Perceptual classes established with forced-choice primary general ration tests and transfer of function

In Experiment 1, 20 college students learned two identity conditional discr iminations using squares that differed in interior-fill percentage (called Fill23 and Fill77). A two-choice generalization test was then presented wit h number of test trials varied across groups of subjects. The test samples were 19 squares that ranged in fill value front 23% to 77%; the comparisons were squares with Fill23 and Fill77. The resulting gradients did not vary as a function of number of test trials. When the generalization test was re peated with a third comparison, "neither," the ranges of fill values that o ccasioned the exclusive selection of Fill23 or Fill77 were direct functions of the number of prior two-choice generalization trials. Finally, a discri minability test revealed that Fill23 and Fill77 were discriminable from the intermediate fill values. In Experiment 2, perceptual classes were establi shed with 5 new students using 760 forced-choice generalization test trials . The students were then trained to select a different glyph in the presenc e of Fill23 and Fill77, followed by a three-choice generalization test in w hich the 19 fill stimuli served as samples and the two glyphs served as com parisons. The gradients overlapped with those previously obtained during th e three-choice generalization test that used Fill23 and Fill77 its comparis ons. Finally, a discriminability test showed that many adjacent stimuli alo ng the fill dimension were discriminable from each other. Together, the res ults of both experiments suggest that ranges of fill-based stimuli function ed as members of perceptual classes, and each class also functioned as it t ransfer network for a new selection-based response.