We estimated the discrimination thresholds for each prototype from the last five reversals of the staircase and averaged the discrimination thresholds within subject across the two experimental runs.
In the baseline runs, discrimination thresholds were measured without adaptation to shape.
Independent t-tests investigated whether groups differed if force discrimination thresholds.
These data suggest that perceptual anchoring matures prior to the attainment of adult-like discrimination thresholds.
The spread parameter was varied to measure form discrimination thresholds for simple geometrical shapes.
The duration of the comparison interval was always longer but varied adaptively to determine discrimination thresholds.
Adaptation improved discrimination thresholds, evidenced by a main effect of adaptation condition (F 1, 77) = 58.5, p < 0.001; Fig. 2a).
To measure shape discrimination thresholds, we constructed a parametric shape space with ShapeToolbox48 (URL: http://github.com/saarela/ShapeToolbox).
Measured frequency discrimination thresholds from 3 animals at 3 different reference frequencies were comparable with previously published results.
We note that the stronger decorrelation observed for shape class B is consistent with the larger decrease in perceptual discrimination thresholds for these stimuli reported above.
We then asked if perceptual adaptation to stimuli from one of the shape classes would improve subsequent shape discrimination thresholds for items from that same class.
