Describes a relationship between events in which the rate of a behavior’s occurrence increases when some (usually aversive or unpleasant) environmental condition is removed or reduced in intensity. It leads to an increase in the future probability of a given behavior. For example, if a student tantrums after the BCBA asked him/her to perform a task, and the BCBA withdraws the request because of the tantrum. In such a case, the BCBA has accidentally negatively reinforced the tantrum and unwittingly made it more likely to happen in the future.