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.     

Transfer of a conditional ordering response through conditional equivalence classes

Eight adult humans were taught conditional discriminations in a matching-to-sample format that led to the formation of two four-member equivalence classes. When subjects were taught to select one comparison stimulus from each class in a set order, they then ordered all other members of the equivalence classes without explicit training. When the ordering response itself was brought under conditional control, conditional sequencing also transferred to all other members of the two equivalence classes. When the conditional discriminations in the matching-to-sample task were brought under higher order conditional control, the eight stimulus members were arranged into four conditional equivalence classes. Both ordering and conditional ordering transferred to all members of the four conditional equivalence classes; for some subjects this occurred without a typical test for equivalence. One hundred twenty untrained sequences emerged from eight trained sequences for all subjects. Transfer of functions through equivalence classes may contribute to a behavior-analytic approach to semantics and generative grammar.     

Controlling relations in conditional discrimination and matching by exclusion.

Normally capable adults learned two-choice identity matching of three-digit numerals and arbitrary matching of physically dissimilar nonsense syllables. The stimuli were displayed on a computer terminal, and responses consisted of typing on the terminal's keyboard. In Experiment 1, every trial displayed a sample numeral, a comparison numeral, and three equal signs (= = =). The comparison stimulus was to be selected if it was identical with the sample; otherwise the equal sign was to be selected. This "single comparison" method was then used to show that arbitrary matching could be based upon either sample-S+ or sample-S- relations. In Experiment 2, a series of probe trials displayed a novel sample, a comparison stimulus from the arbitrary matching baseline, and = = =. Subjects typically selected = = =; they apparently were excluding the baseline comparison stimulus. Experiments 3 through 5 investigated which variables in training would lead to the selection of baseline comparison stimuli in response to novel samples. Behavior was usually unchanged when baseline training included relating comparison stimuli to as many as four different samples. Punishment contingencies were effective, but performance did not generalize unless those contingencies were applied in relation to more than one baseline comparison stimulus.     

Stimulus- and pellet-induced drinking during a successive discrimination

In three experiments, interim water drinking was examined in rats exposed to a multiple schedule whose two components were extinction and a variable-time 30-s schedule of food delivery. Two different drinking patterns were observed in Experiment 1. Pellet-induced drinking, characterized by high rates of postpellet drinking in the variable-time component, with little or no drinking in extinction, occurred when the acquisition of stable postpellet drinking preceded discrimination training. Stimulus-induced drinking, characterized by a burst of drinking at the onset of extinction, with no drinking during the variable-time schedule, occurred when discrimination training preceded all other experimental conditions. With extended training, stimulus-induced drinking eventually was accompanied by postpellet drinking. In Experiment 2, the rate of stimulus-induced drinking and the number of sessions during which it occurred without postpellet drinking were found to be inversely related to component duration. In Experiment 3, the rate of schedule-induced drinking was found to vary directly with component duration.     

Allocation of complex, sequential operants on multiple and concurrent schedules of reinforcement

Pigeons could produce food by pecking exactly four times on each of two keys, in any order. In the first experiment, these response sequences were reinforced on a series of multiple schedules of variable-interval reinforcement. In the second experiment, these response sequences were reinforced on a series of concurrent schedules of reinforcement. In both experiments, highly stereotyped response sequences developed. If these response sequences were treated as individual responses, the resulting data conformed to what is typically reported in studies of multiple and concurrent schedules involving individual responses. For example, behavioral contrast was observed with the multiple schedules, and matching was observed with the concurrent schedules. However, schedule manipulation had no effect on within-sequence characteristics of responses like accuracy, stereotypy, or rate. These data constitute further evidence that response sequences can become functional behavioral units.     

College students' responding to and rating of contingency relations: The role of temporal contiguity

Two experiments investigated the role of temporal contiguity in college students' responding to and rating of contingency relations during operant conditioning. Schedules were devised that determined when but not whether appetitive or aversive events would occur. Subjects' reports concerning the schedules were obtained by means of a 200-point rating scale, anchored by the phrases “prevents the light from occurring” (−100) and “causes the light to occur” (+100). When tapping a telegraph key advanced the time of point gain, responding was maintained or increased and subjects gave positive ratings. When tapping a telegraph key advanced the time of point loss, subjects also gave positive ratings, but responding now decreased. When key tapping delayed the time of point gain, responding decreased and subjects gave negative ratings. When key tapping delayed the time of point loss, subjects also gave negative ratings, but responding now increased. These findings implicate response-outcome contiguity as an important contributor to causal perception and to reinforcement and punishment effects. Other accounts—such as those stressing the local probabilistic relation between response and outcome or the molar correlation between response rate and outcome rate—were seen to be less preferred interpretations of these and other results.     

Rapid determinations of preference in multiple concurrent-chain schedules.

With concurrent chains arranged for a pigeon's key pecks, pecks on two concurrently available initial-link keys (left and right) respectively produce separately operating terminal links (A and B). Preferences for terminal link A over terminal link B are usually calculated as deviations of relative initial-link response rates (left divided by total pecks) from those during baseline conditions, when A equals B. Baseline preferences, however, are often variable and typically are determined indirectly (e.g., with unequal A and B, reversing left-right assignments of A and B over sessions and estimating the baseline from differences between the relative rates generated). Multiple concurrent-chain schedules, with components each consisting of a pair of concurrent chains, speed the determination of preferences by arranging A and B and their reversal within sessions. In two experiments illustrating the feasibility of this procedure, one component operated with circles projected on initial-link keys and the other with pluses; when left and right initial-link pecks respectively produced terminal links A and B in one component, they produced B and A in the other. Even as the baselines fluctuated, preference was observable within sessions as the difference between relative initial-link response rates in the two components. The first experiment demonstrated the rapid development of preferences when terminal links A and B consisted of fixed-interval 15-s and 30-s schedules. The second demonstrated the sensitivity of the procedure to preference for a fixed-interval 30-s schedule operating for pecks on either of two keys (free choice) over its operating for pecks on only a single key (forced choice).     

Rule-governed behavior and sensitivity to changing consequences of responding

Humans were presented with a task that required moving a light through a matrix. Button presses could produce light movements according to a multiple fixed-ratio 18/differential-reinforcement-of-low-rate 6-s schedule, with components alternating every 2 min. Moving the light through the maze earned points worth chances on money prizes. In Experiment 1 four conditions were assessed through between-subject comparisons: minimal instructions, instructions to press rapidly, instructions to press slowly, and instructions that sometimes rapid responding would work while at other times a slow rate would work best. Subjects responded in three successive sessions of 32 min each. The results suggested that instructions affected the nature of the contact made with the programmed consequences and thus subsequent performance. In some cases, responding seemed to result from added contingencies introduced by stating rules. In Experiment 2 the relative contribution of these two effects was assessed by presenting and then withdrawing two lights that had been paired with two specific instructions: “Go Fast” or “Go Slow.” There were three conditions. In one condition, only the Go Fast light was on; in a second, only the Go Slow light was on; and in a third, the lights alternated each minute. In each condition, half the subjects had all instruction lights turned off after the first session. The results once again showed an effect of instructions on contact with the programmed consequences. However, responding sometimes continued in a manner consistent with added contingencies for rule-following even when the programmed consequences had been contacted and would have controlled a different type of responding in the absence of instructions. The relevance of added contingencies for rule-following in determining the effects of explicitly programmed consequences is emphasized.