PERCEPTUAL CLASSES ESTABLISHED WITH FORCED‐CHOICE PRIMARY GENERALIZATION TESTS AND TRANSFER OF FUNCTION

In Experiment 1, 20 college students learned two identity conditional discriminations using squares that differed in interior‐fill percentage (called Fill23 and Fill77). A two‐choice generalization test was then presented with number of test trials varied across groups of subjects. The test samples were 19 squares that ranged in fill value from 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 repeated with a third comparison, “neither,” the ranges of fill values that occasioned the exclusive selection of Fill23 or Fill77 were direct functions of the number of prior two‐choice generalization trials. Finally, a discriminability test revealed that Fill23 and Fill77 were discriminable from the intermediate fill values. In Experiment 2, perceptual classes were established with 5 new students using 760 forced‐choice generalization test trials. The students were then trained to select a different glyph in the presence of Fill23 and Fill77, followed by a three‐choice generalization test in which the 19 fill stimuli served as samples and the two glyphs served as comparisons. The gradients overlapped with those previously obtained during the three‐choice generalization test that used Fill23 and Fill77 as comparisons. Finally, a discriminability test showed that many adjacent stimuli along the fill dimension were discriminable from each other. Together, the results of both experiments suggest that ranges of fill‐based stimuli functioned as members of perceptual classes, and each class also functioned as a transfer network for a new selection‐based response.