The Gap Effect: Chromatic and Achromatic Visual Discrimination as Affected by Field Separation

The effect upon visual discrimination of slightly separating the fields to be compared was tested for three conditions. Luminance discrimination was impaired, but chromatic discriminations were either unaffected or improved, depending upon the colours used. The results are explained in terms of three factors (distance, contour enhancement, averaging), two of which can be expected to behave differentially, depending upon the nature of the discrimination.