Editing Classical conditioning (section)

==Procedures==
[[File:Ivan_Pavlov_research_on_dog's_reflex_setup.jpg|thumb|310x310px|[[Ivan Pavlov]] research on dog's reflex setup]]

===Pavlov's research===
The best-known and most thorough early work on classical conditioning was done by [[Ivan Pavlov]], although [[Edwin Twitmyer]] published some related findings a year earlier.<ref name="Pavlov">{{cite book |vauthors=Pavlov IP |orig-year=1927 |year=1960 |title=Conditional Reflexes |location=New York |publisher=Dover Publications |url=http://psychclassics.yorku.ca/Pavlov/ |access-date=2007-05-02 |archive-date=2020-09-21 |archive-url=https://web.archive.org/web/20200921213926/http://psychclassics.yorku.ca/Pavlov// |url-status=live }} (the 1960 edition is not an unaltered republication of the 1927 translation by Oxford University Press )</ref> During his research on the [[physiology]] of [[digestion]] in dogs, Pavlov developed a procedure that enabled him to study the digestive processes of animals over long periods of time. He redirected the animals' digestive fluids outside the body, where they could be measured.

Pavlov noticed that his dogs began to [[Saliva|salivate]] in the presence of the technician who normally fed them, rather than simply salivating in the presence of food. Pavlov called the dogs' anticipatory salivation "psychic secretion". Putting these informal observations to an experimental test, Pavlov presented a stimulus (e.g. the sound of a [[metronome]]) and then gave the dog food; after a few repetitions, the dogs started to salivate in response to the stimulus. Pavlov concluded that if a particular stimulus in the dog's surroundings was present when the dog was given food then that stimulus could become associated with food and cause salivation on its own.

===Terminology===
In Pavlov's experiments the ''unconditioned stimulus (US)'' was the food because its effects did not depend on previous experience. The metronome's sound is originally a ''neutral stimulus (NS)'' because it does not elicit salivation in the dogs. After conditioning, the metronome's sound becomes the ''conditioned stimulus (CS)'' or conditional stimulus; because its effects depend on its association with food.<ref>{{cite book |first1=Douglas L. |last1=Medin |first2=Brian H. |last2=Ross |first3=Arthur B. |last3=Markmen |name-list-style=vanc |title=Cognitive Psychology |date=2009 |pages=50–53}}</ref> Likewise, the responses of the dog follow the same conditioned-versus-unconditioned arrangement. The ''conditioned response (CR)'' is the response to the conditioned stimulus, whereas the ''unconditioned response (UR)'' corresponds to the unconditioned stimulus.

Pavlov reported many basic facts about conditioning; for example, he found that learning occurred most rapidly when the interval between the CS and the appearance of the US was relatively short.<ref>{{cite book |vauthors=Brink TL |year=2008 |title=Psychology: A Student Friendly Approach |chapter-url=http://www.saylor.org/site/wp-content/uploads/2011/01/TLBrink_PSYCH06.pdf |chapter=Unit 6: Learning |pages=97–98 |access-date=2012-05-30 |archive-date=2012-04-16 |archive-url=https://web.archive.org/web/20120416041211/http://www.saylor.org/site/wp-content/uploads/2011/01/TLBrink_PSYCH06.pdf |url-status=live }}</ref>

As noted earlier, it is often thought that the conditioned response is a replica of the unconditioned response, but Pavlov noted that saliva produced by the CS differs in composition from that produced by the US. In fact, the CR may be any new response to the previously neutral CS that can be clearly linked to experience with the conditional relationship of CS and US.<ref name="Rescorla_1988"/><ref name="Bouton_2016"/> It was also thought that repeated pairings are necessary for conditioning to emerge, but many CRs can be learned with a single trial, especially in [[fear conditioning]] and [[conditioned taste aversion|taste aversion]] learning.

[[Image:delay,trace conditioning.svg|thumb|right|384px|Diagram representing forward conditioning. The time interval increases from left to right.]]

===Forward conditioning===
Learning is fastest in forward conditioning. During forward conditioning, the onset of the CS precedes the onset of the US in order to signal that the US will follow.<ref name="Chang_2004">{{cite journal |vauthors=Chang RC, Stout S, Miller RR |title=Comparing excitatory backward and forward conditioning |journal=The Quarterly Journal of Experimental Psychology. B, Comparative and Physiological Psychology |volume=57 |issue=1 |pages=1–23 |date=January 2004 |pmid=14690847 |doi=10.1080/02724990344000015|s2cid=20155918 }}</ref><ref name="Chance_2008">{{cite book |vauthors=Chance P |title=Learning and Behavior. |location=Belmont/CA |publisher=Wadsworth |year=2008 |isbn=978-0-495-09564-4}}</ref>{{rp|69}} Two common forms of forward conditioning are delay and trace conditioning.

* '''Delay conditioning''': In delay conditioning, the CS is presented and is overlapped by the presentation of the US. For example, if a person hears a buzzer for five seconds, during which time air is puffed into their eye, the person will blink. After several pairings of the buzzer and the puff, the person will blink at the sound of the buzzer alone. This is delay conditioning.
* '''Trace conditioning''': During trace conditioning, the CS and US do not overlap. Instead, the CS begins and ends before the US is presented. The stimulus-free period is called the ''trace interval'' or the ''conditioning interval''. If in the above buzzer example, the puff came a second after the sound of the buzzer stopped, that would be trace conditioning, with a trace or conditioning interval of one second.
[[File:Forward Conditioning.svg]]

===Simultaneous conditioning===
[[File:Classical Conditioning.svg|thumb|Classical conditioning procedures and effects]]

During simultaneous conditioning, the CS and US are presented and terminated at the same time. For example: If a person hears a bell and has air puffed into their eye at the same time, and repeated pairings like this led to the person blinking when they hear the bell despite the puff of air being absent, this demonstrates that simultaneous conditioning has occurred.

[[File:Simultaneous Conditioning.svg]]

===Second-order and higher-order conditioning===
{{main|Second-order conditioning}}
Second-order or higher-order conditioning follow a two-step procedure. First a neutral stimulus ("CS1") comes to signal a US through forward conditioning. Then a second neutral stimulus ("CS2") is paired with the first (CS1) and comes to yield its own conditioned response.<ref name="Chance_2008" />{{rp|66}} For example: A bell might be paired with food until the bell elicits salivation. If a light is then paired with the bell, then the light may come to elicit salivation as well. The bell is the CS1 and the food is the US. The light becomes the CS2 once it is paired with the CS1.

[[File:Second Order Conditioning.svg]]

===Backward conditioning===
Backward conditioning occurs when a CS immediately follows a US.<ref name="Chang_2004"/> Unlike the usual conditioning procedure, in which the CS precedes the US, the conditioned response given to the CS tends to be inhibitory. This presumably happens because the CS serves as a signal that the US has ended, rather than as a signal that the US is about to appear.<ref name="Chance_2008" />{{rp|71}} For example, a puff of air directed at a person's eye could be followed by the sound of a buzzer.

===Temporal conditioning===
In temporal conditioning, a US is presented at regular intervals, for instance every 10 minutes. Conditioning is said to have occurred when the CR tends to occur shortly before each US. This suggests that animals have a [[Biological rhythm|biological clock]] that can serve as a CS. This method has also been used to study timing ability in animals (see [[Animal cognition]]).

The example below shows the temporal conditioning, as US such as food to a hungry mouse is simply delivered on a regular time schedule such as every thirty seconds. After sufficient exposure the mouse will begin to salivate just before the food delivery. This then makes it temporal conditioning as it would appear that the mouse is conditioned to the passage of time.
[[File:Temporal Conditioning.svg]]

===Zero contingency procedure===
In this procedure, the CS is paired with the US, but the US also occurs at other times. If this occurs, it is predicted that the US is likely to happen in the absence of the CS. In other words, the CS does not "predict" the US. In this case, conditioning fails and the CS does not come to elicit a CR.<ref>{{cite journal |vauthors=Rescorla RA |title=Pavlovian conditioning and its proper control procedures |journal=Psychological Review |volume=74 |issue=1 |pages=71–80 |date=January 1967 |pmid=5341445 |doi=10.1037/h0024109 |url=http://www.uk.sagepub.com/upm-data/23600_Ch_1.pdf |access-date=2014-04-02 |archive-date=2014-04-07 |archive-url=https://web.archive.org/web/20140407062931/http://www.uk.sagepub.com/upm-data/23600_Ch_1.pdf |url-status=live }}</ref> This finding – that ''prediction'' rather than CS-US pairing is the key to conditioning – greatly influenced subsequent conditioning research and theory.

===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.