Methods to Extinguish Classically Conditioned Fear Responses


Classical conditional is most often referenced with regard to Pavlov’s experiments with animals learned responses to unconditioned stimuli.  All things being equal, pairing of two stimuli creates an associated response to both.  For instance, a neutral stimulus is presented which creates neither a positive nor negative reaction on behalf of the participant.  Subsequently, a second stimulus known as the unconditioned stimulus is presented which receives a positive or negative reaction from the participant.  This scenario results in the neutral stimulus becoming a conditioned stimulus such that frequent pairings of these stimuli results in the originally neutral stimulus evoking the same reaction from the participant as the unconditioned stimulus.  For example, frequent pairing of a neutral tone with a foot shock will result in a physiological response to the tone as if it were also the negative stimulus of a foot shock.

It may be noted I used the phrase “all things being equal” because all stimuli are not created equal and neither are individuals.  For instance, it may take several pairings to create a conditioned response to the sound of a tone.  However, conditioned responses are known to occur far more quickly when involving traumatic or excessively painful events.  For example, I have previously been involved in a car accident.  Upon arriving at the location where the accident occurred on a different day, I would feel anxious and hyperaware.  This feeling could be a conditioned response (anxiety and fear) to the location where the accident or unconditioned stimulus (accident) was initially elicited.  I have noticed, however, that after driving to the same location on many occasions following the accident, eventually I stopped feeling anxious and fearful at that intersection.  This is known as extinction of the conditioned response.

Extinguishing a naturally occurring conditioned response may prove especially difficult predominantly because humans are prone to avoid situations that make them feel uncomfortable or cause them pain (Friedman & Schustack, 2012).  As an example, my son ate a corndog for lunch at preschool.  A few hours later he vomited.  After that day he refused to eat corndogs.  It has been six years since that event occurred; however, he will still not eat a corndog.  Eating a corndog is entirely voluntary and certainly not an issue I felt required intervention action because he did not generalize his discomfort to all fast food or any food that had bread around it.  If he had refused to eat hamburgers or hotdogs in general, then I may have been more likely to push him to eat a corndog so he would realize that his vomiting event had not been caused by the corndog.

Conditioned responses can also be positive.  For instance, a neutral stimulus may become paired with an unconditionally positive stimulus so that in the future the neutral stimulus is deemed rewarding or pleasurable.  Unfortunately, many addictions can result from these types of pairings.  Recently, I went to Las Vegas with my family.  Many of the slot machines are designed to produce vibrant, memorable sounds and/or sounds.  Should a person win some amount of money and hear a particular sound at that time, it is possible that the person will come to associate the sound with winning money.  In this way, many people come to enjoy gambling and/or playing the slots.  In fact, the fact that slot machines and other types of gambling only provide partial reinforcement or rewards only occurs some of the time actually increases the persistence of the conditioned response.  As mentioned previously, extinction occurs if the conditioned stimulus is presented, but the unconditioned response does not occur.  If I gamble for days and days and never win anything, no matter how many times the slots make vibrant sounds and lights, I will eventually stop expecting a payout.  However, conditioned responses also experience periodic spontaneous recovery.  This means that occasionally I might hear a bell or see a light and again expect a payout.  Should that payout happen to occur, the conditioned response will become even stronger.

Another method utilized to evoke extinction involves desensitization whereby the individual is slowly reexposed to the conditioned stimulus.  This procedure is used for treatment of phobias, such as fear of heights or dogs.

Another method utilized to evoke extinction that seems to be producing more effective results than simple extinction is purposeful disassociation of the paired stimuli (Mickley et al., 2009).  For instance, Mickley, et al. (2009) created a conditioned response in rats to a novel taste.  Thereafter, they divided the rats into an extinction only group and an explicitly unpaired group.  In the explicitly-unpaired group the rats alternated exposure to the neutral stimulus (extinction) to exposure of unconditioned stimulus (nausea) without neutral stimulus, on different days.  The results revealed that not only did the explicitly unpaired group exhibit extinction more quickly than the extinction-only group, but they also did not exhibit any spontaneous recovery effects.

The results of this research is especially meaningful because it suggests yet another avenue of treatment to reduce conditioned responses.  However, the application to human subjects may be somewhat more difficult because it would be unethical to expose a person to alternate exposure of a conditioned stimulus with an unconditioned stimulus that produces physically, mentally, or emotionally harmful responses.



Friedman, H. S., & Schustack, M. W. (2012). Personality: Classic theories and modern research (5th ed.). Boston, MA: Allyn & Bacon.

Mickley, G. A., DiSorbo, A., Wilson, G. N., Huffman, J., Bacik, S., Hoxha, Z., Kim, Y. (2009). Explicit disassociation of a conditioned stimulus and unconditioned stimulus during extinction training reduces both time to asymptotic extinction and spontaneous recovery of a conditioned taste aversion. Learning and Motivation, 40(2), 209-220. 10.1016/j.lmot.2009.01.001


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