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Jennifer Porter
Department of Psychological and Brain Sciences

Last modified: Tuesday, October 30, 2007

Indiana University's William Timberlake honored by Pavlovian Society

Oct. 30, 2007

William Timberlake

William Timberlake

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BLOOMINGTON, Ind. -- The study of Pavlovian conditioning calls to mind dogs automatically salivating to a ringing bell that predicts food. An Indiana University Bloomington researcher is taking a deeper look at the contribution of the natural history and social behaviors of the subjects in Pavlovian conditioning procedures.

William Timberlake, professor in the Department of Psychological and Brain Sciences, recently was presented with the Pavlovian Research Award by the Pavlovian Society. Timberlake received the award at the society's annual meeting in October in Austin, Texas. It was awarded "in recognition of seminal and creative contributions to understanding Pavlovian conditioning in the broader behavioral and ecological context of living organisms."

Timberlake and his students studied the conditioned behaviors of rats and hamsters when presented with social stimulus that predicted the delivery of food. Timberlake proposed that the outcomes of these studies could be predicted from natural history and evolution expressed in the feeding systems of rats and hamsters.

In some studies, a subject rat was briefly exposed to a stimulus rat preceding the delivery of food. Instead of attacking or ignoring the stimulus rat, the subject rat began to approach and engage it socially until the food appeared. The same effect did not occur when a juvenile rat was the predictive stimulus or when a hamster was exposed to a predictive hamster.

"Rats are social feeders," Timberlake said. "They have been selected to learn what foods are safe based on tastes in their mother's milk, and by approaching feeding adults to smell food odors on their breath and sample the food. In contrast, most hamster species are solitary feeders not selected to share food information."

In another series of studies, he and his students examined the reactions of seven rodent species to a rolling ball bearing that predicted the delivery of food. They found that the frequency with which a species interacted with the predictive bearing depended on the extent to which the natural history of the species involved feeding on insects. The rodents from insect-eating species, despite never seeing an insect, tracked and interacted with the rolling bearing, while rodents from plant and seed-eating species ignored the bearing or used it as a signal to go to the food tray. Also, among insect-eating rodents, the form of interaction with the bearing was related to the form of their species-typical predatory reactions to moving prey.

Timberlake's subsequent work in Pavlovian conditioning has focused on dividing the interval between food presentations into two main search states: General search, which controls behavior related to searching more widely for food; and Focal search, which controls behavior focused on the capture of a particular item.

"Short predictive stimuli are assumed to condition primarily a focal search state and focused search behaviors," he said. "Longer predictive stimuli are assumed also to condition a general search state expressed in locomotor behaviors."

The results explain why Pavlovian conditioning has been primarily assumed to occur over short temporal intervals between predictive stimuli and responses, and why it was necessary to measure different responses to see conditioning at longer temporal intervals, Timberlake said.

The Pavlovian Society, established in 1955 by W. Horsley Gantt at the Johns Hopkins School of Medicine, is dedicated to the scientific study of behavior and promotion of interdisciplinary scientific communication. For more information, visit