The effect of redundant contextual stimuli on autoshaping the pigeon’s keypeck

Motivational competition and the paraventricular thalamus

Although significant progress has been made in understanding the behavioral and brain mechanisms for motivational systems, much less is known about competition between motivational states or motivational conflict (e.g., approach - avoidance conflict). Despite being produced under diverse conditions, behavior during motivational competition has two signatures: bistability and metastability. These signatures reveal the operation of positive feedback mechanisms in behavioral selection. Different neuronal architectures can instantiate this selection to achieve bistability and metastability in behavior, but each relies on circuit-level inhibition to achieve rapid and stable selection between competing tendencies. Paraventricular thalamus (PVT) is identified as critical to this circuit level inhibition, resolving motivational competition via its extensive projections to local inhibitory networks in the ventral striatum and extended amygdala, enabling adaptive responding under motivational conflict.

Translations in Stimulus-Stimulus Pairing: Autoshaping of Learner Vocalizations

Stimulus-stimulus pairing (SSP) is a procedure used by behavior analysis practitioners that capitalizes on respondent conditioning processes to elicit vocalizations. These procedures usually are implemented only after other, more customary methods (e.g., standard echoic training via modeling) have been exhausted. Unfortunately, SSP itself has mixed research support, probably because certain as-yet-unidentified procedural variations are more effective than others. Even when SSP produces (or increases) vocalizations, its effects can be short-lived. Although specific features of SSP differ across published accounts, fundamental characteristics include presentation of a vocal stimulus proximal with presentation of a preferred item. In the present article, we draw parallels between SSP procedures and autoshaping, review factors shown to affect autoshaping, and interpret autoshaping research for suggested SSP tests and applications. We then call for extended use and reporting of SSP in behavior-analytic treatments. Finally, three bridges created by this article are identified: basic-applied, respondent-operant, and behavior analysis with other sciences.

An Examination of Autoshaped Keypecking in a Dark Chamber

Three experiments investigated critical variables influencing the development of autoshaping in a dark chamber. The context in which magazine-training occurred, length of intertrial interval, and CS intensity were the independent variables. Performance was best following magazine-training in the light; 60-sec. intertrial interval was better than 25; and little responding developed with a bright CS. These results are discussed with reference to the cue-localization hypothesis and a context-blocking effect.

Interactions in multiple schedules: the role of the stimulus-reinforcer contingency

In Experiments I and II, pigeons were exposed to single-key multiple schedules of response-independent and -dependent food presentation. Components were correlated with different keylights. When the rate of food presentation in the first component exceeded that in the second component, the local rate of key pecking was relatively high at onset of the first component. Overall rate in that component varied inversely with component duration and the rate of food presentation in the second component. When responding was maintained in the second component, the local rate of key pecking was relatively low at onset of that component. Overall rate in the second component varied directly with component duration and the rate of food presentation in that component. In Experiment III, pigeons were exposed to a two-key multiple schedule. Pecks on a constantly illuminated key produced food. Components were correlated with the color of a second key on which pecks had no scheduled consequences. The effects of component duration and rate of food presentation under the single-key response-dependent schedule were synthesized by combining response rates on each concurrently available key under the two-key procedure. The results support an account of multiple-schedule interactions in terms of the joint influence on responding of stimulus-reinforcer and response-reinforcer contingencies.

Stimulus generalization from feeder to response key in the acquisition of autoshaped pecking

During autoshaping, a 6-second presentation of one stimulus and a variable time 30-second presentation of a second stimulus alternated in appearance on a pigeon key. Grain always was delivered for 3 seconds at the end of the first stimulus interval. In the first experiment, autoshaped pecking of the stimulus preceding grain delivery began much sooner when that stimulus was a black vertical line on a white background and the other stimulus was green than when the opposite stimulus arrangement was used. Because these two stimuli differed in form, hue, brightness, and similarity in hue and brightness to the illumination of the raised feeder, three subsequent experiments examined whether the differential speed of autoshaping in the two groups was due to a feature-positive, feature-negative effect, a preference for brighter over darker stimuli, a simple preference for white over green, or stimulus generalization from the brightness or hue of the illuminated, raised feeder to the stimulus on the key preceding grain delivery. The data from these experiments showed that the first autoshaped key peck was most likely to be made to the stimulus of the same hue as that illuminating the feeder, regardless of whether that stimulus was positively or negatively associated with grain delivery. At least under some conditions, therefore, stimulus-generalization mediated response transfer of pecking grain in the presence of the hue illuminating the feeder to pecking the key illuminated by a similar hue appears to account for the occurrence of autoshaped key pecking.

Effect of varying the duration of grain presentation on automaintenance

In a series of three experiments the effects of variation in grain duration on automaintenance were evaluated. In the first experiment, key illumination was followed by grain only when pigeons did not peck the key. Each subject was exposed to 2-, 4-, and 8-second feeder durations in blocks of 10 sessions. Subjects pecked on a high percentage of trials at all feeder durations. The mean peck latency was shorter in the 8-second condition than in the two other conditions in five of six subjects. The conditional probability of pecking given successive keylight-grain pairings did not increase as the number of pairings increased. The second experiment was identical to the first, except that key pecking had no scheduled consequence. Under these conditions, all three subjects showed substantial responding. The recorded measures showed no systematic relationship to feeder duration in this study. In the third experiment, two different stimuli were followed by feeder presentations of either identical (2- or 8-second) or different (2- and 8-second) durations within each session. Subjects tended to respond sooner and with a higher overall rate in the presence of the stimulus associated with the longer feeder duration only when different feeder durations were presented within the same session. This result was confirmed by direct observation of the pigeons. The results of these experiments suggest that the effects of varying grain duration may be small, compared to the effects of varying other variables. The results also suggest that the location as well as the frequency of pecking may be an important measure in the analysis of factors controlling the pigeon's key peck.

A comparison of pecking generated by serial, delay, and trace autoshaping procedures

Pigeons were exposed to serial, delay, and trace autoshaping procedures. In Experiment I, all conditioned stimuli (CSs) were changes in illumination of the response key. The number of trials to acquisition of the keypeck increased from serial, to 4-sec delay, 8-sec delay, and 8-sec trace procedures, in that order. In Experiment II, which used a longer intertrial interval, trials to criterion increased from 8-sec delay, to 28-sec delay, 8-sec trace, and 28-sec trace procedures, in that order. In Experiment III, two groups received serial procedures in which the first CS was either a tone or a houselight, and the second was a keylight. The tone group acquired the key peck more rapidly than the houselight group. Early in conditioning in these experiments, and when the conditioned stimulus was a change in the keylight, there was a short latency to the onset of pecking and pecking was directed at the CS. After extensive conditioning, or when the CS was relatively diffuse, pecking still occurred, but had a longer latency and was not reliably directed toward the conditioned stimulus.

Trace autoshaping: Acquisition, maintenance, and path dependence at long trace intervals

The pigeon's tendency to acquire and maintain signal-directed key pecking under a trace conditioning procedure was parametrically examined. In Experiment 1, the percentage of CS trials with a key peck response was a decreasing function of the trace interval for separate groups of pigeons. The majority of subjects acquired signal-directed key pecking with trace intervals as long as 36 sec. In Experiment 2, differential maintenance of key pecking occurred across trace intervals in a within-subject procedure. Maintenance of key pecking at 36- and 60-sec trace intervals was path dependent in that responding depended on the subject's performance under the preceding trace interval.

Rate and temporal pattern of key pecking under autoshaping and omission schedules of reinforcement

The role of response-reinforcer contiguity on autoshaped key pecking in pigeons was studied by scheduling response-dependent nonreinforcement at the beginning or the end of brief (8-sec) discrete trials. Schedules that permitted chance conjunctions of key pecking and food sustained high rates of responding, whereas those that prevented the occurrence of key peck-food intervals shorter than 4 sec sustained low response rates. In addition, selective reinforcement schedules supported accelerating or decelerating rates of responding within individual trials. These effects were traceable to response-reinforcer (operant), but not stimulus-reinforcer (respondent) factors.

Automaintenance without stimulus-change reinforcement: Temporal control of key pecks

Yoked pairs of experimentally naive pigeons were exposed to a modified autoshaping procedure in which key pecking by the leader birds postponed both keylight termination and access to grain for the leader and the follower bird. Key pecking developed and was maintained in all birds and continued through two reversals of roles in the yoked procedure. Although temporal control developed more slowly in follower birds, asymptotic temporal distributions of key pecking were similar for all birds in both leader and follower roles; maximum responding occurred soon after keylight onset and decreased to a minimum prior to reinforcement. Response distributions for both leader and follower birds were described by Killeen's (1975) mathematical model of temporal control. Follower birds received response-independent reinforcement, and the development by these birds of temporal distributions which are minimal immediately prior to reinforcement is without precedent in Pavlovian appetitive conditioning. However, maintenance of key pecking by the leader birds, whose responses postponed both stimulus-change and food reinforcement, supports an interpretation of autoshaped and automaintained key pecking as responding elicited by signaled grain presentation.

Key-peck durations under behavioral contrast and differential reinforcement

Pigeons were maintained on a multiple schedule in which both components were variable-interval one-minute schedules. When they were switched to a condition in which one component was extinction, behavioral contrast was observed. The median durations of the key pecks in the unchanged component did not decrease in size. The results are incompatible with a theory of behavioral contrast which considers the added pecks to be short-duration responses. In a second experiment, pigeons were required to emit short-duration key pecks in one component of a multiple schedule, and long-duration pecks in the other. Two of three pigeons learned to emit responses appropriate to the requirements of the component in effect, suggesting that the duration of the key-peck response is sensitive to differential reinforcement.

Stimulus-reinforcer contingencies and local behavioral contrast

Four pigeons were exposed to a series of multiple schedules of variable-interval reinforcement in which pecks were required on one key (operant key) and components were signalled on a second key (signal key). Four additional pigeons experienced identical conditions, except that a yoking procedure delivered food on variable-time schedules, with no key pecks required. One of the components of the multiple schedule was constant throughout the experiment as a variable-interval (or variable-time) 30-second schedule. Operant-key responding during the constant component was uniform throughout the component, uninfluenced by changes in the duration of the variable component, and only slightly influenced by changes in reinforcement frequency correlated with the variable component. By comparison, signal-key response rate during the constant component was highest at the onset of the component, was higher when the variable component was 60-sec long than when it was 1-sec long, and was higher when no reinforcement occurred in the variable component than when reinforcement was scheduled in the variable component. These characteristics of signal-key pecking matched characteristics of local positive behavioral contrast. These data are taken to support the "additivity theory" of behavioral contrast and to suggest that Pavlovian stimulus-reinforcer relations contribute primarily to the phenomenon of local positive contrast.

The disruption of autoshaped key pecking in the pigeon by food-tray illumination

Two experiments investigated the effect of food-tray illumination on pecking a lighted key that signalled food presentation. Pigeons key pecked less when both feeder and key stimuli preceded grain delivery than when the keylight alone signalled food. This detractive influence of grain-tray illumination did not result after prior pairings of the keylight with food. The involvement of associative and physical variables in autoshaping the pigeon's key peck is considered in light of these findings.

Key pecking in pigeons produced by pairing keylight with inaccessible grain

In Experiment I, keylight was paired with inaccessible grain delivery (under two conditions of keylight intensity) to determine if autoshaping would occur in the absence of primary reinforcement. In Experiment II, the procedure was repeated with accessible grain, for comparison. In Experiment III, the procedures were repeated with explicitly unpaired presentations of keylight and either inaccessible or accessible grain. The results indicated that key pecking occurred as quickly in the presence of keylight pairings with inaccessible grain as with accessible grain, though (except for one bird) key pecking was not maintained with inaccessible grain. Furthermore, compared to the dim keylight, the bright keylight greatly suppressed key pecking when paired with inaccessible grain, and reduced the rate of key pecking when paired with accessible grain. Little key pecking occurred in groups exposed to explicitly unpaired presentations of keylight (whether bright or dim) and grain (whether accessible or inaccessible). When the birds in Experiment III were retested with explicitly paired presentations of keylight and grain, little key pecking was observed, suggesting suppressive effects of prior explicitly unpaired presentations. It is suggested that the effects of key-brightness manipulation were produced by the association of grain with cues other than the response key, or by distraction produced by partial illumination of the grain hopper.

Differential autoshaping to common and distinctive elements of positive and negative discriminative stimuli

The learning by hungry pigeons of a discrimination between two successively presented compound visual stimuli was investigated using a two-key autoshaping procedure. Common and distinctive stimulus elements were simultaneously presented on separate keys and either followed by food delivery, S+, or not, S-. The subjects acquired both between-trial and within-trial discriminations. On S+ trials, pigeons pecked the distinctive stimulus more than the common stimulus; before responding ceased on S- trials, they pecked the common stimulus more than the distinctive one. Mastery of the within-display discrimination during S+ trials preceded mastery of the between-trials discrimination. These findings extend the Jenkins-Sainsbury analysis of discriminations based upon a single distinguishing feature to discriminations in which common and distinctive elements are associated with both the positive and negative discriminative stimuli. The similarity of these findings to other effects found in autoshaping-approach to signals that forecast reinforcement and withdrawal from signals that forecast nonreinforcement-is also discussed.

Some variables affecting rate of key pecking during response-independent procedures (autoshaping)

Rate of key pecking by pigeons subjected to response-independent procedures in which a stimulus on the response key preceded food presentation was investigated in eight experiments. Color and shape of the stimulus, duration of the stimulus, probability of food following the stimulus, duration of the intertrial interval, and duration of food presentation were varied separately and in combination. All variables studied, except color and shape of the stimulus, had a reliable effect on pecking rate, but some variables had stronger effects than others. Rapid key pecking may be obtained with a variety of response-independent procedures, as well as by response-dependent reinforcement. The results of experiments in which food is both dependent on key pecking and correlated with stimulus conditions are not representative of simple operant effects. Key pecking is an ideal response for studying the simultaneous operation of response-reinforcer and stimulus-reinforcer effects.

Stimulus control of schedule-induced activity in pigeons during multiple schedules

Stimulus control of schedule-induced general activity was demonstrated with pigeons using multiple schedules of response-independent food delivery. In Experiment 1, the introduction of food during a multiple variable-time 30-second variable-time 30-second schedule produced a tenfold increase in activity above the no-food baseline. Each pigeon developed stable differential activity rates during the components (correlated with red and green lights) of a multiple variable-time 30-second extinction schedule. Lengthening the extinction component from 1 to 7 minutes increased the rate differences and produced a reliable pattern of responding during S- (the stimulus correlated with extinction): Activity rate was high immediately following the change from S+ (the stimulus correlated with variable-time 30-second) to S-, then decreased abruptly and remained low throughout the middle of the interval, and subsequently showed a positively accelerated increase until the stimulus changed to S+. In Experiment 2, three pigeons were exposed to a mixed variable-time extinction schedule prior to a multiple variable-time extinction schedule. Auditory rather than visual stimuli were used to determine the generality of Experiment 1 results. The multiple- versus mixed-schedule results indicated that stimulus control of activity occurred for two of the birds, but rate differences between S+ and S- were much less than those demonstrated with visual stimuli. A direct comparison of visual and auditory stimulus control in Experiment 3 supported this conclusion. These parallels between the stimulus control of reinforced responding and that of schedule-induced activity suggest that the stimulus control of induced activity may be a factor in operant stimulus control.

The role of autopecking in behavioral contrast

Four groups of four pigeons each were studied on two different multiple schedules. The cues correlated with the schedule components were localized on the response key for two groups and were not localized for the others. Two groups worked on multiple schedules with variable interval 15-sec in both components, and variable interval 15-sec in one component and extinction in the other. The other two groups had identical procedures except that food was presented on a response-independent variable-time schedule. Variable-interval birds with localized stimuli showed marked behavioral contrast; variable-interval birds with non-localized stimuli showed no behavioral contrast. Variable-time birds with key-light stimuli acquired high rates of autopecking, which changed as treatment changed in a manner that paralleled rate changes, resulting in behavioral contrast for variable-interval birds. Variable-time birds with non-localized stimuli key pecked only at a low rate. The findings indicate that behavioral contrast in pigeons may result from the autopecking that is obtained with stimulus-contingent food presentation.

Contrast and autoshaping in multiple schedules varying reinforcer rate and duration

Thirteen master pigeons were exposed to multiple schedules in which reinforcement frequency (Experiment I) or duration (Experiment II) was varied. In Phases 1 and 3 of Experiment I, the values of the first and second components' random-interval schedules were 33 and 99 seconds, respectively. In Phase 2, these values were 99 seconds for both components. In Experiment II, a random-interval 33-second schedule was associated with each component. During Phases 1 and 3, the first and second components had hopper durations of 7.5 and 2.5 seconds respectively. During Phase 2, both components' hopper durations were 2.5 seconds. In each experiment, positive contrast obtained for about half the master subjects. The rest showed a rate increase in both components (positive induction). Each master subject's key colors and reinforcers were synchronously presented on a response-independent basis to a yoked control. Richer component key-pecking occurred during each experiment's Phases 1 and 3 among half these subjects. However, none responded during the contrast condition (unchanged component of each experiment's Phase 2). From this it is inferred that autoshaping did not contribute to the contrast and induction findings among master birds. Little evidence of local contrast (highest rate at beginning of richer component) was found in any subject. These data show that (a) contrast can occur independently from autoshaping, (b) contrast assays during equal-valued components may produce induction, (c) local contrast in multiple schedules often does not occur, and (d) differential hopper durations can produce autoshaping and contrast.

Autoshaping as a function of prior food presentations

Young chickens were given 1, 10, 100, or 1000 presentations of grain in a hopper. Subsequently, the key was illuminated before each presentation of grain to study autoshaping of the key-peck response. The number of keylight-grain pairings before a bird first pecked the lighted key was found to be a U-shaped function of the number of prior food-only presentations, with pecks occurring significantly sooner after 100 food-only trials than after any of the other values. Two of five chicks at the 100-trial value pecked on the first illumination of the key. Experiment II showed further that when a series of food-only trials (no keylight) preceded keylight-only trials (no food) 30% of the chicks pecked the illuminated key. Experiment III extended the generality of first-trial pecking to pigeons. After preliminary training with food-only, two of five pigeons pecked on the first illumination of a key. The results suggest a close relationship between autoshaping and pseudo-conditioning.

Signalled reinforcement and multiple schedules

The responses of four pigeons were first reinforced in the presence of two different wave-lengths (green and red) on a two-ply multiple schedule with identical variable-interval 3-min schedules of reinforcement associated with each component. While the constant-component reinforcement schedule remained unchanged during the experiment, the schedule associated with the variable component was changed to (1) signalled variable time, (2) unsignalled variable time, or (3) signalled variable interval. The probability with which the availability of the reinforcer was signalled in the variable-interval schedules was either 0.5 or 1.0. Positive contrast occurred in both signalled variable-interval and variable-time schedules, but only when the availability of all the variable-component reinforcers was signalled. Signalling the availability of only 50% of the reinforcers in signalled variable-interval schedules resulted in negative induction. The present data suggest that positive behavioral contrast resulting from signalled reinforcer availability is due to the presence of an extinction-correlated stimulus.

Temporal generalization accounts for response resurgence in the peak procedure

The peak interval (PI) procedure is commonly used to evaluate animals' ability to produce timed intervals. It consists of presenting fixed interval (FI) schedules in which some of the trials are replaced by extended non-reinforced trials. Responding will often resume (resurge) at the end of the non-reinforced trials unless precautions are taken to prevent it. Response resurgence was replicated in rats and pigeons. Variation of the durations of the FI and the non-reinforced probe trials showed it to be dependent on the time when reinforcement is expected. Timing of both the normal time to reinforcement, and the subsequent time to reinforcement during the probe trials followed Weber's law. A quantitative model of resurgence is described, suggesting how animals respond to the signaling properties of reinforcement omission. Model results were simulated using a stochastic binary counter.

The influence of "preparedness" on autoshaping, schedule performance, and choice

Two groups of experimentally naive pigeons were exposed to an autoshaping procedure in which the response key was mounted on the wall (the conventional location) or on the floor of the chamber. In two experiments, subjects readily responded to the wall key, but floor-key subjects required shaping. A subsequent experiment compared performance of wall- and floor-key groups on an ascending series of fixed-ratio schedule values, resistance to extinction, differential reinforcement of other behavior, and reversal of key assignment. Each experiment was followed by several sessions of fixed-ratio training; the performance of the wall- and floor-key groups was almost identical throughout. In the final experiment, a fixed-ratio requirement could be completed on either or both keys. Birds initially chose the key on which they had responded during the preceding (reversal of key assignment) experiment. However, within a few sessions both groups showed almost exclusive preference for the floor key. Preference for a key located on the floor may follow from the fact that pigeons are ground feeders and may thus be more "prepared" to peck the floor than to peck a wall. However, autoshaping, under the conditions prevailing here, occurred much more readily to the wall key, suggesting that pecking a vertical surface is more highly prepared. Difficulties in determining relative preparedness seem moot, however, given the lack of between-group differences in the intervening experiments. It is thus unlikely that schedule performances critically depend upon the specific operant response involved.

The autoshaping procedure as a residual block clock

In the first experiment, 4 pigeons were each presented with a recurring sequence of four key colors followed by the delivery of grain (block clock). Once the rate of pecking had stabilized, three of the colors were replaced, during different series of sessions, by a darkening of the key. The rate of pecking was reduced within those segments of the interval between deliveries of food during which the key was dark; when the key was dark during the final portion of the interval, rates were reduced throughout the entire interval. In the second experiment, 3 new pigeons were exposed to a different sequence of colors, and the final stimulus was replaced in successive conditions by a novel color, a darkened key, and a restoration of the original color. The data indicated that darkening the key had a more severe, more extensive, and more persistent effect than did a mere change in color. These results suggest that it may be fruitful to conceptualize the autoshaping procedure as a special version of the block clock in which pecking is suppressed throughout the greater part of the interval by darkening the key. In the final condition, the same stimulus appeared in each of the last three portions of the interval. The rate of pecking was lower during the last two portions than when distinctive colors were presented, with the peak rate now appearing in the fifth of seven equal temporal components.