Context effects on choice.

Four pigeons responded on a concurrent-chains schedule in four experiments that examined whether the effectiveness of a stimulus as a conditioned reinforcer is best described by a global approach, as measured by the average interreinforcement interval, or by a local contextual approach, as measured by the onset of the stimulus preceding the conditioned reinforcer. The interreinforcement interval was manipulated by the inclusion of an intertrial interval, which increased the overall time to reinforcement but did not change the local contingencies on a given trial A global analysis predicted choice for the richer alternative to decrease with the inclusion of an intertrial interval, whereas a local analysis predicted no change in preference. Experiment 1 examined sensitivity to intertrial intervals when each was signaled by the same houselight that operated throughout the session. In Experiment 2, the intertrial interval always was signaled by the stimulus correlated with the richer terminal link. In Experiment 3, the intertrial interval was signaled by the keylights correlated with the initial links and two novel houselights. Experiment 4 provided free food pseudorandomly during the intertrial interval. In all experiments, subjects' preferences were consistent with a local analysis of choice in concurrent chains. These results are discussed in terms of delay-reduction theory, which traditionally has failed to distinguish global and local contexts.     

Stimulus contributions to operant resurgence

In two experiments, pigeons were exposed to a three‐phase resurgence procedure (train Response A; extinguish Response A and train Response B; extinguish Response B). In the first experiment, the stimuli associated with phases were different, resulting in a resurgence procedure combined with an ABC renewal procedure. Presenting the novel stimulus, C, during extinction of both responses in the third phase resulted in minimal resurgence. Subsequently, substituting the original training Stimulus A for Stimulus C resulted in resurgence with all pigeons. In the second experiment, resurgence with the same stimuli present in all three phases of the resurgence procedure (AAA) was compared concurrently with a resurgence procedure in which the ABC renewal procedure used in Experiment 1 was superimposed. Substantially more resurgence occurred with the AAA procedure compared to the ABC procedure. Although ABC renewal in combination with the resurgence procedure generated some resurgence, such recurrent responding was attenuated relative to that observed when the stimulus conditions were constant across phases. Combined with earlier research showing the enhancing effects of combining resurgence and ABA renewal procedures, the present results elaborate on how stimuli correlated with certain behavioral histories affect the course of operant resurgence.     

An immediate-shock freezing deficit with discrete cues: a possible role for unconditioned stimulus processing mechanisms.

Five experiments with C57BL/6 mice (Mus musculus) investigated whether failures in shock processing might contribute to deficits in freezing that occur after an animal receives a shock immediately on exposure to a conditioning context. Experiment 1 found that more contextual freezing resulted from delayed shocks than from immediate shocks across 4 shock intensities. Experiment 2 extended the immediate-shock freezing deficit to discrete stimuli. Experiment 3 found that preexposure to the to-be-conditioned cue did not facilitate immediate cued conditioning. Experiment 4 found that context preexposure enhanced context-evoked fear after an immediate shock. Experiment 5 found that context preexposure also enhanced immediate cued conditioning. These findings are problematic for current theories of the immediate-shock freezing deficit that focus exclusively on processing of the conditioned stimulus, and they suggest that failures in shock processing may contribute to the deficit.     

An experimental analysis of the extinction-induced response burst

The occurrence, time course, and repeatability of response rate increases following the onset of extinction, the extinction burst, were studied in three experiments. Nine pigeons were exposed to at least 5 cycles of 5-session blocks of conditioning followed by 8-session blocks of extinction. In different experiments, conditioning sessions either were a fixed-ratio (FR) or variable-ratio (VR) schedule, and transitions from the last conditioning session in each cycle to the first extinction session were conducted between or within sessions. A single response rate increase occurred when overall response rates were considered. Restricting analyses to the first minute of extinction sessions sometimes revealed increases in response rates, although this finding was inconsistent. The frequency and magnitude of these increases differed across exposures to extinction both across and within pigeons. Additionally, how responding during extinction was measured (i.e., the level of analysis) influenced whether increases above baseline levels were observed. These results suggest that the extinction burst may be influenced by the manner of transition to extinction and the way in which early extinction responding is measured. Under the best conditions, the extinction burst does not appear to be a ubiquitous effect of extinction.     

Radical behaviorism and buddhism: complementarities and conflicts

Comparisons have been made between Buddhism and the philosophy of science in general, but there have been only a few attempts to draw comparisons directly with the philosophy of radical behaviorism. The present review therefore considers heretofore unconsidered points of comparison between Buddhism and radical behaviorism in terms of their respective goals, conceptualization of human beings, and the outcomes of following either philosophy. From these comparisons it is concluded that the commonalities discerned between these two philosophies may enhance both philosophical systems.     

Visual reinforcement in the female Siamese fighting fish, Betta splendens

Operant conditioning with Betta splendens (Bettas) has been investigated extensively using males of the species. Ethological studies of female Bettas have revealed aggressive interactions that qualitatively parallel those between male Bettas. Given these similarities, four experiments were conducted with female Bettas to examine the generality of a widely reported finding with males: mirror-image reinforcement. Swimming through a ring was reinforced by a 10-s mirror presentation. As with males, ring swimming was acquired and maintained when mirror presentations were immediate (Experiments 1, 2, and 3) and delayed (Experiment 4). The failure of conventional extinction (Experiments 1 and 2) and response-independent mirror presentations (Experiment 3) to maintain responding confirmed the reinforcing properties of mirror presentation. These results extend previous findings of mirror images as reinforcers in males of the same species and illustrate a complementarity between behavioral ecology and the experimental analysis of behavior.     

Reinforcement contingencies as discriminative stimuli

A matching paradigm was used to examine the discriminative properties of two different reinforcement contingencies. Responding according to either a differential-reinforcement-of-low-rate or a differential-reinforcement-of-other-behavior schedule produced a choice situation in which each of two keys was illuminated with a unique color. The correct choice response was defined by the contingency that was met to produce the choice. Eighty to 100% correct matching was obtained and recovered during two reversals of the choice stimuli. Introduction of a delay between completion of the reinforcement contingency and presentation of the choice stimuli resulted in decrements in matching performances similar to those obtained when other types of sample stimuli are used. The results provided evidence of the discriminative properties of the relation between behavior and other classes of stimuli.