| Sumario: | In free visual search, individuals move their eyes around a scene and search for targets with a "functional visual field" (FVF) surrounding the current point of fixation. Items could be sampled in series, one after the other within the FVF or the entire FVF might be processed in parallel. In either case, processing could be uniform, on average, across the FVF or, alternatively, some items or regions in the FVF might be systematically processed more successfully than others. To assess this, we had observers fixate at a point and then flashed a ring of eight items around fixation. We examined the distribution of errors as a function of the angular position around fixation. We found, as might be expected, that, on average, fewer errors were made on the horizontal than on the vertical meridian. Interestingly, we found reliable, idiosyncratic deviations from this average pattern. Observers tended to have specific angular positions that were consistently better or worse than average. These biases in search performance might be related to the production of otherwise apparently random false negative errors in visual search. Public Significance Statement: Under most circumstances, when an observer is search for a visual target, they will move their eyes around the visual field and, during each fixation, they will process visual stimuli within a "functional visual field" (FVF) surrounding that current point of fixation. It is usually assumed that processing within that FVF is roughly uniform. If one assumes that items are selected in series within the FVF, that would mean that one item in the FVF is no more likely to be selected than another. If one assumes that the entire FVF is processed in parallel, that would mean that processing would be equivalent at all locations. The results present here show that this is not true. Faced with a ring of stimuli around fixation, observers preferentially process some over others. Moreover, these preferences are idiosyncratic, varying reliably from observer to observer.
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