Academic journal article The Psychological Record

Simple Successive Discrimination and Functional Class Formation in Preschool Children

Academic journal article The Psychological Record

Simple Successive Discrimination and Functional Class Formation in Preschool Children

Article excerpt

Responding under the control of arbitrarily related stimulus classes has been widely studied from the perspective of the stimulus equivalence descriptive model (Sidman, 1994). Equivalence relations can be established by conditional discrimination (four-term contingency) training using the arbitrary matching-to-sample procedure and assessed by tests of emergent conditional relations according to the defining properties of equivalence relations (i.e., reflexivity, symmetry, and transitivity; Sidman & Tailby, 1982).

Grouping stimuli into classes or categories is a basic and essential process in learning complex repertoires, such as abstraction, concept formation, symbolic representation, and meaning relations (de Rose, 1993; Sidman, 1994; Sidman & Tailby, 1982). Thus, the stimulus equivalence descriptive model permits the objective and systematic study of symbolic behavior.

An alternative approach to the study of stimulus class formation is through the mathematical definition of partition, referring to a division of a set into two or more disjointed subsets, in which the elements of each subset are equivalent to each other (Vaughan, 1988). The union of all subsets is equal to the universal set, and the intersection is an empty set.

In a study by Vaughan (1988), pigeons were exposed to a simple successive (go/no-go) discrimination reversal procedure. The experimental box was adapted for the presentation of slides in a central key. A set of 40 slides was randomly divided into two subsets, with 20 slides in each subset. In the initial condition, Set I was correlated with reinforcement ([S.sup.+]), and Set 2 was correlated with extinction ([S.sup.-]), in which key pecking only produced food contingent upon the presence of any [S.sup.+] stimulus projected on the key. Each session had 80 trials, with two trials for each stimulus, and the stimuli were presented in a random order across the trials. When the subject's performance reached the learning criterion (i.e., responding in the presence of all 20 [S.sup.+] and not responding in the presence of all 20 [S.sup.-]), a systematic contingency reversal program began. At each reversal, the stimuli defined as [S.sup.+] in the previous condition changed to [S.sup.+], and those defined as [S.sup.+] changed to [S.sup.+]. Throughout the successive contingency reversal training, responding according to the current contingency gradually occurred earlier than in the previous reversals. In other words, after each reversal, the consequences for responding in the presence of a few stimuli in a particular set were sufficient to change the performance in response to the other stimuli in the same set before the pigeons experienced the reversed contingencies for all of the stimuli in each set. This increasingly proficient performance with repeated training exposure has some similar features to what Harlow (1949) called a learning set.

Since the original study by Vaughan (1988), other studies have used the simple discrimination reversal procedure with several populations, including adults and adolescents diagnosed with intellectual disability (Sidman, Wynne, Maguire, & Barnes, 1989), typically developing children and children diagnosed with autism (Lionello-DeNolf, McIlvane, Canovas, de Souza, & Barros, 2008), rats (Dube, Callahan, & McIlvane, 1993), capuchin monkeys (Barros, de Souza, & Costa, in press; Goulart, Galvao, & Barros, 2003), and sea lions (Kastak, Shusterman, & Kastak, 2001). Altogether, the results were positive, although some intersubject variability was found, suggesting that the procedure developed by Vaughan (1988) is appropriate to study stimulus class formation.

Dube et al. (1993) introduced an ingenious procedure to probe for functional class formation in the repeated reversal procedure. A reversal begins with some, but not all, of the stimuli. After the criterion of reversed performance is reached, the stimuli that were "saved" for the probes are introduced, and responding to them indicates whether the subjects are responding according to pre- or post-reversal contingencies. …

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