Negative reinforcement without shock reduction

Stable lever-press responding in rats was reliably produced and maintained by a procedure in which responses could delay shocks without affecting overall shock frequency. Responding was not maintained when the delay-of-shock involved an increase in overall shock frequency.     

Weight reduction as a function of negative covert reinforcement (sensitization) versus positive covert reinforcement

The use of covert or imaginal procedures for weight reduction was evaluated using both positive covert reinforcement and negative (covert sensitization) in group treatment. The results indicate that both of these groups had significantly greater weight losses than a minimal treatment control group. Although the covert, positive reinforcement group did not significantly differ from the negative, its mean weight loss (in lbs) was greater at the end of the four week program. Both groups showed a further weight loss at a three month follow-up, although the changes in mean loss were not statistically significant. The control group, on the other hand, lost a significant amount of weight between the end of treatment and follow-up. However, at follow-up both positive and negative groups still had significantly greater weight losses than the control.     

Secondary reinforcement value of stimuli associated with shock reduction

An experiment is described in which 32 rats were tested to determine if an escape box which had been previously associated with shock reduction had secondary reinforcement value. Subjects were tested in both a fear and a neutral situation. Significant secondary reinforcement effects were found in both situations. However, contary to expectations, greater secondary reinforcement effects were obtained in the neutral than in the fear situation.     

Measuring the difference limen for identification of order of onset for complex auditory stimuli

The approximately 20-msec perceptual threshold for identifying order of onset for components of auditory stimuli has been considered both as a possible factor contributing to the perception of voicing contrasts in speech and as no more than a methodological artifact. In the present research, we investigate the identification of the temporal order of onset of spectral components in terms of the first of a sequence of thresholds for complex stimuli (modeled after consonant-vowel [CV] syllables) that vary in degree of onset. The results provide clear evidence that the difference limen (DL) for discriminating differences in onset time follows predictions based on a fixed perceptual threshold or limit at relatively short onset differences. Furthermore, the DL seems to be a function of context coding of stimulus information, with both the DL and absolute threshold probably reflecting limits on the effective perception and coding of the short-term stimulus spectrum.     

Transfer of the partial reinforcement extinction effect between escape (shock) and appetitive (food) conditioning

In the first experiment rats were given partial reinforcement or continuous reinforcement in either an escape or an appetitive paradigm. Subsequently, the rats received continuous reinforcement training under motivational conditions opposite those experienced earlier. Finally, responses were extinguished according to the motivational conditions experienced in the second phase. The results indicated that partial reinforcement in the initial phase operated to increase resistance to extinction in the last. In a second experiment this intermotivational partial reinforcement extinction effect was shown to survive interpolated experiences with extinction, a 1-week rest period, and continuous reinforcement reacquisition. A third experiment examined the influence of intramodal versus intermodal nonreinforcement-reinforcement sequences on the intermotivational partial reinforcement extinction effect. Interactive effects between similarity of aversive outcome (escape nonreinforcement, appetitive nonreinforcement) and reinforcement type (negative, positive) were found. The theoretical implications of the data from all three experiments are discussed.     

Predator videos and electric shock function as punishers for zebrafish (Danio rerio)

Zebrafish (Danio rerio) are a promising animal model for studying the effects of gene–environment interactions on behavior. Two experiments were conducted to assess punishment effects of presenting predator videos (Indian leaf fish; Nandus nandus) and electric shock on operant approach responses in zebrafish. In Experiment 1, the predator video and shock stimuli were presented upon a response maintained by a single variable‐interval schedule of food reinforcement in different groups of fish. In Experiment 2, the predator video and shock stimuli were presented upon one of two response alternatives maintain by concurrently available variable‐interval schedules of food reinforcement in different groups of fish. Responding decreased when the predator video and shock stimuli were presented relative to their absence in both experiments. Moreover, responding on an unpunished alternative did not reliably decrease in Experiment 2. These results indicate that the decrease in responding resulted from the punishment contingency rather than from elicited species‐specific defense responses or conditioned avoidance. Thus, the predator video and electric shock functioned as punishers of operant behavior for zebrafish. Identifying punishers for this species could lead to research on how gene–environment interactions influence individual differences in sensitivity to punishment.     

Reduction of shock frequency as reinforcement for avoidance behavior

An avoidance technique was used in which rats had two levers available, with independent shock schedules associated with each. Behavioral patterns in initial conditioning and in the maintenance of the responses with various response-shock intervals led to the suggestion that reduction of shock density be considered an important variable in avoidance behavior.     

Induced loudness reduction as a function of frequency difference between test tone and inducer

When a high-intensity tone (inducer) is followed by a moderate-intensity tone (test tone), the loudness of the latter is reduced. This phenomenon, called induced loudness reduction (ILR), depends on the frequency separation of the two tones; as the difference in frequency increases, the amount of ILR decreases. However, the precise course of this decrease is not well known. This article presents two experiments that address this question. In the first experiment, the amount of loudness reduction produced by a 2.5-kHz 80-dB-SPL inducer was measured with the frequency of the test tone swept from 800 Hz to 6 kHz. In the second experiment, the amount of ILR was measured with the same inducer and with test tones set at 2, 2.5, 3, and 4 kHz. Both experiments show that some ILR occurs at frequency separations as wide as four critical bands.     

The intensity-difference limen for 6.5 kHz: an even more severe departure from Weber's law

Intensity-difference limens (DLs) were obtained for tones of 6.5 kHz over levels of 30-90 dB SPL. The tones had Gaussian-shaped envelopes whose duration was expressed as equivalent rectangular duration D, that of a rectangle enclosing the same area as the envelope. D ranged from 0.314 to 30 msec. DL behaviors such as the "severe departure from Weber's law," the "midlevel hump," or the "midduration hump"--that is, a rise in the DL over a range of short durations--were identified using trend analysis. The DL versus level followed a "severe departure" that increased as duration dropped to D approximately 1-2 msec. That midlevel hump then fell with further shortening of the tone pip, producing a mid-duration hump. Materials for this article may be accessed through the Psychonomic Society's Norms, Stimuli, and Data archive, at www.psychonomic.org/archive.     

Choice for signalled over unsignalled shock as a function of shock intensity

Choice between a signalled shock schedule and an unsignalled one was examined at various shock intensities. Three rats were given the opportunity to change from the unsignalled schedule to the signalled one at intensity values between 0.15 mA and 1.0 mA. Steps were usually 0.15 mA and both ascending and descending series were given. For two other rats, shock intensity increased from 0.20 mA to 1.0 mA in 0.20-mA increments; for two additional rats, shock intensity was first 3.0 mA and was then reduced to 1.0 mA. Subjects tended to remain in the unsignalled schedule at the lower shock intensities, but spent most of each session under the signalled schedule at the higher intensities (1.0 mA and 3.0 mA). In addition, the time spent in the signalled schedule tended to vary systematically with shock intensity over at least part of the range of intensity values. It was concluded that the relationship between shock intensity and choice behavior is similar to the relationship between intensity and behavior in procedures involving avoidance, escape, and punishment.     

Partial reinforcement (acquisition) effects within subjects

Acquisition performance of 22 rats in a straight alley runway was examined. The animals were subjected to partial reinforcement when the alley was black (B±) and continuous reinforcement when it was white (W+). The results indicated (a) higher terminal performance, for partial as against continuous reinforcement conditions, for starting-time and running-time measures, and (b) lower terminal performance under partial conditions for a goal-entry-time measure. These results confirm within subjects an effect previously demonstrated, in the runway, only in between-groups tests, where one group is run under partial reinforcement and a separate group is run under continuous reinforcement in the presence of the same external stimuli. Differences between the runway situation, employing a discrete-trial procedure and performance measures at three points in the response chain, and the Skinner box situation, used in its free-operant mode with a single performance measure, are discussed in relation to the present findings.     

The combined effects of noncontingent reinforcement and punishment on the reduction of rumination

The current study extends the literature on the assessment and treatment of rumination through the evaluation of a combined reinforcement‐ and punishment‐based intervention. The study included a single participant with a history of rumination maintained by automatic reinforcement, as identified via a functional analysis. Both noncontingent reinforcement (NCR) with preferred edible items and punishment, in the form of a facial screen, were implemented separately to evaluate their independent effects on the occurrence of rumination. The final treatment package included both NCR and punishment procedures. Implementation of the combined treatment resulted in a 96.5% reduction in rumination relative to baseline. Procedural modifications and integrity errors also were evaluated.