Aversives

Aversives are unpleasant stimuli which induce changes in behavior through punishment; by applying an aversive immediately following a behavior, the likelihood of the behavior occurring in the future is reduced. Aversives can vary from being slightly unpleasant or irritating (such as a disliked color) to physically damaging (such as an electric shock). It is not the level of unpleasantness, but rather the effectiveness the unpleasant event has on changing behavior that defines the aversive.

Types of aversive stimuli
There are two types of aversive stimuli:

Unconditioned aversive stimuli
Unconditioned aversive stimuli naturally result in pain or discomfort and are often associated with biologically harmful or damaging substances or events. Examples include extreme heat or cold, bitter flavors, electric shocks, loud noises and pain. Aversives can be applied naturally (such as touching a hot stove) or in a contrived manner (such as during torture or behavior modification).

Conditioned aversive stimuli
A conditioned aversive stimulus is an initially neutral stimulus that becomes aversive after repeated pairing with an unconditioned aversive stimulus. This type of stimulus would include consequences such as verbal warnings, gestures or even the sight of an individual who is disliked.

Use in ABA
Aversives can be used as punishment during applied behavior analysis with autistic children to reduce unwanted behavior such as stimming or self-injury. Aversive stimuli may also be used as negative reinforcement to increase the rate or probability of a behavior when it is removed. Early iterations of the Lovaas technique incorporated significant amounts of aversives during therapy, though the use of aversives in ABA was not without controversey. Lovaas has since stated his disdain for the use of aversives. Contemporary uses of ABA therapy rely on aversives in limited cases, such as when a behavior is dangerous or the reinforcement contingencies that support a behavior are unknown.

The use of aversive procedures and punishment procedures, is one of the primary reasons that the public needs protection by licensing behavior analysis. Through licensure families and consumers will have a regulatory board to turn to in case of dispute. These issues become the core of discussion for practioners ( see Professional practice of behavior analysis). Several National and International Disability Rights Groups have spoken against the use of Aversive Therapies, including TASH and AUTCOM.