Pavlov’s theory of stimulus substitution

This theory developed by Ivan Pavlov proposes an explanation of classical conditioning.

There are different theories that try to explain the concepts of classical conditioning. In this article we will discuss the theory of stimulus substitution, proposed by Ivan Pavlov..

This theory holds that after classical conditioning, the effects produced by the conditioned stimulus (CS) in the nervous system are similar to those of the unconditioned stimulus (UCS). Let's see in detail what this theory consists of.

Classical conditioning

Let us recall that classical conditioning, also called Pavlovian conditioning, responsive conditioning, stimulus-response model or learning by associations (E-E), is a type of associative learning. a type of associative learning which was first demonstrated by Ivan Pavlov.

It is a type of learning according to which an originally neutral stimulus (which does not provoke a response), comes to provoke a response thanks to the associative connection of this stimulus with the stimulus that normally provokes such a response.

Stimulus substitution theory: characteristics

The stimulus substitution theory was proposed by Ivan Pavlov, a Russian physiologist and psychologist. The theory states that after classical conditioning, the effects produced by the conditioned stimulus (CS) on the nervous system are similar to those of the unconditioned stimulus (UCS)..

In other words, the theory holds that the elicitor capacity of the EI is transferred to the CS, hence the appearance of the conditioned response (CR). The CE activates the same neural circuits that activated the EI.

Thus, the stimulus substitution theory is based on the close resemblance often observed between the CR and the unconditioned response (IR). As we have seen, the association between the conditioned stimulus (CS) and the unconditioned stimulus (CS) would result in a transfer of the eliciting capacity of the CS to the CS. a transfer of the eliciting capacity of the EI to the CS, so that the latter would elicit, in the same way as the EI.so that the latter would provoke, at the conditioned level, the same reflex reaction as the EI (Jenkins and Moore, 1973).

How does it work?

Stimulus substitution theory suggests that when two centers of the brain are activated, they are connected from the obtained experience.

But why does the conditioned response (CR) occur? Let's look at an example to understand it:

If for example, you associate:

• Light (EN) -> Food (EI) -> Salivation (RI)
• Light (EC) -> Salivation (RC)

Light (EC) activates the "light" center of our brain. As this center is linked to the food center (from previous experience gained through repeated presentations of EN -> EI ), the latter will also be activated. Thus, the light center linked to the food center will activate the salivary gland and produce salivation (CR)..

Thus, according to the stimulus substitution theory, the conditioned stimulus (CS) becomes a substitute for the unconditioned stimulus (UI), the animal behaving before the CS as if it were the UI itself.

Limitations

However, the temporal contiguity between the EC and the EI does not always guarantee the acquisition of the conditioned response (CR), as advocated by Pavlov. Sometimes it happens that CR occurs even when there is no strict temporal relationship between the stimuli; at other times, even CR does not occur despite the temporal contiguity between the stimuli.

In fact, experimental results carried out in relation to the theory of stimulus substitution show that conditioning with a pharmacological EI sometimes elicits a CR opposite to the IR.. This is a criticism of this theory.

Other related theories

In addition to stimulus substitution theory, there are other theories that attempt to explain classical conditioning. The most important are three:

1. anticipation theory.

Proposed by Konorski, this author differentiated between preparatory and consummatory responses.. The CR would act as an adaptive response that serves as a preparation before the anticipation of the IE.

2. Mackintosh's theory

He argues that pre-exposure to a stimulus hinders its subsequent CR conditioning. Mackintosh suggested that animals try to get information in the environment that will allow them to to predict the occurrence of biologically relevant events (BI's). (EI's).

3. Rescorla and Wagner's theory

The main idea of this theory is that of the competition among various stimuli to be associated with the EI.. In addition, the authors introduce the concept of the surprise or "unexpectedness" of the EI. Thus, the unconditioned stimulus gives an associative strength to the CE as a function of surprisingness.

Bibliographical references:

• Pavlov, I. P. (1927). Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex. Translated and Edited by G. V. Anrep. London: Oxford University Press. p. 142.
• Todes, D. (1997). Pavlov's physiological factory Isis. 88, 205-246.
• Graña, J. and Carrobles, J.A. (1991). Condicionamiento clásico en la adicción. Psicothema, 3(1), 87-96.
• Jenkins, H. M. y Moore, B. R. (1973). The form of the autoshaped response with food or water reinforcers. Journal of the Experimental Analysis of Behavior, 20, 163-181.