We evaluated whether contextual control over equivalence and nonequivalence (i.e., selecting comparisons equivalent to the samples in the presence of a contextual cue, and excluding the selection of comparisons equivalent to the samples in the presence of another contextual cue) can account for apparent arbitrarily applicable relational responding (AARR) in accordance with the frames of sameness and opposition, as defined in relational frame theory (RFT). Three college students were trained to maintain previously established conditional discriminations in the presence of a contextual cue X1, and to reverse them in the presence of another contextual cue X2 (e.g., X1-A1B1, X1-A2B2, X2-A1B2, X2-A2B1). Subsequent tests demonstrated that X1 and X2 functioned as cues for equivalence and nonequivalence. Later on, X1 and X2 were demonstrated to be functionally equivalent to supposed contextual cues for the frames of sameness and opposition employed in RFT studies (i.e., SAME and OPPOSITE cues), in tests for arbitrary and nonarbitrary derived stimulus relations. The functional equivalence of X2 and OPPOSITE suggests that OPPOSITE worked as a cue for nonequivalence. Thus, the results in RFT studies with SAME and OPPOSITE can be explained just by contextual control over equivalence and nonequivalence. Therefore, the explanation that they actually demonstrated AARR in accordance with the frames of sameness and opposition can be questioned and replaced by a more parsimonious explanation, based on a few simple learning principles. We discuss the implications of this conclusion for the debate among competing theories about the origin of stimulus equivalence and other derived stimulus-stimulus relations.

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Contemporary analyses of choice were implemented to analyze the acquisition and maintenance of response allocation in Lewis (LEW) and Fischer 344 (F344) rats. A concurrent-chains procedure varied the delay to the larger reinforcer (0.1, 5, 10, 20, 40, and 80 s). Delays were presented within sessions in ascending, descending, and random orders. Each condition lasted 105 days, and the entire data set was analyzed to obtain discounting functions for each block of 15 sessions and each food delivery across delay components. Both a hyperbolic-decay model and the generalized matching law described well the choices of LEW and F344 rats. Estimates of discounting rate and sensitivity to the immediacy of reinforcement correlated positively. The slope of the discounting function changed with presentation orders of the delays to the larger reinforcer. Extended training reduced differences between the LEW and F344 rats in discounting rates, sensitivity to the immediacy of reinforcement, and estimates of the area under the curve. We concluded that impulsive choice can change as a function of learning and is not a static property of behavior that is mainly determined by genetic and neurochemical mechanisms. Choosing impulsively may be an advantage for organisms searching for food in rapidly changing environments.

We tested whether teaching control by single stimulus samples in conditional discriminations would result in common control of two-stimuli compound samples, and vice versa. In Experiment 1, 5 participants were first taught four single-sample conditional discriminations. The first conditional discrimination was as follows: given sample stimulus P1, select comparison stimulus A1 and not A2; given sample P2 select comparison A2 and not A1. The second conditional discrimination was as follows: given sample P1 select comparison B1 and not B2; given sample P2 select B2 and not B1. Different sample stimuli (Q1 and Q2) were used in the third and fourth conditional discriminations. Moreover, A1 and B1 were presented together as comparisons, such that, if Q1 was presented as the sample, A1 was correct and B1 was incorrect; and if Q2 was presented as the sample, B1 was correct and A1 was incorrect. A2 and B2 were also presented as comparisons. When Q1 was presented, A2 was correct and when Q2 was presented B2 was correct. After training with these four single stimulus sample discriminations, participants were tested with compound PQ samples presented with A1, A2, B1, and B2 as comparisons. If common control were established by the PQ stimuli, a participant would select A1 when P1Q1 was presented, A2 when P2Q1 was presented, B1 when P1Q2 was presented, and B2 when P2Q2 was presented. Such common control by PQ samples occurred in 4 of 5 participants. In Experiment 2, 4 participants were given reverse training. They were first taught to select the A1, A2, B1, and B2 stimuli in response to the appropriate PQ combinations and then probed on the single stimulus sample discriminations. All 4 participants were successful on this probe. Experiments 3 and 4 investigated the effects of teaching additional conditional discriminations with novel stimuli on subsequent transfer from the single-sample discriminations to performance on the compound-sample conditional discrimination.

We evaluated whether contextual control over equivalence and nonequivalence and responding by exclusion can explain the outcomes of relational frame theory (RFT) studies on sameness and opposition relations. We trained nine college students to maintain and reverse conditional discriminations with X1 and X2 as contextual stimuli. In Experiment 1, X1 and X2 controlled derived stimulus relations (DSR) analogous to those controlled by Same and Opposite in RFT studies. These results can be explained by at least two hypotheses: X1 and X2 were cues for equivalence and nonequivalence and responding by exclusion, or for sameness and opposition. In Experiment 2, X1 and X2 controlled DSR predicted by the hypothesis that they were cues for equivalence and nonequivalence and responding by exclusion, and not predicted by the hypothesis that they were cues for sameness and opposition. The results of Experiment 2 and the functional equivalence of X1 and X2 with Same and Opposite in Experiment 1 suggest that Same and Opposite were cues for equivalence and nonequivalence and responding by exclusion in RFT studies.