What Is a Taste Aversion?

Conditioned taste aversions can lead to food avoidance
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Have you ever gotten ill after eating something and later found that just the thought of that food made you feel a bit queasy? This is a great example of what is often referred to as a conditioned taste aversion. A conditioned taste aversion can occur when eating a substance is followed by illness. For example, if you ate a taco for lunch and then became ill, you might avoid eating tacos in the future even if the food you ate had no relationship to your illness.

While it might seem expected that we would avoid foods that were immediately followed by illness, research has shown that the consumption of the food and the onset of the illness do not need to necessarily occur close together. Conditioned taste aversions can develop even when there is a long delay between the neutral stimulus (eating the food) and the unconditioned stimulus (feeling sick).

In classical conditioning, conditioned food aversions are examples of single-trial learning. It requires only one pairing of the previously neutral stimulus and the unconditioned stimulus to establish and automatic response.

Examples of Taste Aversions

Imagine that you are on vacation and eat a chicken enchilada at a restaurant. Hours after eating the enchilada, you become violently ill. For years after that incident, you might be unable to bring yourself to eat a chicken enchilada and may even feet queasy when you smell foods that remind you of that particular dish.

This conditioned taste aversion can occur even when you know that your illness is not connected to eating that particular item. In reality, you might be fully aware that you picked up a nasty stomach virus from one of your traveling companions who had been ill just days before the trip.

These conditioned taste aversions are quite common and can last for days to several years.

Consider your own aversions to certain foods. Can you link your distaste for particular items to a period of illness, queasiness or nausea? People may find that they avoid very specific types of food for years simply because they consumed that particular item before they became ill.

Understanding Taste Aversions

Can taste aversions occur both consciously and unconsciously? In many cases, people may be completely unaware of the underlying reasons for their dislike of a type of food. Why do these taste aversions occur, especially when we consciously realize that the illness was not tied to a particular food?

As you may have already realized, conditioned taste aversions are a great example of some of the fundamental mechanics of classical conditioning. The previously neutral stimulus (the food) is paired with an unconditioned stimulus (an illness), which leads to an unconditioned response (feeling sick). After this one-time pairing, the previously neutral stimulus (the food) is now a conditioned stimulus that elicits a conditioned response (avoiding the food).

Is that all there is to these conditioned taste aversions? As you may have already noticed, the scenario described above does not exactly fit with the standard expectations for classical conditioning. First of all, the conditioning occurred after just a single pairing of the neutral stimulus and unconditioned stimulus (UCS). As you may also remember from your studies of classical conditioning, the time span between the neutral stimulus and UCS is usually just a matter of seconds. In the case of a conditioned taste aversion, the time lapse often amounts to several hours.

While it may seem to violate the general principles of classical conditioning, researchers have been able to demonstrate the effects of conditioned taste aversions in experimental settings. In one such experiment, psychologist John Garcia fed flavored water (a previously neutral stimulus) to lab rats. Several hours later, the rats were injected with a substance (the UCS) that made them ill. Later, when the rats were offered the flavored water, they refused to drink it.

Explaining Conditioned Taste Aversions

Because Garcia’s research contradicted much of what was previously understood about classical conditioning, many psychologists were unconvinced by the results. Pavlov had suggested that any neutral stimulus could elicit a conditioned response. If that were true, then why would the feelings of sickness be associated with the food that was eaten hours earlier? Wouldn't the illness be associated with something that had happened right before the symptoms occurred?

What Garcia and other researchers were able to demonstrate was that in some cases, the type of neutral stimulus used does have an influence on the conditioning process. So why does the type of stimulus matter so much in this particular case? One part of the explanation lies in the concept of biological preparedness. Essentially, virtually every organism is biologically predisposed to create certain associations between certain stimuli. If an animal eats food and then becomes ill, it might be very important to the animal's continued existence to avoid such foods in the future. These associations are frequently essential for survival, so it is no wonder they form easily.

Sources

Garcia, J., Ervin, F.R., & Koelling, R.A. Learning with prolonged delay of reinforcement. Psychonomic Science, 1966; 5: 121-122.

Garcia, J. & Koelling, R.A. Relation of cue to consequence in avoidance learning. Psychonomic Science, 1966; 4: 123-124.

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