Autocontingencies: Suppressive and accelerative effects of pairs of shocks superimposed on a positively reinforced operant baseline

Previous research has shown that unsignaled shock may accelerate positively reinforced operant responding if each shock signals a subsequent shock-free period. In order to explore the boundary conditions of this effect, two experiments were performed. In Experiment 1, pairs of unsignaled shocks separated by 15, 30, 60, or 120 seconds resulted in suppressed responding during the briefest intershock interval, and in accelerated responding during the longer intervals. When the second shock in each pair signaled a shock-free period of at least 3 minutes, accelerated responding also followed offset of the second shock in all but the 30-second condition. In Experiment 2, the addition of a conditioned stimulus prior to each pair of shocks restored baseline responding, and eliminated accelerative control following the second shock only under the briefest inter-shock interval. The results are discussed in terms of the similarity between autocontingencies (shock/no-shock relations; Davis, Memmott, & Hurwitz, 1975) and recent modifications of the feature-positive procedure (e.g., Reberg & Memmott, 1979), which stress stimulus control by shock/no-shock relationships.     

Effects of morphine, clonidine, and intensity change on electric-shock discrimination.

The effects of morphine, clonidine, and changes in stimulus intensity were examined in squirrel monkeys responding on one of two levers following brief presentations of one of two electric-shock intensities (0.1 and 0.5 mA). Responses were designated as correct or incorrect depending on which shock intensity had been presented and which lever was pressed. Morphine (0.42 to 1.80 mg/kg) and clonidine (0.075 to 0.18 mg/kg) decreased percentage correct responding. Morphine and clonidine also increased response latency and the number of shock presentations that were not followed by responses. Changes in shock intensity also decreased percentage correct responding but had no effect on response latency or on the number of shock presentations not followed by responses.     

Revising recognition judgments during noisy recognition evidence accumulation: The dynamics of losses versus gains

Outside the laboratory, we sometimes revise our recognition judgments of others—realizing, for example, that we have accidentally failed to greet an acquaintance we just passed in the hallway. These recognition reversals have rarely been studied. Here, using a basic noisy-accumulation framework, we simulated recognition response reversals in which initial speeded recognition judgments were followed by an opportunity to revise the initial judgment. The simulation predictions were compared to empirical data from two experiments in which we gave participants the opportunity to revise each of their initial speeded recognition judgments. The speeded old–new responses were restricted to either 300–800 ms (Exp. 1) or 200–600 ms (Exp. 2) after each probe’s onset, and the second response was self-paced in both experiments. The noisy-accumulation framework correctly anticipated three findings. First, gain rates (incorrect followed by correct responses) always exceeded loss rates (correct followed by incorrect responses). Second, despite being corrective, the raw gain rates exhibited a modest negative correlation with overall recognition skill. Third, when gain rates were conditioned on the opportunity to correct an initial error (conditional gain rate), they were then positively correlated with recognition skill but were less diagnostic than the conditional loss rates. Thus, the mechanics of noisy accumulation naturally predict that skilled recognizers will demonstrate infrequent corrective behavior but a high probability of correction, should an initial error occur.     

The effects of a pre-time-out stimulus on matching-to-sample of humans,

In each of two experiments human subjects were intermittently reinforced with money on a fixed-ratio schedule for emitting correct matching responses. A pre-time-out stimulus which signaled removal of positive reinforcement was periodically superimposed. In the first experiment the superimposed pre-time-out stimulus was paired with a 1-min or 4-min response-independent time out. In the second experiment the pre-time-out stimulus was paired with a 1-min or 4-min time out contingent on the incorrect responses. The pre-time-out stimulus did not markedly influence performance when the time out was response independent. In contrast, the pre-time-out stimulus markedly suppressed incorrect responding when the time out was contingent on the incorrect responses. When duration of this time-out was increased from 1-min to 4-min, suppression of incorrect responding increased and correct responding was suppressed. Therefore, behavioral suppression by a pre-time-out stimulus was obtained only when the signaled aversive event-time out-was response produced. In this case, suppression was influenced by time-out duration.     

Learned helplessness in the rat.

Four experiments attempted to produce behavior in the rat parallel to the behavior characteristic of learned helplessness in the dog. When rats received escapable, inescapable, or no shock and were later tested in jump-up escape, both inescapable and no-shock controls failed to escape. When bar pressing, rather than jumping up, was used as the tested escape response, fixed ratio (FR) 3 was interfered with by inescapable shock, but not lesser ratios. With FR-3, the no-shock control escaped well. Interference with escape was shown to be a function of the inescapability of shock and not shock per se: Rats that were "put through" and learned a prior jump-up escape did not become passive, but their yoked, inescapable partners did. Rats, as well as dogs, fail to escape shock as a function of prior inescapability, exhibiting learned helplessness.     

The emergence of symmetry in a conditional discrimination task using different responses as propioceptive samples in pigeons

In Experiment 1, 10 pigeons were exposed to a successive symbolic matching-to-sample procedure in which the sample was generated by the pigeons' own behavior. Each trial began with both response keys illuminated white, one being the "correct" key and the other the "incorrect" key. The pigeons had no way of discriminating which key was correct and which incorrect, since these roles were assigned on a random basis with the same probability of 0.5 for each key. A fixed ratio of five responses was required on the correct key. However, each time the pigeon pecked the incorrect key, the correct key response counter reset. Five consecutive pecks on the correct key was the only way to end this component, and switch off both key lights. Two seconds later, these same keys were illuminated again, one green and the other red (comparison stimuli). Now, if the correct white key had been on the left, a peck at one color produced food, and if the correct white key had been on the right, a peck at the other color produced food. When the pigeons had learned this discrimination, they were exposed to several symmetry tests (simultaneous presentations of both keys illuminated the same color-i.e., both red or both green), in order to interchange the sample with the comparison stimuli. In Experiment 2, the importance of requiring discrimination between the samples and between the comparisons was analyzed. In Experiment 3, we compared the results of Experiment 1 with a slightly different experiment, which resulted in discrimination of key position, an exteroceptive stimulus. The results showed that symmetry emerged only when different responses were used as samples.     

Fractional punishment of fixed-ratio performance

Key-peck responses of pigeons under a fixed-rate 60 (Exp. I) or fixed-ratio 99 (Exp. II) schedule of positive reinforcement were punished by response-dependent electric shock during a segment of the ratio. The punishing stimulus was scheduled in one of three locations: the first third of the ratio, the middle third, or the final third. At high shock levels, the different loci of punishment differentially affected the typical fixed-ratio performance pattern. Post-reinforcement pauses were lengthened by all punishment conditions but to a greater degree when the responses in initial third of the ratio were punished. Disruption of responses before the punished segment of the ratio was a conspicuous feature of the performances when the middle or final third of the ratio was punished. Two of the punishment conditions produced similar effects on both fixed-ratio baselines but punishing the final third of the ratio suppressed the punished responses of the ratio only with the fixed-ratio 99 schedule. General effects of all punishment conditions included consistent intra-session recoveries of partially suppressed performances, the rapid recovery of the FR performances after the punishment dependency was removed after complete suppression, and the facilitation of overall and/or local response rates of most subjects by low-intensity shock.     

Discrimination learning by macaca mulatta with option to switch between S+ and S−

Three rhesus monkeys were trained to press either of two response keys. A response on the reinforcement key during presentation of the reinforced stimulus produced a sucrose pellet followed by an intertrial interval, but during presentation of the unreinforced stimulus produced only the intertrial interval. A response on the switching key changed the discriminative stimulus from reinforced to unreinforced or from unreinforced to reinforced. The reinforced stimulus was presented automatically on half the trials, but could be produced only by a switching response on the other half. Switching tended to occur in three distinct stages during acquisition of discriminative behavior. The first stage was identified as "nondiscriminative switching"; the second as "nonswitching"; and the third as "discriminative switching".     

The distribution of observing responses in a mixed FI-FR schedule,

In Exp I, three pigeons were trained on an observing response procedure where observing responses produced a stimulus correlated either with FI or with FR. Stimulus duration was 30 sec. During FR, the subjects completed the ratio before the stimulus terminated. During FI, the subjects usually observed the stimulus only once. Observing responses occurred immediately after food reinforcement. In Exp II, stimulus duration was shortened to 5 sec and the FR for food was increased. The results were similar to those of Exp 1. During most FIs and FRs, only one observing response occurred. The results of both experiments could be interpreted in a response competition framework. Immediately after food reinforcement, observing behavior is strong. When behavior on the food key begins it competes with further observing behavior.     

Where did you go wrong? Errors, partial errors, and the nature of human information processing

Human performance is seldom perfect, and even when an overt response is correct it may be accompanied by partial-error activity that does not achieve the level of a complete incorrect response. Partial errors can be detected in measures of the lateralized readiness potential, of the electromyogram, and of response force. Correct responses accompanied by partial errors tend to have slower reaction times than “clean” correct responses (because of response competition), and condition differences in reaction time can, on some occasions, be explained in terms of differences in the incidence of partial errors. In two-choice reaction time tasks, partial errors are more frequent when the imperative stimulus contains information that favors both responses, than when it contains information that favors only one response. The non-random nature of partial errors supports the inference that partial information about the stimulus is used to guide responses. A similar inference is supported by the observation that, in hybrid choice Go/No-go tasks, the kinds of partial errors that follow a No-go stimulus represent activation of the response that would have been correct had the stimulus been a Go stimulus. Finally, we note that the human processing system is capable of monitoring its own behavior and of initiating remedial actions if necessary. The activity of an error-detection system, as revealed by measures of the error-related negativity, is related to the degree to which responses are slowed after errors.     

On the role of covarying functions in stimulus class formation and transfer of function

This experiment investigated whether directly trained covarying functions are necessary for stimulus class formation and transfer of function in humans. Initial class training was designed to establish two respondent-based stimulus classes by pairing two visual stimuli with shock and two other visual stimuli with no shock. Next, two operant discrimination functions were trained to one stimulus of each putative class. The no-shock group received the same training and testing in all phases, except no stimuli were ever paired with shock. The data indicated that skin conductance response conditioning did not occur for the shock groups or for the no-shock group. Tests showed transfer of the established discriminative functions, however, only for the shock groups, indicating the formation of two stimulus classes only for those participants who received respondent class training. The results suggest that transfer of function does not depend on first covarying the stimulus class functions.     

The effects of number of sample stimuli and number of choices in a detection task on measures of discriminability

Six pigeons were trained on a conditional discrimination task involving the discrimination of various intensities of yellow light. The research asked whether stimulus—response discriminability measures between any pair of stimuli would remain constant when a third or fourth sample and reinforced response were added. The numbers of different sample stimuli presented and different responses reinforced were two (Part 1), three (Parts 2 and 4), and four (Part 3). Across conditions within parts, the ratios of reinforcers obtainable for correct responses were varied over at least five levels. In Part 5, the numbers of sample stimuli and reinforced responses were varied among two, three, and four, and the reinforcer ratio between consecutive remaining samples was constant at 2:1. It was found that once a particular response had been reinforced, subjects continued to emit that response when the conditional stimulus for that response was no longer presented. Data analysis using a generalization-based detection model indicated that this model was able to describe the data effectively. Four findings were in accord with the theory. First, estimates of stimulus—response discriminability usually decreased as the arranged physical disparity between the sample stimuli decreased. Second, stimulus—response discriminability measures were independent of response—reinforcer discriminability measures, preserving parameter invariance between these measures. Third, stimulus—response discriminability measures for constant pairs of conditional stimuli did not change systematically as conditional stimulus—response alternatives were added. Fourth, log stimulus—response discriminability values between physically adjacent conditional stimuli summed to values that were not significantly different from estimates of the discriminability values for conditional stimuli that were spaced further apart.     

The effects of electroconvulsive shock on the action of a reinforcing stimulus

Three experiments sought to evaluate the effect of electroconvulsive shock on the action of a reinforcing stimulus. In all experiments behavior was maintained on a 2 min variable interval schedule for food reinforcement. Foot shock at the termination of a buzzer stimulus served as the reinforcing stimulus for conditioned suppression during the ensuing buzzer interval. Omission of foot shock at the termination of the buzzer stimulus was followed by normal responding (no conditioned suppression) during the next buzzer interval. In Exp I electroconvulsive shock followed foot shock at varying time intervals. In the first subsidiary experiment electroconvulsive shock followed an unreinforced buzzer stimulus at varying time intervals. In the second subsidiary experiment electroconvulsive shock followed foot shock at varying time intervals and an additional buzzer stimulus was sounded between the termination of foot shock and the onset of electroconvulsive shock. These three experiments demonstrated that electroconvulsive shock invariably abolished the effects of the reinforcing stimulus if it followed conditioning by no more than 10.0 sec and never had an effect if it followed conditioning by 12.5 sec or more; electroconvulsive shock was not acting as a reinforcing stimulus in this situation.     

Discrete-trial training for autistic children when reward is delayed: a comparison of conditioned cue value and response marking

Three children with autism were taught to identify pictures of objects. Their speed of acquisition of receptive speech skills was compared across two conditions. In the cue-value condition, a compound audiovisual stimulus was presented after correct responses and again when a primary reinforcer was delivered after a 5-s delay; in the response-marking condition, a second stimulus was presented after both correct and incorrect responses, but not prior to the primary reinforcer. In both conditions primary reinforcement was delayed for 5 s. Although the children learned receptive speech skills in both conditions, acquisition was faster in the cue-value condition.     

Immediate reinforcement in delayed reward learning in pigeons

Pigeons were trained on simultaneous red-green discrimination procedures with delayed reward and sequences of stimuli during the delay. In Experiment 1, three stimuli appeared during the 60-second intervals between the correct responses and reward, and the incorrect responses and nonreward. The stimulus that immediately followed a correct response also preceded nonreward, and the stimulus that followed an incorrect response preceded reward. These stimuli were 10 or .33 second in duration for different groups. Stimuli during the remainder of the delay interval differed following correct and incorrect responses. Group 10 initially persisted in the nonrewarded choice, but shifted to a preponderance of rewarded responses after further training. Group .33 rapidly acquired the correct response. Similar results were obtained in Experiment 2 where delay intervals consisted of opposite sequences of two stimuli of equal duration and total delays were 6, 20, or 60 seconds. Early in training, generalization of differential conditioned-reinforcing properties from the conditions preceding reward and nonreward to postchoice conditions had a greater effect relative to backchaining than it did later. It was concluded that delayed-reward learning is best analyzed in terms of the conditioned-reinforcing value of the patterns of cues that follow immediately after rewarded and nonrewarded responses.     

Cardiac and respiratory conditioning, differentiation, and extinction in the pigeon

Paired light and foot shock in 12 pigeons rapidly developed acceleratory heart and respiratory conditioned responses. Sensitization and stimulus control birds did not condition. When a different colored stimulus light that was not reinforced was mixed in a random series with the reinforced light, rapid differentiation of both heart and respiratory responses occurred. In most cases neither heart nor respiratory conditioned responses could be extinguished by 100 non-reinforced presentations of the conditioned stimulus.     

Stimulus Presentation Ratios And The Outcomes For Correct Responses In Signal-detection Procedures

Three pigeons were trained to discriminate between two line orientations (S₁ and S₂). A left-key peck was correct when S₁ was presented, and a right key-peck was correct when S₂ was presented. In all procedures, correct responses were occasionally reinforced with food paired with the presentation of the magazine light. Incorrect responses produced a blackout. Six detection procedures were used. In the first, the signal presentation ratio was varied across conditions and the reinforcer ratio was allowed to covary. In the second, the signal presentation ratio was held constant at 1:1 and the reinforcer ratio varied across conditions. In the third, the signal presentation ratio was varied across conditions and the reinforcer ratio was held constant at 1:1. In these three procedures, correct responses that were not scheduled for reinforcement were followed by blackout. The remaining three procedures repeated those described above with one procedural change: Nonreinforced but correct trials were followed by the presentation of the magazine light. Birds showed systematic preferences for the key associated with the stimulus presented or reinforced most often. There was no change in the birds' performance over changes in the feedback for nonreinforced but correct responses.     

Bias functions and operating characteristics of rats discriminating auditory stimuli

Rats were trained to discriminate between two bursts of random noise that differed in intensity. In a two-lever, discrete-trial procedure, correct responses were reinforced with brain stimulation, and incorrect responses produced timeout. Responding was studied as a function of the decibel difference between the stimuli, the probabilities of presenting the stimuli, the relative duration of timeout consequent upon the two types of incorrect responses, and the absolute duration of timeout consequent upon incorrect responses. The results showed that the distribution of responses between the two levers depended upon the stimulus probabilities, but were independent of either the absolute or relative durations of timeout. When the stimulus probabilities were varied, the response probabilities did not match the stimulus probabilities; when the relative durations of timeout were varied, the animals did not obtain the maximum rate of reinforcement per unit time. Instead, the animals distributed their responses so as to obtain the maximum number of reinforcements at each level of discrimination. In addition, the level of discrimination increased as a function of the decibel difference between the stimuli.     

Signal probability, reinforcement and signal detection.

Five pigeons were trained to detect differences in light intensity. Two stimuli, S1 and S2, differing in intensity, were arranged on the center key of a three-key chamber according to set probabilities. A peck on the center key turned on the two side keys. When S1 was presented on the center key, a peck on the left key was "correct" and when S2 was presented, a peck on the right key was "correct." Correct responses produced reinforcement and incorrect responses produced 3-second blackout. Detection performance was measured under three procedures. The first was a standard signal-detection design in which the probability of S1 was varied and the number of reinforcements obtained for correct responses to S1 was allowed to covary. In the second procedure, the probability of S1 was again varied but the distribution of reinforcements between the two choices was kept equal. In the third procedure, probability of S1 was held constant while the distribution of reinforcements was varied between the two choices. Changes in response bias were a function of variations in the relative reinforcement ratio for the choice responses and not a function of variations in the probability of stimulus presentation. Discriminability remained constant across the three procedures.     

Concurrent performances: effect of punishment contingent on the switching response

Pigeons' key-pecking responses were maintained under concurrently available variable-interval schedules of reinforcement. Responses in the presence of two different key-colors were reinforced on two independent and concurrent variable-interval schedules of food reinforcement, each associated with one of the key colors (red or green). Pecks at a second key (changeover key), always white, would alternate the colors on the main key. In Exp. 1 and 2, electric shock of 50 msec duration followed immediately after changeovers. The proportion of responses in the presence of the color associated with the higher frequency of reinforcements per hour was a direct function of shock intensity contingent on changeovers. When both schedules provided equal number of reinforcements per hour, there was no systematic effect of shock intensity on response distribution. In Exp. 3, a timeout period was contingent on changeovers, and response distribution was a function of timeout length.