DECREASING ERRORS IN READING‐RELATED MATCHING TO SAMPLE USING A DELAYED‐SAMPLE PROCEDURE

Two men with intellectual disabilities initially demonstrated intermediate accuracy in two‐choice matching‐to‐sample (MTS) procedures. A printed‐letter identity MTS procedure was used with 1 participant, and a spoken‐to‐printed‐word MTS procedure was used with the other participant. Errors decreased substantially under a delayed‐sample procedure, in which the choice stimuli were presented first and the sample was presented only after 5 s without a response to the choice stimuli.     

A RESPONSE-RESTRICTION ANALYSIS OF STEREOTYPY IN ADOLESCENTS WITH MENTAL RETARDATION: IMPLICATIONS FOR APPLIED BEHAVIOR ANALYSIS

The behavior of 4 adolescents with severe or profound mental retardation was evaluated in the presence of four sets of materials during periods of unstructured leisure activity. Functional engagement with the materials, stereotypic engagement with the materials, stereotypy without interaction with the materials, and other aberrant behaviors were recorded. Across a series of experimental conditions, the number of sets of materials was reduced from four to one by eliminating the set most frequently manipulated in each preceding condition. In the final condition, four sets of materials were again made available for manipulation. The procedures replicated Green and Striefel's (1988) response-restriction analysis of the activity preferences and play behaviors of children with autism. In general, the results of the present experiment replicate those of Green and Striefel in that reallocation of responding was idiosyncratic and unpredictable as sets of materials were removed. Nevertheless, the results provided insight into how responding might be reallocated if it were restricted through behavioral interventions rather than by restriction of access. Thus, the results are discussed with respect to how response-restriction analyses may be useful in identifying topographies of behavior that could be included in differential reinforcement contingencies that are designed to affect stereotypic behavior and in the selection and arrangement of environmental stimuli to minimize the presence of evokers of stereotypy.     

Differential effects of red and blue coloured lighting on gambling behaviour

Gambling at a modified version of three-card brag was observed for 28 volunteers, subjected to red or blue light conditions. It is concluded that subjects within a red light environment gambled more money more often and selected riskier odds than did subjects gambling under blue light. Furthermore, riskier bets were generally associated with later trials and red light again enhanced such an effect as compared with blue light. The results are discussed in terms of psychoanalytical theory, psychophysiology and choice shifts within group situations for various gambling activities.     

Establishing auditory stimulus control over an eight-member equivalence class via conditional discrimination procedures

Two eight-member equivalence classes of visual stimuli were established during three phases of a training program. In Phase 1, two training arrangements were compared. In one, 3 subjects were taught on different trials to select from a single pair of comparison stimuli (A1, A2) in response to eight sample stimuli that were trained in pairs (B1, B2; C1, C2; D1, D2; E1, E2). In the second arrangement, subjects were taught to select from four pairs of comparisons (B1, B2; C1, C2; D3, D2; E2, E2) in response to two samples (A1, A2). Training with the single pair of comparison stimuli resulted in the development of equivalence relations (B1C1, B2C2, D1B1, D2B2, B1E1, B2E2, C1D1, C2D2, C1E1, C2E2, D1E1, D2E2, and their reciprocals) between the sample stimuli without direct training of these relations. In the other training arrangement, these relations among the comparison stimuli developed in the performance of 1 subject only. In Phase 2, three new pairs of stimuli (F1, F2; G1, G2; H1, H2) were substituted for three of the original pairs (B1, B2; C1, C2; D1, D2) and the training arrangements for the groups were reversed. Following training, the performances that showed equivalence relations on the probes in the first phase also showed equivalence relations in the second phase. If such relations did not develop in the first phase, they did not do so in the second phase. In Phase 3, relations between stimuli across the two previous phases (e.g., B1F1, B2F2, B1G1, B2H2, C1F1, etc.) were investigated. The 4 subjects whose performances showed the development of these relations were taught to select one stimulus from each class (E1 and E2) in response to a verbal label (I1 and I2) and then were tested to see if the verbal label controlled responding to the remaining members of the class (e.g., I1A1, I2A2, I1B1, I2B2, etc.). For 3 subjects, this generalized control occurred; for the 4th, generalization occurred only after verbal training with a second pair of visual stimuli (F1 and F2). In retests several months later, these auditory-visual relations were found to be intact or, if not, were recovered without direct training.     

The merger and development of equivalence classes by unreinforced conditional selection of comparison stimuli

Three experiments assessed the likelihood that subjects with histories of equivalence class development would respond conditionally on new discriminations in the absence of differential consequences for responses. In the first two experiments, two groups of subjects with different experimental histories, but whose performances showed four equivalence classes, responded on trials without explicit reinforcement involving samples from two of the classes and comparisons from the other two classes, in a two-choice matching-to-sample format. Subjects consistently selected a particular comparison in the presence of a particular sample. Subsequent tests showed the emergence of equivalence relations between stimuli from classes linked by the unreinforced conditional selections. Subsequently, in Experiment II, the subjects' responses in the conditional selection trials were reinforced if the selection was reversed from that made previously. Although reversed selection was maintained, 2 of the 3 subjects continued to perform on equivalence relation trials according to their original unreinforced selections. In the third experiment, these 2 subjects responded on a series of conditional discriminations involving three new pairs of sample stimuli and one new pair of comparison stimuli. No explicit reinforcement followed responses on any trial in this experiment. Subsequent tests for equivalence between sample stimuli revealed the development of two equivalence classes.     

Frequency selectivity in the parakeet (Melopsittacus undulatus) studied with psychophysical tuning curves

Seven parakeets were trained to avoid shock during pure-tone stimulation. A modified method of limits was used to measure detection thresholds of the pure tones. The intensity of masker tones, at numerous frequencies, was varied in order to measure the masked threshold of a probe-tone signal set at a fixed frequency and intensity. Masking curves were obtained for three probe tones (.63, 1.6, and 2.5 kHz) at each of five sensation levels (10, 20, 30, 40, and 50 dB). The masking curves from this procedure are frequently referred to as "psychophysical tuning curves" and provide an indication of frequency selectivity. The results are compared with analogous data in other species and suggest that frequency analysis in the parakeet ear is somewhat less accurate than in the mammalian ear.