Academic journal article The Psychological Record

Stimulus Equivalence in the Tactile Modality

Academic journal article The Psychological Record

Stimulus Equivalence in the Tactile Modality

Article excerpt

In studies of stimulus equivalence subjects learn sets of conditional discriminations. Subsequent tests show that the conditionally related stimuli form equivalence classes (cf., Dube, Green, & Serna, 1993; Lynch & Green, 1991; Sidman, 1971; Sidman & Tailby, 1982; Wetherby, Karlan, & Spradlin, 1983). These studies have employed auditory and visual stimuli and have demonstrated equivalence classes of solely auditory, solely visual, and bimodal stimuli.

Bush (1993) extended previous work on stimulus equivalence by including tactile stimuli in order to examine cross-modal transfer (learning that transfers from one sensory modality to another) of equivalence relations. Her work demonstrated that multimodal classes of auditory, visual, and tactile stimuli emerge from conditional discriminations taught in two modalities. However, the study did not attempt to determine whether or not equivalence classes would emerge if only tactile stimuli were used.

Although the subjects in Bush's (1993) study demonstrated equivalence, they experienced some difficulty with the conditional discriminations that had both tactile samples and tactile comparisons. This finding is consistent with the equivocal results of most psychologists who include tactile matching-to-sample comparisons in sensory training (cf., Cronin, 1973; Ettlinger, 1977; Jones & Robinson, 1973; Millar, 1971; Solso & Raynis, 1982).

The difficulty that Bush's subjects experienced on trials with tactile samples and comparisons, coupled with past difficulties in generating accurate performances on tactile matching-to-sample tasks, suggests the importance of testing for the emergence of equivalence classes when tactile stimuli are used exclusively. The present study used well-developed procedures from stimulus equivalence research (Sidman & Tailby, 1982) to determine if equivalence classes would emerge for three-dimensional objects.



Three 6- and 7-year-olds recruited by a newspaper advertisement served as subjects. Subject LMI (female) received 18 teaching sessions and 5 testing sessions; Subject BDX (male) received 15 teaching sessions and 5 testing sessions; and Subject TFX (female) had 19 teaching sessions and 5 testing sessions. All three of the children were in first grade. The children's parents received $3.00 for each session the child attended.


A black screening box (32 cm wide, 47 cm long, and 26 cm high) with a horizontal, middle division shielded the experimental objects. An old sweatshirt was attached to the box opening so that subjects could place both hands inside the box simultaneously to handle the stimuli without being able to see them. (The neck of the sweatshirt was sewn shut, so subjects were unable to see the stimuli. Subjects placed their arms inside the sleeves of the sweatshirt so they could feel the stimuli. [ILLUSTRATION FOR FIGURE 1 OMITTED].)

The average size of the nine tactile stimuli was 2.83 cm wide, 7.28 cm long, and 2.64 cm high. All stimuli used were approximately the same size. These stimuli were A1 = hair band, A2 = flat paper clip, A3 = nail polish bottle, B1 = wire hair roller, B2 = porcelain napkin holder, B3 = cable tv part, C1 = broken freezer knob, C2 = rose tube, and C3 = office binder. All of these objects were carefully chosen over the summer by working with two pilot children (one male and one female) aged 6 and 7, respectively. These children, blindfolded, were presented with numerous objects to feel. While feeling each object, the children were asked what the object was, what it felt like, and what they would call it. The final nine objects were selected because the pilot children could not name, identify, or create any verbal association with the objects.

The sample stimulus was always presented in a bowl which was attached to a tray on the top half of the box, and the three comparisons were presented in three specific stationary dishes attached to a tray on the bottom level of the screening box. …

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