54 Classically Conditioned Drug Tolerance

Based on Research by Shepard Siegel, Ph.D.. Psychology Science Minute written by Juanita N. Baker, Ph.D..

Have you ever wondered why on the news so often a person dies from a drug overdose?  Our bodies are constantly trying to achieve homeostasis. When presented with environmental cues (like the bed, syringe, opening the powder paper) that a drug is going to be taken, the body starts physiological counter measures to try to protect itself.  However, over a number of occasions the body adjusts, requiring a higher dose to have the same buzz effect, thus causing drug tolerance.

In a psychological experiment, Shepard Siegel and colleagues demonstrated that rats can also become  drug tolerant, making these physiological changes when expecting heroin injections repeatedly given in one setting but not in another setting where sugar solution injections were given.  Next, all drug-addicted rats received a larger-than-usual dose; half in the usual setting where drugs were given and half where previously only sugar injections were given.  Twice as many rats, 64%, died in the sugar setting compared to 32% in the heroin setting!

You know the dangers of addictive drugs, but there is an additional danger.  Caution!  Your body may not be prepared to handle its usual dose in a new setting, as the old setting cues aren’t there to allow it to prepare for the dose.


Siegel, S. (1984).  Pavlovian conditioning and heroin overdoes: Reports by overdose victims.  Bulletin of the Psychonomic Society, 22, 428-430.

Siegel, S., Hinson, R.E., Krank, M.D., & McCully, J. (1982). Heroin “overdose” death: The contribution of drug-associated environmental cues.  Science, 216, 436-437.

Further information:

Technical explanation of this research:  Respondent Conditioning (Pavlovian Conditioning or Classical Conditioning):  is the demonstrated phenomena that the body learns automatically to respond to associated environmental cues in anticipation of a reinforcement (pleasurable event, food, drug).  This principle is operating in Shepard Siegel’s experiment.  The environmental cues that originally did not elicit any response became conditioned or were learned to precede the pleasurable event and thus elicited an accommodation response by the body because the cues were associated with the drug effects that did originally elicit the body’s pleasurable response.

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