Editing Operant conditioning (section)

====Two-process theory of avoidance====

This theory was originally proposed in order to explain discriminated avoidance learning, in which an organism learns to avoid an aversive stimulus by escaping from a signal for that stimulus. Two processes are involved: classical conditioning of the signal followed by operant conditioning of the escape response:

a) ''Classical conditioning of fear.'' Initially the organism experiences the pairing of a CS with an aversive US. The theory assumes that this pairing creates an association between the CS and the US through classical conditioning and, because of the aversive nature of the US, the CS comes to elicit a conditioned emotional reaction (CER) – "fear." b) ''Reinforcement of the operant response by fear-reduction.'' As a result of the first process, the CS now signals fear; this unpleasant emotional reaction serves to motivate operant responses, and responses that terminate the CS are reinforced by fear termination. The theory does not say that the organism "avoids" the US in the sense of anticipating it, but rather that the organism "escapes" an aversive internal state that is caused by the CS.
Several experimental findings seem to run counter to two-factor theory. For example, avoidance behavior often extinguishes very slowly even when the initial CS-US pairing never occurs again, so the fear response might be expected to extinguish (see [[Classical conditioning]]). Further, animals that have learned to avoid often show little evidence of fear, suggesting that escape from fear is not necessary to maintain avoidance behavior.<ref name="Pierce 2004">Pierce & Cheney (2004) Behavior Analysis and Learning</ref>