Punishment of SΔ responding of humans in conditional matching to sample by time-out

Human subjects were intermittently reinforced with money for performing correctly on a conditional matching-to-sample task. The matching performance was examined as a function of a) the duration of Time-Outs (TOs) which followed every incorrect response and b) the frequency (FR value) with which TOs followed incorrect responses. The matching accuracy increased with longer TOs and decreased with less frequent presentation of TOs.     

The effect of multiple SΔ periods on responding on a fixed-interval schedule

The effect of repeated interruption of FI responding by short S^Δ presentations on the pattern of increasing frequency of responding through the interval has been studied. Although the S^Δ profoundly changed the pattern of responding during their presentation, the general scalloped pattern of FI responding survived. The implication of these findings for understanding the role of chaining of responses in FI patterns is discussed. It is suggested that chaining is not a necessary condition for the scalloped pattern.     

Intermittent punishment of human responding maintained by intermittent reinforcement

To determine the effects of variable-interval shock punishment on behavior maintained by variable-interval and variable-ratio reinforcement, human subjects' key-pressing behavior was reinforced with money on a four-component multiple schedule. Components 1 and 2 were variable-interval 30-sec, and Components 3 and 4 were variable-ratio 210. After responding was stabilized, response-contingent electric shock was scheduled on a variable-interval 10-sec schedule during the second and fourth components of each cycle. Subjects instructed as to the reinforcement contingencies showed gradually increasing suppression of variable-interval responding at increasing shock intensities and either very high or very low rates of variable-ratio responding at higher intensities. Minimally instructed subjects showed suppression at higher shock intensities, but no clear differential suppression as a function of reinforcement schedule. Recovery from initial suppression was observed within sessions.     

The effect of multiple SΔ periods on responding on fixed-interval schedule: II. in a primate

A squirrel monkey was subjected to a fixed-interval pattern of reinforcement. During the course of each interval a bright white light was repeatedly presented. In the presence of the white light, a response was never immediately followed by food; the white light thus functioned as S^Δ. Responding was interrupted during the S^Δ periods, but in the squirrel monkey as in the pigeon, these interruptions did not destroy the characteristic scalloped pattern of the cumulatively recorded responding through each interval.     

Chimpanzee responding during matching to sample: control by exclusion

Three chimpanzees performed a computerized matching-to-sample task in which samples were photographs of items and comparison stimuli were geometric symbols called lexigrams. In Experiment 1, samples were either defined (i.e., they represented items that were associated already with a specific lexigram label by the chimpanzees) or undefined (i.e., they did not have an already learned association with a specific lexigram). On each trial, the foil (incorrect) comparison could be either a defined or an undefined lexigram. All 3 chimpanzees selected the correct comparison for undefined samples at a level significantly better than chance only when the foil comparison was defined. In Experiment 2, three comparisons were presented on each trial, and in Experiment 3, four comparisons were presented on each trial. For Experiments 2 and 3, the foil comparisons consisted of either defined or undefined comparisons or a mixture of both. For these two experiments, when the chimpanzees were presented with an undefined sample, they typically made selections of only undefined comparisons. These data indicate that the chimpanzees responded through use of exclusion. A final experiment, however, indicated that, despite the use of exclusion to complete trials with undefined samples correctly, the chimpanzees did not learn new associations between undefined samples and comparisons.     

A sorting‐to‐matching method to teach compound matching to sample

Individuals with developmental disabilities may fail to attend to multiple features in compound stimuli (e.g., arrays of pictures, letters within words) with detrimental effects on learning. Participants were 5 children with autism spectrum disorder who had low to intermediate accuracy scores (35% to 84%) on a computer‐presented compound matching task. Sample stimuli were pairs of icons (e.g., chair–tree), the correct comparison was identical to the sample, and each incorrect comparison had one icon in common with the sample (e.g., chair–sun, airplane–tree). A 5‐step tabletop sorting‐to‐matching training procedure was used to teach compound matching. The first step was sorting 3 single pictures; subsequent steps gradually changed the task to compound matching. If progress stalled, tasks were modified temporarily to prompt observing behavior. After tabletop training, participants were retested on the compound matching task; accuracy improved to at least 95% for all children. This procedure illustrates one way to improve attending to multiple features of compound stimuli.     

The effect of multiple SΔ periods on responding on a fixed-interval schedule: III. Effect of changes in pattern of interruptions, parameters and stimuli

Pigeons responding under fixed-interval schedules of reinforcement were interrupted by S^Δ periods during the course of the intervals. Whether intervals were interrupted by 1, 2, or 5 S^Δ periods, the general scalloped pattern of FI responding persisted. Parameter values up to 27¾ hr for the FI and 2¾ hr for the individual S^Δ interruptions were studied. The results further weaken the hypothesis that the FI pattern of responding depends crucially on control of responding by continuously chained mediating behavior.     

Generalization and discrimination as a function of the SD — SΔ intensity difference

Three groups of four rats were trained on an auditory-intensity discrimination for 21 days. The S^D-S^Δ intensity difference for Group I was 10 db; for Group II, 20 db; and for Group III, 30 db. Following the initial discrimination training, the animals were tested for generalization of the bar-press response to seven novel S^Δ's which were presented intermingled with the original S^D and S^Δ values. Conclusions: (1.) The amount of simple discrimination training required to obtain fairly stable differences in S^D and S^Δ responding is an inverse function of the magnitude of the stimulus difference between S^D and S^Δ. (2.) Generalization gradients obtained immediately following simple discrimination training exhibit a maximum displaced from S^D in a direction also away from S^Δ. (3.) Gradients obtained following continued exposure to the multivalued S^Δ situation show a fairly stable maximum at the S^D value. (4.) Although the gradients tend to fall off systematically on either side of the continuum as distance from S^D is increased, they decrease most rapidly on the S^Δ limb of the gradient.     

Programming stimuli in matching to sample

In these investigations, a “teaching machine” was used to train pre-school and first-grade children in a series of progressively difficult discrimination tasks, leading up to matching to sample. Such training was much more efficient than training in the final discrimination alone. The errors the subjects made were found to be a functon both of the differences between consecutive discriminations (the “size of the steps” in the program) and the length of training on each discrimination. Theoretical and practical implications of these findings are discussed.     

Abortive responding during punishment of bar holding

A continuous chain of homogeneous responding was established in rats by training animals to hold a lever down for 10 sec or longer before releasing it for food reinforcement. When criterion releases were subsequently punished, completed holding chains were greatly suppressed, aborted chains increased markedly, while the rate of chain initiations remained unchanged.     

Some effects of punishment upon unpunished responding

Animals permitted free access to a running wheel and drinking tube increased the amount of running when drinking was punished with electric shock. Additional experiments demonstrated that the simple presence or absence of a drinking tube (or running wheel) was a sufficient condition to observe a decrease or an increase in the alternative response. A quantitative analysis of these interactions observed between the incompatible running and drinking responses suggested that each response occupied a constant proportion of the time available for it. These results question an interpretation of the increase in unpunished alternative responding based upon its avoidance properties.     

Transfer of pigeons' matching to sample to novel sample locations

This study examined the conditions under which conditional stimulus control by the sample stimuli in three-key matching-to-sample paradigms would generalize across the different possible sample locations. In Experiments 1 and 2, the samples appeared on the left and right side keys during initial training and then on the center key during testing. Transfer of pigeons' matching performances to the center-key samples was evident after both identity and symbolic matching training. In Experiment 3, pigeons trained on symbolic matching with two side-key samples or with a side-key and a center-key sample generally transferred their learned matching performances to those samples when they subsequently appeared in the remaining (novel) location. These results indicate that, when two-choice conditional discriminations are learned with more than one sample location, the visual characteristics of the sample per se predominantly come to control the pigeons' comparison choices. This finding encourages the use of the multiple-location training procedure as a way of reducing control by location, thus providing a more discriminating test of symmetry in animals.     

Control by sample location in pigeons'' matching to sample.

Three experiments assessed the impact of sample location in pigeons' matching to sample. Experiments 1 and 2 demonstrated that after line or hue identity matching was acquired to high levels of accuracy with center-key samples, varying sample location across the three keys disrupted performances. The drop in accuracy occurred following both zero-delay and simultaneous training and was mostly confined to trials in which the sample appeared on a side key. Experiment 3 attempted to diminish control by location by training birds to match samples that could appear in any location prior to center-key sample training and moving-sample testing with another set of stimuli. In testing, all birds performed accurately on center-sample trials and on side-key sample trials in which the matching choice appeared on the center key. Accuracy was below chance, however, on side-key sample trials in which the matching choice appeared on the other side key. One implication of the persistent control by sample location in the three-key paradigm is that it precludes the possibility of symmetry because symmetry tests require a change in the locations at which samples and comparisons appear.     

Sample-specific ratio effects in matching to sample

In a symbolic matching-to-sample task, pigeons were trained using sample-specific, fixed-ratio “observing responses.” Subsequently, in a mixed condition, each sample was presented equally often with each ratio requirement, i.e., the ratios were no longer correlated with the samples. In a second experiment, pigeons were trained initially in the mixed condition and subsequently shifted to the sample-specific condition in which the required ratios were correlated with the samples. Results of both experiments suggested joint control of choices by ratio value and by the exteroceptive stimuli. The discriminative properties of the ratios appeared to outweigh absolute ratio-size effects.     

Learning mechanisms in matching to sample.

A model system and an experiment on early learning and decision processes in matching-to-sample and oddity-from-sample tasks are presented. The model system is based, in part, on videotaped records of pigeons' looking responses before they chose 1 of 2 comparison stimuli. In order to see the wavelength stimuli recessed behind the pecking keys, the pigeons had to move in front of them. Although there were slight increases in the acceptance probability with switches between the stimuli before a choice response, the overall decision strategy was close to a Markov choice process in which choice proportions could be predicted by the product of each rejection probability and the final acceptance probability. Learning involved learning to discriminate rather than learning to adopt a stricter criterion for an acceptable sample match.     

The effect of multiple SΔ periods on responding on a fixed-interval schedule: V. Effect of periods of complete darkness and of occasional omissions of food presentations

In pigeons under fixed-interval schedules of reinforcement, responding during most of the interval can be suppressed by stimulus conditions never present when a response is promptly followed by reinforcing stimuli. When the external stimuli obtaining immediately before reinforcement are presented during brief probe periods in the course of the interval, the rate of responding in the probe depends on the temporal position of the probe during the interval; the rate of responding is lower during a probe early in the interval than during one late in the interval. The present experiments show that the temporal dependency still holds (1) in birds with no experience under unmodified fixed-interval schedules, (2) when the time between probes is spent in complete darkness, and (3) when food presentations are omitted at the end of 50% of intervals. The results strengthen and extend the conclusion from previous studies that the time relations themselves are the primary control of rate of responding under fixed-interval schedules of reinforcement.