Pavlov’s theory of stimulus substitution

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

This theory maintains that after producing classical conditioning, the effects produced by the conditioned stimulus (EC) on the nervous system are effects similar to those of the unconditioned stimulus (IE). Let’s see in detail what this theory consists of.

    classic packaging

    Recall that classical conditioning, also called Pavlovian conditioning, reactive conditioning, stimulus-response model or association learning (EE), is 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 it thanks to the associative connection of this stimulus with the stimulus which normally causes this response.

    Theory of stimulus substitution: characteristics

    The theory of stimulus substitution was proposed by Ivan Pavlov, Russian physiologist and psychologist. The theory asserts that then classical conditioning, the effects produced by the conditioned stimulus (EC) on the nervous system are similar to those of the unconditioned stimulus (EI).

    In other words, the theory holds that the triggering ability of EI is transferred to CE, hence the emergence of the conditioned response (CR). CE activates the same neural circuits that activated EI.

    Thus, the theory of stimulus substitution is based on the close resemblance that is often observed between CR and the unconditioned response (IR). As we have seen, the association between the conditioned stimulus (EC) and the unconditioned stimulus (EI) would produce a transfer of solicitation capacity from IE to ECSo it would elicit, on a conditioned level, the same mirrored reaction as IS (Jenkins and Moore, 1973).

      How it works?

      The theory of stimulus substitution suggests that when two brain centers are activated, these are connected from the experience gained.

      But why does a conditioned response (CR) occur? Let’s look at an example to understand this:

      If for example, it is associated:

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

      Light (EC) activates the “light” center of our brain. As this center is attached to the food center (from the experience acquired during repeated presentations of EN -> EI), the latter will also be activated. This way, the center of the light with the center of the food, will activate the salivary gland and produce salivation (RC).

      Thus, according to the stimulus substitution theory, the conditioned stimulus (EC) becomes a substitute for the unconditioned stimulus (EI), behaving the animal in front of the EC as if it were the EI itself.


        However, the temporary contiguity between EC and IS does not always guarantee acquisition of the conditioned response (CR), as Pavlov argued. Sometimes it happens that RC 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 stimuli.

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

        Other related theories

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

        1. Anticipation theory

        Suggested by Konorski, this author differentiated between preparatory responses and consumer responses. The CR would act as an adaptive response serving as preparation for the IS predictions.

        2. Mackintosh theory

        He argues that pre-exposure to a stimulus prevents its subsequent conditioning of CR. Mackintosh suggested that the animals try to obtain information from the environment that allows them predict the occurrence of biologically relevant events (EI).

        3. Theory of Rescorla and Wagner

        The main idea of ​​this theory is that of the competition between different stimuli to associate with the IS. In addition, the authors introduce the concept of surprise or “unexpected” from ISIS. Thus, the unconditioned stimulus gives an associative force to the EC based on the surprise.

        Bibliographical references:

        • Pavlov, IP (1927). Conditioned reflexes: an investigation of the physiological activity of the cerebral cortex. Translated and edited by GV Anrep. London: Oxford University Press. p. 142.
        • Todes, D. (1997). Pavlov Isis physiological plant. 88, 205-246.
        • Graña, J. and Carrobles, JA (1991). Classic conditioning in the addiction. Psychothema, 3 (1), 87-96.
        • Jenkins, HM and Moore, BR (1973). The form of automatic response with food or water reinforcements. Journal of Experimental Behavior Analysis, 20, 163-181.

        Leave a Comment