Decreased Key Pecking in Response to Reward Uncertainty and Surprising Delay Extension in Pigeons

The Pavlovian autoshaping paradigm has often been used to assess the behavioral effects of reward omission on behavior. We trained pigeons to receive a food reward (unconditioned stimulus or UCS) following illumination of a response key (conditioned stimulus or CS). In Experiment 1, one group of pigeons was trained with two 100% predictive CS-UCS associations (reward certainty) and another group with two 25% predictive CS-UCS associations (reward uncertainty) for 12 sessions. In both groups, the two CS durations were 8 s. Then, in each group, the duration of one CS remained unchanged and that of the other CS was suddenly extended from 8 to 24 s for 6 sessions. In Experiment 2, some experienced individuals (from Experiment 1) and naïve individuals formed two groups trained with a 24-s CS throughout for 18 sessions. Our results show that pigeons (a) pecked less at the uncertain than the certain CS, (b) decreased and then increased CS-pecking after extending CS duration, especially in the certainty condition, (c) were unresponsive to the 24-s CS in the absence of previous experience, and (d) decreased their response rate close to the end of a trial irrespective of the reinforcement condition, CS duration, and amount of training. These results are discussed in relation to several theoretical frameworks.

Behavioral Psychology’s Matching Law Describes the Allocation of Covert Attention: A Choice Rule for the Mind

The matching law describes the allocation of behavior over a wide range of settings, including laboratory experimental chambers, forest foraging patches, sports arenas, and board games. Interestingly, matching persists in settings in which economic analyses predict quite different distributions of behavior (and it also differs systematically from “probability matching”). We tested whether the matching law also describes the allocation of covert cognitive processes. Sixty-four participants viewed two, small, vertically arranged adjacent stimuli that projected an image that fit within the fovea. A trial-version of the reward contingencies used in matching law experiments determined which stimulus was the target. The amount of time the stimuli were available was tailored to each subject so that they were not able to make use of the information in both stimuli even though an eye-tracking experiment confirmed that they saw both. The implication of this restriction is that subjects had to decide which stimulus to attend to prior to each trial. The only available objective basis for this decision was the relative frequencies that a stimulus was the target. Although shifts in attention were covert, and the procedure did not provide explicit reinforcers, the matching law equation described the division of attention between two small, briefly presented stimuli as accurately as it describes the allocation of key pecking between two illuminated disks in hungry pigeons.

On the role of responses in Pavlovian acquisition

A defining feature of Pavlovian conditioning is that the unconditioned stimulus (US) is delivered whether or not the animal performs a conditioned response (CR). This has lead to the question: Does CR performance play any role in learning? Between the 1930's and 1970's, a consensus emerged that CR acquisition is driven by CS-US experiences, and that CRs play a minimal role, if any. Here we revisit the question and present two new quantitative methods to evaluate whether CRs influence the course of learning. Our results suggest that CRs play an important role in Pavlovian acquisition, in such paradigms as rabbit eyeblink conditioning, pigeon autoshaped key pecking, and rat autoshaped lever pressing and magazine entry.

Social learning and facilitation of operant key-pecking by domestic hens

It has been suggested that feather pecking becomes widespread in groups of birds because it is socially learnt. However, a bird pecking the feathers of another seldom gains obvious extrinsic reinforcement for this behaviour (the feather is not always eaten, or material pecked from the plumage). Two aspects of social learning that have received little attention are whether reinforcement of the bird performing the behaviour (the demonstrator) is required for the watching bird (the observer) to learn, and in addition, whether single or multiple exposures to the behaviour are required. In two experiments we used a model behaviour - operant key pecking - to examine the effects of reinforcement of demonstrators (experiment 1) and the effectiveness of repeated demonstrations (experiment 2) on social learning by domestic hens.

The effect of demonstrator reward on social learning of operant key pecking by domestic hens

Social learning is said to occur when social interaction facilitates the acquisition of a novel pattern of behaviour. It usually takes the form of an experienced animal (the demonstrator) performing a behaviour such that a naive animal (the observer) subsequently expresses the same novel behaviour, earlier or more completely than it would have done using individual learning. Social learning is involved in the transmission of a great variety of behaviours, e.g. tool-use, food preferences, and has also been implicated in maladaptive behaviours such as stereotypies in voles. In studies of social learning, the observers usually see the demonstrators receive a reward for performing the required behaviour. But, the role of the reward has rarely been investigated and results have been equivocal. Understanding the role of demonstrator reward on social learning is necessary to assess the cognitive abilities of individuals of different species, and aids understanding of the transmission of maladaptive behaviours.