In psychology, many of the behavioral phenomena described by this science have to do with learning.

Overshadowing is one of the concepts that refer to how we learn through classical conditioning, and in this article we’ll see what it is. Let’s start with the basics.

What is classical conditioning?

Basic psychology explains, describes and defines the laws that govern the organism, understanding it as behavior, and the processes underlying it. Within it, we find the psychology of learning and, more specifically, classical conditioning.

Classical conditioning (CC) or Pavlovian conditioning is a central theme in the psychology of learning, as well as one of its basic principles.

This type of learning involves automatic or reflex responses, not voluntary behaviour (this is different from operant or instrumental conditioning).

CC consists of the creation of a connection between a new stimulus and an already existing reflex; it would be, therefore, when 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 that normally provokes this response.

CC allows teaching children to perform desired behaviours by associating stimuli to other unconditioned stimuli that already generate in the child the target behaviour (e.g. associating a bell (EC) to the fact of starting the playground (EI), so that children get ready to go out to the playground when they hear the bell.

This type of learning will make it possible to establish routines that help children anticipate the behaviours they need to carry out. This learning is vitally important when working with children who have special educational needs, as these routines prevent them from becoming disoriented and from developing anxiety.

Shadowing: the importance of salience

From the classical conditioning we can differentiate different complex phenomena. One of them is overshadowing .

This was initially described by Ivan Pavlov in 1927, and consists of the joint presentation of two stimuli that differ in salience (saliency) followed by an unconditioned stimulus (EI).

This sequence implies a higher intensity conditioned response (CR) to the most outgoing stimulus. Thus, if A is more salient than B, it will be conditioned more quickly than B, and also will make it more difficult to condition B .

Thus, the more the EC stands out from the rest of the stimuli present during acquisition (which may be one or more), the better the conditioning.

Shading experiments

A typical shading experiment would include two groups of subjects and two stimulation elements, one high intensity (A) and one low intensity (b).

For the shading group, the two stimuli are presented together (Ab) as a composite key and paired with reinforcement during conditioning . For the control group, only the low intensity stimulus (b) is presented during conditioning.

Tests are conducted for each group presenting only the weakest element of the stimulus (b). These tests show a lower number of responses (CR’s) to b in the shadow group than in the control group.

Thus, we can see how the presence of A alters the control of the behavior by the weakest stimulus, b. In more precise terms, we will say that A has subtracted from B the power of association with the reinforcer.

But, what are the characteristics of salience? One of them would be the intensity of the stimulus, and although there are others, for research purposes we neutralize the other variables that determine salience and only vary the intensity.

Thus, by logic, of two environmental elements (neutral stimuli) paired with EI, we will pay more attention to the most outstanding, the one that calls our attention the most , and this will lead to a greater conditioned response.

An example

We can think of an example to visualize this type of procedure; the traffic signs .

A sign painted on the ground will be less prominent than a sign on a pole, and therefore less effective. In this case, the salience will also have to do with the location of the sign and our position while driving (the sign on the pole will be more visible to us, more striking).

In addition, we know that the sign on a pole has preference over one painted in the dream, in case we find a contradiction between the two.

Differences between shadowing and blocking

We should not confuse shadowing with a similar but not identical phenomenon, blocking effect.

This also consists of a classical conditioning phenomenon , and it is that a conditioned stimulus (EC1) is paired with an unconditioned stimulus (EI) in a first phase, and in a second phase both the EC1 and a new conditioned stimulus (EC2) are paired with the EI; all of this causes the learning of EC2 to be impeded.

In other words, the conditioning of a first CE (CE1) makes it difficult to learn a second CE (CE2) later on.

Thus, we see that both in the shadowing and in the blocking, one stimulus makes another lose associative power , although for different reasons (in the shadowing by the salience of the stimulus, and in the blocking by the pre-exposure of the EC1).

Bibliographic references:

  • Pérez, V., Guitérrez, M., Gracía, A., and Gómez, J.(2017). Basic psychological processes: a functional analysis. Madrid (Spain): UNED.
  • Domjan, M. (2009), Principles of Learning and Behaviour, Madrid, Spain: Thomson.