Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)



Committee Chair(s)

Carl D. Cheney


Carl D. Cheney


Grayson Osborne


In four experiments, pigeons performed on schedules of food reinforcement across two different contexts. One context consisted of having the operant chamber fully illuminated, with increased noise levels, and reflective aluminum foil draped over the chamber sidewalls. This context was paired with oral injections of water. Another context consisting of having the chamber dark except for response keylight and at ambient noise levels was paired with oral injections of ethanol. Ethanol dosages were determined by using a dose that doubled the average variable-ratio postreinforcement pause. These procedures established the dark context as a conditioned stimulus capable of producing Pavlovian conditioned tolerance to ethanol. This tolerance was expected to be context specific to the dark context.

At the same time the reinforcement schedule produced a learned compensation or tolerance for the ethanol that would not be limited to one context. Tolerance was defined here in behavioral terms: a variable-ratio (VR) schedule of reinforcement with high rates of responding and little or no pausing after food delivery, similar to behavior following water delivery but in this case, after ethanol delivery.

To test the efficacy of the context specific tolerance relative to the reinforcement-schedule-acquired-tolerance, probes were conducted. These consisted of delivering ethanol while the context predicted water.

The results indicated that most subjects displayed tolerance that was not context specific. However, for a minority of subjects, the acquired respondent tolerance was highly context specific, being present only in ethanol paired context. In explanation, those subjects who displayed context specific tolerance also tended to have more behavioral disruption from smaller doses of ethanol than other subjects. This subset of subjects showed more sensitivity to ethanol. At the higher doses, Pavlovian tolerance may have been hindered by the prolonged systemic effects of the ethanol. The same dosages allowed for more intoxicated practice and enhanced the learned tolerance from the reinforcement schedule.

The implications of this research point to additional studies of how and why tolerance to the behavioral effects of a drug is acquired.