Academic journal article The Psychological Record

The Generalization of Emergent Relations in Equivalence Classes: Stimulus Substitutability

Academic journal article The Psychological Record

The Generalization of Emergent Relations in Equivalence Classes: Stimulus Substitutability

Article excerpt

An equivalence class is a group of stimuli that become related to each other even though they do not resemble one another (Sidman, 1971). The written words CHIEN, DOG, and PERRO and the "picture of a dalmatian" can be established as a 4-member equivalence class by training three pairs, such as CHIEN-DOG, DOG-PERRO, and PERRO-"picture of a dalmatian." A 4-member equivalence class contains 16 stimulus-stimulus relations, three of which are established by training; the remaining 13 stimulus-stimulus pairs are presented as emergent relations tests to assess class formation (Fields, Adams, Newman, & Verhave, 1992; Fields & Verhave, 1987). If a person identifies the relatedness of the stimuli in each test pair, all of the stimuli are related to each other and an equivalence class has been formed (Fields & Verhave, 1987; Fields, Verhave, & Fath, 1984; Sidman & Tailby, 1982). Different test pairs assess reflexivity (e.g., CHIEN-CHIEN), symmetry (e.g., DOG-CHIEN), transitivity (e.g., DOG-"picture of a dalmatian"), and equivalence or symmetry and transitivity in combination (e.g.,"picture of a dalmatian"-CHIEN) (Bush, Sidman, & de Rose, 1989; Fields & Verhave, 1987; Fields et al., 1992). When all of the emergent relations tests are passed, the stimuli function as an equivalence class.

In natural settings, stimuli have a range of variation. Thus, because the picture of a dalmatian is a member of the class of dog-words, would a picture of a beagle become related to DOG, CHIEN, and PERRO? This possibility can be assessed by conducting generalization tests for all emergent relations. For example, a generalization test of equivalence would include the "picture of a beagie" as a sample with CHIEN as a comparison. The likelihood of choosing CHIEN would index the relatedness of the new picture to the class member.

Fields, Reeve, Adams, and Verhave (1991) demonstrated the generalization of the equivalence relation in a 3-member class. In the present study we assessed whether novel stimuli that resemble one member of a class became related to all of the members of a 4-member equivalence class. In addition, the similarity of the different generalization gradients were used to evaluate the substitutability of the stimuli in the equivalence class.

Experiment 1

Method

Subjects

Six undergraduate students at Queens College/CUNY were recruited from an introductory psychology class. No subject had any prior familiarity with the research. Each subject received partial course credit for completing the experiment. Credit did not depend on performance. Completion of the experiment required five or six sessions scheduled over a 3-week period. Each session lasted for 1-1.5 hr.

Apparatus and Stimuli

Experimental stimuli were presented on a monochrome computer monitor. Subjects were seated in a cubicle at a table facing the microcomputer. Responses consisted of touching specific keys on the computer keyboard and were recorded by the computer. The experiment was conducted using software specifically developed for the study equivalence classes.

Each of the two classes was composed of three nonsense syllables and a group of lines. In Class 1, the nonsense syllables were LEQ (A1), HUK (B1), and POV (C1); in Class 2, the nonsense syllables were MEV (A2), GUQ (B2), and ZOJ (C2). The lines were composed of contiguous horizontal strings of ASCII Character 177 ([176]) and were identified according to the number of ASCII characters in the line. Each ([176]) was 3 mm wide and 5 mm high on the computer screen. The D stimuli used for training were designated by class and length. For example, the D stimulus in Class 1 was 1 unit long and was designated D1(1) where the numeral after D identified class membership and the numeral between the parentheses refers to line length. Likewise, the D stimulus in Class 2 was 25 units long and was designated D2(25). …

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