Conditioned Pecking Research Articles

Blocking NMDA-Receptors in the Pigeon's Medial Striatum Impairs Extinction Acquisition and Induces a Motoric Disinhibition in an Appetitive Classical Conditioning Paradigm.

The medial striatum of birds resembles the mammalian dorsal striatum, which plays a key role in the extinction of learned behavior. To uncover the variant and invariant neural properties of extinction learning across species, we use pigeons as an animal model in an appetitive extinction paradigm. Here, we targeted a medial sub-region of the pigeon’s striatum that receives executive, visual and motor pallial projections. By locally antagonizing the N-methyl-D-aspartate (NMDA) receptors through 2-Amino-5-phosphonovalerianacid (APV) during extinction, we observed an unspecific disinhibition effect, namely an increase in conditioned pecking to a rewarded control stimulus. In addition, blocking the NMDA receptors substantially deteriorated the extinction acquisition, implying that the pigeons still responded vigorously to the CS- even without food reward during extinction. After correcting for the unspecific effect of APV, the impaired extinction acquisition remained significant, which leads to the assumption that the delayed extinction effect is possibly caused by deficits in the updating of value coding of altered reward contingencies. Also, the APV-induced disinhibition seems to result from local hyperactivity that primarily drives actions towards cues of high appetitive value. The overall correspondence of our results with those from mammals suggests common neural substrates of extinction and highlights the shared functionality of the avian and mammalian dorsal striatum despite 300 million years of independent evolution.

Long-term behavioral sensitization to apomorphine is independent of conditioning and increases conditioned pecking, but not preference, in pigeons

When rodents are given a free choice between a variable option and a constant option, they may prefer variability. This preference is even sometimes increased following repeated administration of a dopamine agonist. The present study was the first to examine preference for variability under the systemic administration of a dopamine agonist, apomorphine (Apo), in birds. Experiment 1 tested the drug-free preference and the propensity to choose of pigeons for a constant over a variable delay. It appeared that they preferred and decided more quickly to peck at the optimal delay option. Experiment 2 assessed the effects of a repeated injection of Apo on delay preference, in comparison with previous control tests within the same individuals. Apo treatment might have decreased the number of pecks at the constant option across the different experimental phases, but failed to induce a preference for the variable option. In Experiment 3, two groups of pigeons (Apo-sensitized and saline) were used in order to avoid inhomogeneity in treatments. They had to choose between a 50% probability option and a 5-s delay option. Conditioned pecking and the propensity to choose were higher in the Apo-sensitized pigeons, but, in each group, the pigeons showed indifference between the two options. This experiment also showed that long-term behavioral sensitization to Apo can occur independently of a conditioning process. These results suggest that Apo sensitization can enhance the attractiveness of conditioned cues, while having no effect on the development of a preference for variable-delay and probabilistic schedules of reinforcement.

Midsession shifts in reward probability and the control of behavioral variability.

Extensive research has shown that the variability of organismal behavior is great when contingent reinforcement is delayed, small, or improbable. This research has generally employed stable response-reinforcer relationships, and therefore is limited in its explanatory scope with respect to a dynamic environment. We conducted two experiments to investigate whether pigeons' conditioned pecking behavior shows anticipatory or perseverative patterns of behavioral variability when the reinforcement probability reliably changes within experimental sessions. In Experiment 1, three pigeons received alternating sessions in which the reinforcement probability (35% or 4.2%) was shifted at the midpoint of each session in the presence of the same discrete cue. Experiment 2 featured a similar design, but with the inclusion of a discrete visual cue that changed at the session midpoint, and thus unambiguously indicated reinforcement probability. Local reinforcement rates only reliably controlled response variability when a discrete visual cue was available. Without this, pigeons did not discriminate between trial types in the first halves of sessions, and showed evidence of perseveration of response variability following a within-session shift. Critically, this is the first experimental demonstration that the relationship between reinforcement probability and behavioral variability is moderated by another factor (i.e., trial position within a session). This study thus expands our understanding of the control of behavioral variability as a function of experiential factors.

Sensitization to apomorphine, effects of dizocilpine NMDA receptor blockades

The dopamine agonist apomorphine (apo) elicits bouts of stereotyped pecking in pigeons, a response which increases with successive apo injections. This sensitization is strongly context-specific and has been suggested to arise through a Pavlovian conditioning to both external and internal cues. We hypothetized that this learning involves dopamino–glutamatergic interactions and investigated the issue by inducing NMDA glutamate receptor blockades with the antagonist dizocilpine (diz). A first experiment examined the effects that four different doses (ranging between 0.05 and 0.12 mg/kg) of diz co-administered with a standard dose of 0.5 mg/kg of apo had on the development of the incremented response and on the later expression of the conditioned pecking response. Both responses were impaired by doses of around 0.10 mg/kg diz. A second experiment assessed whether either a diz treatment or a diz plus apo co-treatment affected the development of a subsequent sensitization to apo. The first treatment had no effect on the latter sensitization. A part sensitization that arose with the second treatment did not transfer to the final sensitization. The last experiment examined whether the administration of diz had an immediate effect on the incremented responding to apo and on the conditioned response shown by already sensitized pigeons. No effect was apparent with the first treatment, but there was a marked response inhibition with the second treatment. It is concluded that NMDA glutamate receptors play an important role in apo-induced sensitization in pigeons which is compatible with the Pavlovian conditioning account of sensitization.

Sensitization to apomorphine in pigeons is due to conditioning, subject to generalization but resistant to extinction.

Apomorphine (Apo) administration induces a persistent bout of pecking in pigeons and other birds. Repeated injections of Apo in pigeons lead to sensitization, i.e. the pecking response to a particular dose increases up to a dose-dependent asymptotic level. It is also known that Apo-induced pecking can be classically conditioned to the cage environment where the animals experience the effect of the drug. Here we address the question of whether, and to what extent, the sensitization effect arises as a consequence of a conditioning or of a pharmacological process. An extinction experiment demonstrated that an extinction procedure supposed to be effective in inhibiting the conditioned pecking response was not effective in suppressing the sensitization to Apo, thus casting provisional doubt on the conditioning hypothesis. However, a conditioning experiment demonstrated that the sensitization effect undoubtedly involved an important component of conditioning to an experimental cage environment, but also suggested that there was an additional component possibly not due to learning. A generalization experiment, however, showed that this second component was very probably due to a stimulus generalization effect deriving from conditioning to the home cage, suggesting that learning can account for most, if not all, of the increase in Apo-induced pecking and that an exclusively pharmacological sensitization process plays, at best, a minor role. The apparent contrast between the results of the first experiment, indicating that the sensitization is not affected by inhibitory conditioning, and the results of the last two experiments, suggesting that the sensitization is due to excitatory conditioning, can be resolved by assuming that Apo induces a drug-state-dependent conditioning. These results are related to findings and arguments concerning the sensitization to psychostimulant drugs in mammals.

Trigeminal deafferentation and conditioned pecking in pigeons

To clarify the contribution of peripheral trigeminal input to the control of pecking behavior we examined head and jaw movement kinematics and peck localization in pigeons with surgical section of trigeminal nerves providing somatosensory input to the beak. Conditioning procedures were used to bring the pecking/grasping components of pecking under the control of a visual target. Conditioned head and jaw movements were monitored `on-line' using movement transducers and terminal peck location was recorded using `touch-screen' technology. The periodic delivery of a food reinforcer provided repeated opportunities to monitor the kinematics of ingestive pecks. Deafferentation produced deficits in mandibulation during ingestive pecking and in the coordination of head and jaw movements during conditioned pecking. These results are attributed to disruptions in trigeminal feedback and feedforward mechanisms, respectively. In contrast with previous studies, deafferentation did not impair the precision of peck localization. Possible reasons for the absence of localization deficits are presented. The results are discussed in relation to the role of peripheral inputs in the control of prehensile movements.

Conditioned `prehension' in the pigeon: kinematics, coordination and stimulus control of the pecking response

Like human prehensile behavior, the pigeon's ingestive pecking response is elicited by visual stimuli conveying information about the location and size of the target. This information is used to generate localized ingestive pecks whose gapes are amplitude-scaled to seed size, prior to contact. We employed high-resolution, `real-time' monitoring of head acceleration, jaw movements and terminal peck location to examine the kinematics, coordination and stimulus control of conditioned pecking. Conditioning procedures were used to bring pecking under the control of visual targets whose stimulus properties (size, location) were independently varied, while simultaneously monitoring pecking response parameters. Stimulus control of the transport component (peck localization) is extremely precise, even in the absence of a specific localization-dependent reinforcement contingency. Subjects also showed amplitude-scaling of gape size to the size of a visual target, but over a more restricted range than shown to food pellets of comparable sizes. Comparison of the kinematic profiles of conditioned and ingestive pecks suggests that conditioned pecking is functionally analogous to human `pointing' rather than `grasping' behavior.

Behavioral morphology of the pigeon's peck: ingestion, prehension and cognition.

In nature, pecking involves the transport of a prehensile effector organ (the beak) towards biologically significant targets, and the generation jaw movement patterns whose probability and topography are appropriate to the stimulus properties of the target (e.g., distance, direction, size) and the motivational state of the animals (hunger, thirst). Because conditioned pecking preserves essential topographic features of the ingestive peck, we have used the pigeon's conditioned pecking response as a "model system" for the study of motor control, response form modulation and cognitive processes. In the first study, conditioning procedures were used to bring pecking under the control of visual targets whose stimulus properties (size, location) were independently varied, while simultaneously monitoring head acceleration, jaw movements and terminal peck location. Comparison of the kinematic profiles of conditioned and ingestive pecks suggests that conditioned pecking is functionally analogous to human "pointing" rather than "grasping" behavior. In the second study, we manipulated reinforcer type and size to generate populations of "virtual" eating and drinking responses and used them to study the process of response form modulation. The data suggest that different response forms do not reflect "fixed" movement patterns but the modulation of movement patterns across a topographic continuum. In the third study we manipulated stimulus, response and deprivational variables to test a cognitive model for the study of "expectancy", "intention", and "choice" in pigeon.

Sensitization to apomorphine in pigeons: unaffected by latent inhibition but still due to classical conditioning.

When administered apomorphine, pigeons exhibit protracted bouts of pecking behavior. This response is subject to sensitization, as it initially increases with repeated drug injections. The hypothesis is examined that the sensitization is due to a Pavlovian conditioning of the drug-induced pecking to the environment in which it first takes effect. In a first experiment, we attempted to suppress this conditioning by extensively pre-exposing the birds to the test environment and saline injections (latent inhibition procedure). As the experiment yielded undiminished sensitization, it cast doubt on the conditioning hypothesis. However, while inhibitory pretraining also proved ineffective in a second experiment, a shortening of response latencies specific to the environment in which the animals had first experienced the apomorphine effect supported the conditioning hypothesis. It is suggested that the absence of latent inhibition may be due to the interference of a context-dependent conditioning effect. A third experiment that examined the hypothesis that the reinforcing properties of apomorphine might be attributable to its well known anorectic properties. The results provided some support for this notion. At the same time, they also confirmed that apomorphine-induced pecking conditions reliably to environmental cues. These cues are then by themselves capable of provoking conditioned pecking.

Dissecting the conditioned pecking response: an integrated system for the analysis of pecking response parameters.

The conventional pecking response key, although an excellent transducer of response rate, can provide minimal information on the topography, coordination, or localization of conditioned pecking. We describe the hardware and software components of a system that, in addition to recording response rates, permits simultaneous "on-line" monitoring of head acceleration, jaw movement, terminal peck location, and duration of pecking response. Head movements are monitored with a miniature accelerometer, jaw movements with a magnetosensitive transducer, and peck location with modified touch screen technology. Initial experiments with the system suggest that it will be useful in studies of response differentiation, acquisition and maintenance of complex discriminations, and interaction of conditioned and unconditioned stimuli in the control of pecking response probability and response topography.

Engineering Behavior: Project Pigeon, World War II, and the Conditioning of B. F. Skinner

Engineering Behavior: Project Pigeon, World War II, and the Conditioning of B. F. Skinner JAMES H. CAPSHEW During the Second World War the scientific outlook and profes­ sional goals of American psychologist B. F. Skinner underwent a remarkable metamorphosis. Wartime contingencies reshaped his re­ search agenda and converted him to the cause ofbehavioral engineer­ ing. Before the war, Skinner was reluctant to venture very far outside the academic laboratory. He was a scientific purist who resisted extrapolating the results of his animal experimentation to the realm of human behavior. After the war, he attempted to make such connections boldly explicit, arguing that the scientific principles of behaviorism had widespread applicability to human affairs. By the 1950s Skinner had emerged as an advocate of the use of operant conditioning techniques for the control of individual and group behavior in a variety of settings and promoted applications ranging from teaching machines to the design of entire societies. Skinner’s transition from inventive scientist to social inventor can be traced to the circumstances of World War II, which provided him with opportunities to explore the technological ramifications of operant psychology. Years later he noted that three wartime projects had dramatically broadened his intellectual horizons by offering the first evidence that his system of behavioral science could engender a system of behavioral engineering.1 The first was known as Project Dr. Capshew teaches in the Department of History and Philosophy of Science and serves as assistant director of the Program on Scientific Dimensions of Society at Indiana University. He gratefully acknowledges the editorial suggestions of Lau­ rence D. Smith, William R. Woodward, Alejandra C. Laszlo, Eliot Hearst, and B. F. Skinner and the encouragement received from audiences that heard earlier versions of this article at Indiana University and at annual meetings of the Air Force Historical Foundation, the Society for the History of Technology (where he was awarded the 1986 Joan Cahalin Robinson Prize), and the Association for Behavior Analysis. lB. F. Skinner, “My Years at Indiana” (paper prepared March 31, 1988, for Indiana University Department of Psychology Centennial Celebration, Bloomington, April 1988), p. 5; a copy is in the personal collection of the author.© 1993 by the Society for the History of Technology. All rights reserved. 0040-165X/93/3404-0001$01.00 835 836 James H. Capshew Pigeon—an attempt to construct a missile guidance system utilizing the conditioned pecking behavior of pigeons. Project Pigeon con­ sumed much of Skinner’s energy during the war, and, even though it was never brought to fruition, it played a pivotal role in reorienting his thinking toward the possibilities of behavioral engineering.2 The second project was closer to home. Faced with the challenges of raising a second baby daughter, Skinner drew on his manual skills and invented the “baby-tender,” a futuristic climate-controlled crib de­ signed to promote the physical and psychological health of infants.3 Featured in the Ladies’ Home Journal shortly following the war, the device was later marketed commercially with little success as the “Aircrib.”4 Skinner’s third novel project was precisely that—a novel. During the summer of 1945 he drafted the manuscript that would be published three years later as Walden Two.' The book was Skinner’s attempt to conceive a utopian human society based on the principles of reinforcement that he had gleaned from his laboratory research on animal behavior. Taken together, these efforts represent Skinner’s initial forays into the realm of behavioral engineering, and they clearly demonstrate how the technocratic ideals embedded in his research practices found expression in the wartime context. Although Skinner’s work was undeniably idiosyncratic, it reflected broader trends in American psychology that reached their fullest expression during the Second World War, with its overriding emphasis on military utility and the virtues of order, control, and effectiveness.1’ Of the three projects, Walden Two became the most famous. It was the first step in Skinner’s public transformation from experimental psychologist to social philosopher, and its description of an entire culture molded along behaviorist lines suggested the scope of Skin­ ner’s ambitions. As important as the novel was, it was only the most visible manifestation of a more fundamental...

Classical conditioning of jaw movements in the pigeon: Acquisition and response topography

Previous studies have shown (1) that the form of the pigeon’s conditioned keypecking response resembles that of its ingestive pecking response, (2) that both ingestive and conditioned pecking in the pigeon are compound responses, including both transport (neck-movement) and gape (jaw-movement) components, and (3) that during operant conditioning or autoshaping of pecking behavior, the gape component comes under the associative control of the CS. In the present study, the gape component was experimentally isolated and a classical conditioning paradigm (water US) was used to bring jaw movements under the control of a CS (light). The results indicate that the topography of the jaw-movement CR is very similar to, though more variable than, that of the UR. They are consistent with the hypothesis that reported similarities in the form of ingestive and conditioned pecking responses reflect, in part, classical conditioning of the gape component.

Second-order autoshaped key pecking based on an auditory stimulus.

In Experiment 1, pigeons were exposed either to paired or to unpaired presentations of a tone and grain, and then to paired presentations of a keylight with the tone. Substantial second-order conditioned pecking to the keylight was produced in the birds that had received paired presentations of tone and grain. In Experiment 2, second-order pecking to the keylight increased in probability across four groups that had received, respectively, 20, 80, 140, or 200 paired presentations of tone and grain. In Experiment 3, the amount of pecking directed towards a keylight which predicted the first-order, tone CS was as substantial in birds without a prior history of key pecking as in birds with such a history. A further experiment failed to discover any significant differences in the levels of second-order pecking to a keylight paired with a first-order tone CS or with a first-order keylight CS. Thus, an auditory signal that does not itself support pecking may enable a localized visual stimulus to evoke key pecking.

EXTINCTION‐INDUCED AGGRESSION1

Pigeons were conditioned to peck a response key under a procedure that alternated periods of food reinforcement with periods of extinction. The pigeons attacked a nearby pigeon at the onset of extinction. Some also attacked a stuffed model of a pigeon. The duration of attack was an inverse function of the time since the last food reinforcement and a direct function of the number of reinforcements. The pigeons attacked after the last food delivery whether or not the conditioned pecking response was required and whether or not the extinction period was signaled. The food had to be eaten; the mere sight and sound of food being delivered did not produce attack. Prior satiation reduced attack. The phenomenon was not attributable to a past history of competition between pigeons since socially deprived pigeons also attacked. Superstitious reinforcement of attack was not found to be a factor. The results indicated that the transition from food reinforcement to extinction was an aversive event that produced aggression.