DOI: 10.6078/d18t35
title: Data from: Idiosyncratic perception: a link between acuity, perceived position and apparent size

description: Perceiving the positions of objects is a prerequisite for most other
 visual and visuomotor functions, but human perception of object position
 varies from one individual to the next. The source of these individual
 differences in perceived position and their perceptual consequences are
 unknown. Here, we tested whether idiosyncratic biases in the underlying
 representation of visual space propagate across different levels of visual
 processing. In Experiment 1, using a position matching task, we found
 stable, observer-specific compressions and expansions within local regions
 throughout the visual field. We then measured Vernier acuity (Experiment
 2) and perceived size of objects (Experiment 3) across the visual field
 and found that individualized spatial distortions were closely associated
 with variations in both visual acuity and apparent object size. Our
 results reveal idiosyncratic biases in perceived position and size,
 originating from a heterogeneous spatial resolution that carries across
 the visual hierarchy.
description: 1) Spatial localization biases dataset: Collected from nine
 observers on 6 separate sessions. Observers matched the location of the
 cursor to a previous briefly presented noise patch stimulus. There were 5
 possible eccentricities on which the noise patch (i.e., the target) was
 presented. On each eccentricity, there were 48 possibble angular
 locations, resulting in a total of 240 possible locations. The x-y
 coordinates of the reported locations were recored and then each reported
 x-y coordinate was transformed into polar angle. 2)
 Vernier acuity dataset: 7 observers who participated in the spatial
 localization task participated in this experiment. Vernier acuity was
 tested on 8 equidistant locations on the eccentricity of 6 degrees of
 visual angles. On each trial, participants responded by either pressing
 left key or right key to indicate the spatial relationship of two lines
 that were spatially misalligned. To analyze the data, for every Vernier
 misalignment at a given location, we calculated the proportions in which
 observers reported that the outer line was shifted more clockwise than the
 inner line. Then we fitted the proportion of clockwise responses with a
 logistic function using a least-squares procedure. The just-noticeable
 difference (JND) was estimated by taking half of the distance between the
 Vernier misalignments that gave 25% and 75% clockwise responses on the
 best-fit logistic function. 3) Perceived size dataset:
 3 observers who participated in the previous experiments participated in
 this experiment. On each trial, an arc was presented at one of the 20
 locations separated by 18° at an eccentricity of 6 d.v.a.. Upon the offset
 of the arc, observers responded whether it was shorter or longer than the
 average. There were six different possible lengths and the mean length
 (never shown in the experiment) was 15°. To estimate the perceived size of
 the arc at each location, we calculated the proportion of trials in which
 the observer responded “longer than average” for each length of the arc.
 Then these proportions were fitted to a logistic function using a
 least-squares procedure. The point of subjective equality (PSE), which
 represents the perceived set mean, was defined as the arc length at which
 the proportion of “longer” responses was 50% on the best-fit logistic
 function.