Aversives

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Aversives are negative stimuli which induce behavior changes. Aversives can be powerful motivators for behavioral change, for example, the proverbial hot stove which cats and children learn to avoid after no more than a couple of experiences. Averives can also be only moderately unpleasant, like the bad song on the radio that causes the listener to change the channel. It is not the level of unpleasantness, but rather the effectiveness the unpleasant event has on changing behavior that defines the aversive.

Aversives are used as part of the Applied Behavior Analysis model, and are considered a type of punishment, since they decrease the rate or probability of the behavior they follow. An aversive stimulus may also increase the rate or probability of a behavior when it is removed as a consequence, and in this way it can function as negative reinforcement (Alberto, 2003). The perfect example is the alarm clock. The ringing of the clock is aversive for most people which motivates them to wake and hit the off button. The cessation of the ring reinforces the behaviors of waking up and hitting the button, making the person more likely to behave in the same way the next time they are presented with the annoying ringing.

There are two types of aversive stimuli: unconditioned aversive stimuli and conditioned aversive stimuli.

Unconditioned aversive stimuli naturally result in pain or discomfort. Included in this category are naturally occurring consequences, such as contact with a hot stove, and contrived consequences, such as the use of electric shock. Unconditioned aversive stimuli also include consequences that are considered mild aversives such as administering distasteful substances (lemon juice, water, and ammonia), and the use of physical control or restraint.

A conditioned aversive stimulus is an initially nuetral stimulus that becomes aversive after repeated pairing with an unconditioned aversive stimulus. This type of stimulus would include consequences such as verbal warnings, vocal tones, or gestures. For example, if a child is bitten by a dog after the dog growls at him, he may learn to pair the nuetral stimulus (growling) with the unconditioned aversive (the painful dog bite), causing that growling sound to cause him some of the pain and fear of a dog bite the next time he hears it, possibly without ever again being paired with the painful bite.