Content area
Full text
Research on stimulus equivalence and stimulus class formation has shown that after being trained on multiple conditional discriminations, verbally capable humans as young as 2 years of age typically match all directly and indirectly linked stimuli and stimulus elements to one another irrespective of whether they are used as samples or as comparisons (Barnes, McCullagh, & Keenan, 1990; Devany, Hayes,
Nelson, 1986; Eikeseth & Smith, 1992; Saunders, Saunders, Kirby, & Spradlin, 1988; Schenk, 1993; Spradlin, Cotter, & Baxley, 1973; Stromer & Mackay, 1992, 1993; Stromer & Stromer, 1990a, 1990b). For example, in the study by Stromer and Stromer (1990a), 18 college students were trained on arbitrary matching tasks with two-element complex stimuli (AB and AC) as samples and single-element stimuli (D and E) as comparisons (A1B1-D1, A2B2-D2, A1C1-E1, A2C2-E2). Subsequent probes revealed that most students matched all directly related (A-B, A-C, A-D, A-E, B-D, C-E) and indirectly related stimulus elements (B-C, BE, C-D, and D-E) to one another, regardless of whether they were used as samples or as comparisons.
Some of these studies also showed that existing arbitrary stimulus relations can be extended via elements of complex stimuli under testing conditions (Schenk, 1993; Stromer & Stromer, 1990a, 1990b). For example, in the study by Stromer and Stromer (1990a), subjects who demonstrated the aforementioned equivalence relations also received an AF-B task under test conditions (no programmed consequences). Subsequent probes revealed that, among other findings, the subjects related the F stimuli to the A and B stimuli (A-F, F-A, B-F, F-B). Similar findings with preschool children were reported by Schenk (1993). After obtaining A-B and B-A relations from training on an identity task with complex stimuli, AB-AB, Schenk presented the A-B test again but with new stimuli (C) added to the samples (AC-B) or to the comparisons (A-CB). Subsequent probes revealed that, as a result of this exposure, the children related the C stimuli to the A and B stimuli (A-C, C-A, B-C, C-B).
Recently, Smeets and Striefel (1994) examined whether transfer from identity to arbitrary matching tasks can be accomplished through exposure to complex stimuli under nonreinforced conditions. After being trained on an identity task with colors (C; green and yellow) as samples and as comparisons (C-C task), preschool children received a series of tests (no...