The Gollin test and the optical properties of incomplete figures at threshold

The Gollin test is a developmental test for measuring visual perceptual skills (Gollin, 1960 Perceptual and Motor Skills 11 289 - 298). The aim of our work was to measure the thresholds of recognition of incomplete figures when presented for the first time to observers, and relate this to their contour lengths and 2-D Fourier spectra. We generated 73 contour images of familiar objects. They were presented as incomplete figures, beginning from 0% of contour to 100% via the random addition of small fragments. The observers' task was to recognise figures as quickly as possible. Their score was the percentage of contour displayed at the moment of recognition. We found that the value of the threshold, in terms of percentage of contour length displayed, was similar for all images, averaging 12%, irrespective of the total length of contour of the full figure. For both complete and incomplete figures at threshold we carried out 2-D Fourier transform analysis, measuring the centroids of their spectra. The energy spectrum of each figure was transformed into an averaged amplitude spatial-frequency profile, representing the total energy within each of three orientation profiles, and the centroid was then calculated. We found that the value of the centroid at threshold was similar across the figures employed, averaging 6.3 cycles deg-1. We showed that the centroid of the amplitude spatial-frequency spectrum of an image coincides with the maximum on the curve of human contrast sensitivity.

European Conference on Visual Perception.
Kusadasi, Turkey
26-30 Aug, 2001.
Supplement, ECVP 2001, Abstract