|
|
|
|
Classical conditioning
|
| |
|
| |
Classical Conditioning (also Pavlovian or Respondent Conditioning) is a form of associative learning that was first demonstrated by Ivan Pavlov . The typical procedure for inducing classical conditioning involves presentations of a neutral stimulus along with a stimulus of some significance. The neutral stimulus could be any event that does not result in an overt behavioral response from the organism under investigation.
Discussion
Ask a question about 'Classical conditioning' Start a new discussion about 'Classical conditioning' Answer questions from other users |
Recent Posts
Encyclopedia
Classical Conditioning (also Pavlovian or Respondent Conditioning) is a form of associative learning that was first demonstrated by Ivan Pavlov . The typical procedure for inducing classical conditioning involves presentations of a neutral stimulus along with a stimulus of some significance. The neutral stimulus could be any event that does not result in an overt behavioral response from the organism under investigation. Pavlov referred to this as a Conditioned Stimulus (CS). Conversely, presentation of the significant stimulus necessarily evokes an innate, often reflexive, response. Pavlov called these the Unconditioned Stimulus (US) and Unconditioned Response (UR), respectively. If the CS and the US are repeatedly paired, eventually the two stimuli become associated and the organism begins to produce a behavioral response to the CS. Pavlov called this the Conditioned Response (CR).
Popular forms of classical conditioning that are used to study neural structures and functions that underlie learning and memory include fear conditioning, eyeblink conditioning, and the foot contraction conditioning of Hermissenda crassicornis.
History
Pavlov's experiment
The original and most famous example of classical conditioning involved the salivary conditioning of Pavlov's dogs. During his research on the physiology of digestion in dogs, Pavlov noticed that, rather than simply salivating in the presence of meat powder (an innate response to food that he called the unconditioned response), the dogs began to salivate in the presence of the lab technician who normally fed them. Pavlov called these psychic secretions. From this observation he predicted that, if a particular stimulus in the dog’s surroundings were present when the dog was presented with meat powder, then this stimulus would become associated with food and cause salivation on its own. In his initial experiment, Pavlov used bells to call the dogs to their food and, after a few repetitions, the dogs started to salivate in response to the bell. Thus, a neutral stimulus (metronome) became a conditioned stimulus (CS) as a result of consistent pairing with the unconditioned stimulus (US - meat powder in this example). Pavlov referred to this learned relationship as a conditional reflex (now called Conditioned Response).
Types
Forward conditioning
During forward conditioning the onset of the CS precedes the onset of the US. Two common forms of forward conditioning are delay and trace conditioning.
Trace conditioning
During trace conditioning the CS and US do not overlap. Instead, the CS is presented, a period of time is allowed to elapse during which no stimuli are presented, and then the US is presented. The stimulus free period is called the trace interval.
It may also be called the "conditioning interval"
Simultaneous conditioning
During simultaneous conditioning, the CS and US are presented and terminate at the same time.
Backward conditioning
Backward conditioning occurs when a conditioned stimulus immediately follows an unconditioned stimulus. Unlike traditional conditioning models, in which the conditioned stimulus precedes the unconditioned stimulus, the conditioned response tends to be inhibitory. This is because the conditioned stimulus serves as a signal that the unconditioned stimulus has ended, rather than a reliable method of predicting the future occurrence of the unconditioned stimulus.
The onset of the US precedes the onset of the CS. Rather than being a reliable predictor of an impending US (such as in Forward Conditioning), the CS actually serves as a signal that the US has ended. As a result, the CR is said to be inhibitory.
Temporal conditioning
The US is presented at regularly timed intervals, and CR acquisition is dependent upon correct timing of the interval between US presentations. The background, or context, can serve as the CS in this example.
Unpaired conditioning
The CS and US are not presented together. Usually they are presented as independent trials that are separated by a variable, or pseudo-random, interval. This procedure is used to study non-associative behavioral responses, such as sensitization.
CS-alone extinction
The CS is presented in the absence of the US. This procedure is usually done after the CR has been acquired through Forward conditioning training. Eventually, the CR frequency is reduced to pre-training levels.
Procedure variations
In addition to the simple procedures described above, some classical conditioning studies are designed to tap into more complex learning processes. Some common variations are discussed below.
Classical discrimination/reversal conditioning
In this procedure, two CSs and one US are typically used. The CSs may be the same modality (such as lights of different intensity), or they may be different modalities (such as auditory CS and visual CS). In this procedure, one of the CSs is designated CS+ and its presentation is always followed by the US. The other CS is designated CS- and its presentation is never followed by the US. After a number of trials, the organism learns to discriminate CS+ trials and CS- trials such that CRs are only observed on CS+ trials.
During Reversal Training, the CS+ and CS- are reversed and subjects learn to suppress responding to the previous CS+ and show CRs to the previous CS-.
Classical ISI discrimination conditioning
This is a discrimination procedure in fook off
Latent inhibition conditioning
In this procedure, a CS is presented several times before paired CS-US training commences. The pre-exposure of the subject to the CS before paired training slows the rate of CR acquisition relative to organisms that are not CS pre-exposed. Also see Latent inhibition for applications.
Conditioned inhibition conditioning
Three phases of conditioning are typically used:
- Phase 1:
A CS (CS+) is not paired with a US until asymptotic CR levels are reached.
- Phase 2:
CS+/US trials are continued, but interspersed with trials on which the CS+ in compound with a second CS, but not with the US (i.e., CS+/CS- trials). Typically, organisms show CRs on CS+/US trials, but suppress responding on CS+/CS- trials.
- Phase 3:
In this retention test, the previous CS- is paired with the US. If conditioned inhibition has occurred, the rate of acquisition to the previous CS- should be impaired relative to organisms that did not experience Phase 2.
Blocking
This form of classical conditioning involves two phases.
- Phase 1:
A CS (CS1) is paired with a US.
- Phase 2:
A compund CS (CS1+CS2) is paired with a US.
- Test:
A separate test for each CS (CS1 and CS2)is performed. The blocking effect is observed in a lack of conditioned response to CS2, suggesting that the first phase of training blocked the acquisition of the second CS.
Applications
Little Albert
John B. Watson, founder of behaviourism, demonstrated classical conditioning empirically through experimentation using the Little Albert experiment in which a child ("Albert") was presented with a white rat to which was later paired with a loud noise. As the trials progressed, the child began showing signs of distress at the sight of the rat and other white objects, demonstrating that conditioning had taken place. Little Albert was also trained to be frightened of furry objects, like a stuffed animal and even a white coat.
Behavioral therapies
In human psychology, implications for therapies and treatments using classical conditioning differ from operant conditioning. Therapies associated with classical conditioning are aversion therapy, flooding and systematic desensitization.
Classical conditioning is short-term, usually requiring less time with therapists and less effort from patients, unlike humanistic therapies. The therapies mentioned are designed to cause either aversive feelings toward something, or to reduce unwanted fear and aversion. Classical conditioning is based on a
Theories of classical conditioning
There are two competing theories of how classical conditioning works. The first, stimulus-response theory, suggests that an association to the unconditioned stimulus is made with the conditioned stimulus within the brain, but without involving conscious thought. The second theory stimulus-stimulus theory involves cognitive activity, in which the conditioned stimulus is associated to the concept of the unconditioned stimulus, a subtle but important distinction.
Stimulus-response theory, referred to as S-R theory, is a theoretical model of behavioral psychology that suggests humans and other animals can learn to associate a new stimulus- the conditioned stimulus (CS)- with a pre-existing stimulus - the unconditioned stimulus (US), and can think, feel or respond to the CS as if it were actually the US.
The opposing theory, put forward by cognitive behaviorists, is stimulus-stimulus theory (S-S theory). Stimulus-stimulus theory, referred to as S-S theory, is a theoretical model of classical conditioning that suggests a cognitive component is required to understand classical conditioning and that stimulus-response theory is an inadequate model. It proposes that a cognitive component is at play. S-R theory suggests that an animal can learn to associate a conditioned stimulus (CS) such as a bell, with the impending arrival of food termed the unconditioned stimulus, resulting in an observable behavior such as salivation. Stimulus-stimulus theory suggests that instead the animal salivates to the bell because it is associated with the concept of food, which is a very fine but important distinction.
To test this theory, psychologist Robert Rescorla undertook the following experiment . Rats learned to associate a loud noise as the unconditioned stimulus, and a light as the conditioned stimulus. The response of the rats was to freeze and cease movement. What would happen then if the rats were habituated to the US? S-R theory would suggest that the rats would continue to respond to the US, but if S-S theory is correct, they would be habituated to the concept of a loud sound (danger), and so would not freeze to the CS. The experimental results suggest that S-S was correct, as the rats no longer froze when exposed to the signal light. His theory still continues and is applied in everyday life.
See also
Further reading
- Dayan, P., Kakade, S., & Montague, P.R. (2000). Learning and selective attention. Nature Neuroscience 3, 1218 - 1223.
- Jami, S.A., Wright, W.G. & Glanzman, D.L. (2007). . The Journal of Neuroscience, 27, 3064-3068.
- Kirsch, I., Lynn, S.J., Vigorito, M. & Miller, R.R. (2004). The role of cognition in classical and operant conditioning. Journal of Clinical Psychology, 60, 369 - 392.
- Pavlov, I. P. (1927). : An Investigation of the Physiological Activity of the Cerebral Cortex (translated by G. V. Anrep). London: Oxford University Press.
- Rescorla, R. A., & Wagner, A. R. (1972). A theory of Pavlovian conditioning. Varitions in effectiveness of reinforcement and non-reinforcement. In A. Black & W. F. Prokasky, Jr. (eds.), Classical Conditioning II New York: Appleton-Century-Crofts.
External links
|
| |
|
|
