Abstract
Spatial location is surely one of the most fundamental properties that is encoded in the mind. Yet it is striking how biases emerge even in the simplest spatial tasks we can imagine — e.g. when an observer must merely identify the location in which a stimulus appeared. When a dot appears momentarily in a shape, for example, subsequent localization responses are biased away from the shape's primary horizontal and vertical axes (so that, for example, a dot on one of the midlines is mislocalized as having been slightly off the midline). Such spatial biases are powerful (and are clearly visible to the naked eye in aggregated response plots), but also somewhat mysterious. In particular, their underlying nature remains uncertain. Are these biases of spatial memory? Of spatial perception? Of spatial responses? We addressed such challenges by looking for biases in tasks that minimize the demands of memory and perception. In a first study, observers completed a localization task, but one that minimized memory demands. Observers viewed two outlined shapes (e.g. circles) of different sizes, in different locations. A reference dot then appeared on each trial in one of the shapes. Observers' task was simply to place a response dot in the other shape, so that it was in the same relative location as the still-visible reference dot. Observers' responses were again biased away from the shape's horizontal and vertical axes. In a second study, we abandoned localization altogether. Observers completed an unrelated task, and entered their responses using a circular response wheel. The responses in this case were still biased away from the horizontal and vertical axes of the response space. Collectively these results suggest that spatial biases may be more general than has been previously supposed — reflecting not memory, but perception or action instead.
Meeting abstract presented at VSS 2018