Assessment of attack and drinking in White King pigeons on response-independent food schedules.

Four White King pigeons in Experiment I were exposed to a fixed-time 90-second food schedule with successive access to water and a conspecific target. Drinking per session was sporadic and minimal, while attack per session occurred during most interfood intervals for all animals. Analysis of the temporal distribution of attack showed that the typical postreinforcement pattern of attack developed over the course of the experiment. In Experiment II, the same animals were exposed to a series of fixed-time schedules ranging from 30 to 360 seconds with successive access to water and target. Time engaged in drinking and the number of interfood intervals with drinking were less than that of attack. Food and no-food baselines, which have been typically used to assess schedules-induced drinking and attack, respectively, were used to evaluate the effect of the schedule on attack and water ingestion. Relative to the no-food baseline, both attack and drinking were enhanced by the schedule in all birds. Relative to the food baseline, drinking was slightly suppressed in three birds and attack was enhanced in all. For all animals, the food baseline resulted in more attack and drinking than the no-food baseline.     

Conditional discrimination after errorless and trial-and-error training.

Children were trained on a visual discrimination by stimulus shaping, stimulus fading, or trial-and-error. Those who did not acquire the conditional discrimination received a second, different training. More children initially trained by stimulus shaping acquired the conditional discrimination than did those initially trained with stimulus fading or trial-and-error. After a history of fading or trial-and-error training, children were less likely to acquire the conditional discrimination even after the more successful procedure of shaping was later used.     

Separating the reinforcing and discriminative properties of brief-stimulus presentations in second-order schedules.

Pigeons' responses were maintained under multiple schedules to study properties of briefly presented stimuli. Responses in one component produced food according to a second-order schedule with fixed-interval components in which food or a brief stimulus occurred with equal probability. In the second component responses produced only the brief stimulus under a fixed-ratio schedule. Under various conditions the brief stimulus in the first component was (a) paired with food, (b) not paired with food, (c) partially omitted, or (d) scheduled simultaneously with the second-order schedule under an independent variable-interval schedule. Paired and nonpaired brief stimuli maintained similar response patterning in the second-order schedule. However, only paired stimuli maintained responses in the second component. The data suggest that nonpaired brief stimuli engender response patterning in second-order schedules as a result of their discriminative properties. When the stimulus is paired with food, these discriminative properties sometime mask a reinforcement effect, and no change in response patterning is observed. When the discriminative properties of the brief stimulus are absent, the reinforcing effects of pairing the brief stimulus with food may be observed.     

Comparison of yes-no and latency measures of auditory intensity discrimination.

Rats discriminated auditory intensity differences of sinusoids at 3.0 kilohertz in a go/no-go signal detection procedure. Responses to the signal (hits) were reinforced with electrical brain stimulation, and misses produced a brief timeout. On intermixed noise trials, withholding of responses (correct rejections) was reinforced, and false alarms produced the time-out. In two test conditions, the signal was either the louder (100 decibels) or softer (90, 93, 96, or 99 decibels) of the pair of intensities presented within a set of trials. Each animal was first trained with signal value louder or softer, and reversed for the second condition so that the former noise value served as signal. Hits showed shorter latencies than false alarms, regardless of the relative intensity of signal and noise, and the magnitude of differentiation was proportional to signal-noise separation. Both hits and false alarms showed longer latencies as the discrimination became more difficult. Isosensitivity contours derived from the latencies showed close similarity across conditions; in comparison, the yes-no measure of detectability, d', showed greater variability. The similarity of latency differentiation across louder and softer signal conditions supports a detection model in which the observer's judgment is controlled by the distance of sensory effect from criterion on each trial, as opposed to the loudness of the tones per se.     

Histological data: Hollard and Davison (1971)

As Mogenson and Cioé (1977) have assumed that our electrodes aimed at the ectostriatum (Hollard and Davison, 1971) were actually located there, we feel that a presentation of the histological data is necessary. Following termination of further experiments (Hollard, 1974) the pigeons, numbered 93, 95, and 119, were sacrificed and perfused with saline followed by 10% formalin. Sections, 50 microns thick, were cut on a freezing microtome. Prints were made by mounting each unstained section of a microscope slide and placing them in a standard photographic enlarger. The electrode tips of Pigeons 93 and 119 were located in the paleostriatal complex. The sections of Pigeon 95 were damaged and precise localization was not possible. Further work in this laboratory has also found that, using the same coordinates, electrode tips tend to fall in the paleostriatum, rather than in the more dorsal ectostriatum at which they are aimed. The paleostriatal placements tended to sustain self-stimulation, whereas others located in the ectostriatum sustained relatively low or unstable rates.     

Punishment-specific effects of pentobarbital: dependency on the type of punisher.

Pigeons were trained to peck a key under a multiple random-interval 1-minute, random-interval 6-minute schedule of food presentation. Subsequently, over three phases, additions were made during the random-interval 1-minute component as follows: pecks during the component occasionally were punished by timeout presentation (Phase 1), timeouts were presented independently of responding during the component (Phase 2), pecks during the component occasionally were punished by electric-shock presentation (Phase 3). In Phases 1 and 3, response-dependent timeout and shock suppressed responding and established equivalent rates in both components of the multiple schedule. Intermediate doses of pentobarbital increased responding suppressed by electric-shock punishment but had little or no effect on responding suppressed by timeout punishment. Response-independent presentation of timeouts did not result in suppression of responding (thus showing that response-dependent timeout acted as a punisher), and pentobarbital did not reliably increase unpunished responding. Pentobarbital's selective "punishment-attenuating" properties depend on the nature of the punisher.     

Suppression of ethanol-reinforced lever pressing by delaying food availability.

When food was initially available to rats under a fixed-interval 26-second schedule and each liquid-reinforced lever press delayed food availability 8 seconds, suppression of liquid-reinforced lever pressing and liquid consumption occurred when the liquid presented was 4, 8, 16, 32, and 0% ethanol. Suppression did not occur in yoked-control animals, which received food coincidentally with experimental animals but were not directly exposed to the delay dependency. After exposure to the food schedule, each ethanol solution served as a reinforcer in the absence of food presentation. Delaying food availability for increasingly long periods (8 to 2048 seconds) suppressed ethanol-reinforced lever pressing and consumption relative to baseline levels, with the maximum decrease being below the level maintained in the absence of food. However, degree of suppression did not increase monotonically with delay length. Liquid-reinforced performance of yoked-control animals indicated that suppression did not result from changes in the sequencing of food presentation alone.     

Acquisition of a spatially defined operant with delayed reinforcement.

Two experiments investigated the role of an immediate, response-produced auditory stimulus during acquisition, via delayed reinforcement, of a response selected to control for possible unprogrammed, operandum-related sources of response feedback. Experimentally naive rats were exposed to a delayed-food reinforcement condition, specifically a tandem fixed-ratio 1 differential-reinforcement-of-other-behavior 30-s schedule. The response was defined as breaking a photocell beam located near the ceiling at the rear of the operant conditioning chamber. In Experiment 1, rates of photobeam breaking by each rat increased from near zero, regardless of the presence or absence of a tone that immediately followed the response initiating the delay interval. Though not essential, the tone facilitated response acquisition and resulted in more efficient response patterns at stability. Experiment 2 demonstrated that photobeam-breaking response rates under the delayed reinforcement contingency exceeded those in a preceding baseline condition in which no food was delivered. In addition, upon introduction of the delayed reinforcement procedure, correspondence between response patterns and the requirements of the reinforcement schedule increased over baseline levels in the absence of a food contingency. Together with a previous report of Lattal and Gleeson (1990), the present results suggest that response acquisition with delayed reinforcement is a robust phenomenon that may not depend on a mechanically defined response or an immediate external stimulus change to mediate the temporal gap between response and reinforcer.     

Verbal self-reports about matching to sample: effects of the number of elements in a compound sample stimulus.

Adults' self-reports about their choices in a delayed matching-to-sample task were studied as a function of the number of elements (one, two, or three) in a compound sample stimulus. Signal-detection analyses were used to examine control of self-reports by the number of sample elements, by the speed and accuracy of choices reported about, and by several events contingent on self-reports. On each matching-to-sample trial, a sample element appeared as one of two comparison stimuli. Choice of the matching element, if made within 500 ms of the onset of the comparison stimuli, produced points worth money or chances in a drawing for money, depending on the subject. After each choice, subjects pressed either a "yes" or "no" button to answer a computer-generated query about whether the choice met the point contingency. The number of sample elements in the matching-to-sample task varied across trials, and events contingent on self-reports varied across experimental conditions. In Experiment 1, the conditions were defined by different combinations of feedback messages and point consequences contingent on self-reports, but self-reports were systematically influenced only by the sample-stimulus manipulation. Self-report errors increased with the number of sample elements. False alarms (inaccurate reports of success) were far more common than misses (inaccurate reports of failure), and false alarms were especially likely after choices that were correct but too slow to meet the point contingency. Sensitivity (A') of self-reports decreases as the number of sample elements increased. In addition, self-reports were more sensitive to choice accuracy than to choice speed. All subjects showed a pronounced bias (B'H) for reporting successful responses, although the bias was reduced as the number of sample elements increased and successful choices became less frequent. Experiment 2 demonstrated that the failure of point contingencies to influence self-reports in the first experiment was not due to a general ineffectiveness of the point consequences. Rates of inaccurate self-reports decreased when they resulted in point losses and increased when they resulted in point gains.