Editing Classical conditioning (section)

===Extinction===
{{main|Extinction (psychology)}}
In the extinction procedure, the CS is presented repeatedly in the absence of a US. This is done after a CS has been conditioned by one of the methods above. When this is done, the CR frequency eventually returns to pre-training levels. However, extinction does not eliminate the effects of the prior conditioning. This is demonstrated by [[spontaneous recovery]] – when there is a sudden appearance of the (CR) after extinction occurs – and other related phenomena (see "Recovery from extinction" below). These phenomena can be explained by postulating accumulation of inhibition when a weak stimulus is presented.