path integration refers to the ability to maintain an estimate of self-location after a rotational displacement by integrating internally-generated (idiothetic) self-motion signals over time. Previous work has found that non-sensory inputs, namely spatial memory, can play a powerful role in angular path integration (Arthur et al., 2007, 2009). Here we investigated the conditions under which spatial memory facilitates angular path integration. We hypothesized that the benefit of spatial memory is particularly likely in spatial updating tasks in which one’s self-location estimate is referenced to external space. To test this idea, we administered passive, nonvisual body rotations (ranging 40° – 140°) about the yaw axis and asked participants to use verbal reports or open-loop manual pointing to indicate the magnitude of the rotation. Prior to some trials, previews of the surrounding environment were given. We found that when participants adopted an egocentric frame of reference, the previously-observed benefit of previews on within-subject response precision was not manifested, regardless of whether remembered spatial frameworks were derived from vision or spatial language. We conclude that the powerful effect of spatial memory is dependent on one’s frame of reference during self-motion updating.
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