The Effect of Test Schedules on the Formation of Linked Perceptual Classes

Abstract

After training conditional discriminations among selected stimuli from two perceptual classes, the emergence of novel relations involving other members of both classes was assessed using cross-class probes. The cross-class probes were presented using one of four different testing schedules. In the 2/9 test, nine different probes were presented in each of two test blocks. In the 6/3 test, three different probes were presented in each of six test blocks. In the 18/1-RND test, each of the 18 cross-class probes was presented in separate test blocks. In the 2/9 and 6/3 tests, the cross-class probes were presented in a randomized order within test block. In the 18/1-RND test, the cross-class probes were presented in a randomized sequence. In the 18/1-PRGM test, however, the cross-class probes were presented in a programmed order (i.e., the values of the stimuli in each cross-class probe were changed systematically in the succession of probe presentations). About 55% of the linked perceptual classes emerged during the 2/9, 6/3, and 18/1-RND tests. Thus the number of different probes in a test block did not influence the emergence of classes as long as the probes were presented in a random order. Virtually all classes emerged during the 18/1-PRGM test. Thus at least one ordered introduction of different cross probes resulted in the reliable emergence of linked perceptual classes. Mechanisms responsible for linked perceptual class formation are discussed along with the relation of these classes to other complex categories.

Formation of Partially and Fully Elaborated Generalized Equivalence Classes

“…As the value of the anchor stimulus in each class was arbitrarily set to zero, the width of each class was indexed by the value of the boundary stimulus for that class. Previous research had shown that the value of the boundary stimulus in a perceptual class can vary as a function of whether it is used as a sample or as a comparison (Fields et al, 2002a;Fields et al, 2002b;Fields et al, 2005). In Phase 3, the values of the boundary stimuli when used as samples were determined using variant-to-base generalization tests, and the values of the boundary stimuli when used as comparisons were determined using base-to-variant generalization tests.…”

“…The 18 cross-class probes were presented in a systematic order-the 18/1 PRGM test (Fields et al, 2005). In this test, each of the probes (18) was presented in a separate test block (1) and the various probe types were introduced in a highly programmed progression (PRGM).…”

“…In this test, each of the probes (18) was presented in a separate test block (1) and the various probe types were introduced in a highly programmed progression (PRGM). Prior research has shown that its use maximizes the likelihood of forming linked perceptual classes (Fields et al, 2005). All nine A9-B9 probes were presented before the nine B9-A9 probes.…”

“…For a set of stimuli to act as a perceptual class, there should be generalization among the stimuli in a class, and some class members must be discriminable from each other (Fields et al, 2002b;Keller & Schoenfeld, 1950;Lashley & Wade, 1946;Lea, 1984;Wasserman et al, 1988). In this experiment, the discriminability of the stimuli in a perceptual class was measured by considering the response speeds occasioned by the anchor, midpoint and boundary stimuli (Fields et al, 2002b;Fields et al, 2005;Spencer & Chase, 1996). Response speed is the inverse of the latency that separated the onset of the set of comparison stimuli to the selection of one of the comparisons.…”

“…A medical example would be the tactile stimuli produced by a subdural tumor upon palpation (one perceptual class) and visual images of the tumor as they appear in a CT scan (the other perceptual class). The likelihood of forming a linked perceptual class is influenced by a variety of testing variables (Fields et al, 2005) and training variables . Linked perceptual classes also act as function transfer networks (Fields & Garruto, unpublished manuscript).…”