Some people are relatively good at this Stroop task. They are able to inhibit the automatic reading response and ignore the word, performing the task quickly and with very few errors. Others have difficulty with the task and may make errors or do it very slowly. These differences between people may indicate different capabilities in terms of inhibitory control. Just as people differ in their memory abilities, people differ in their inhibitory control. For each individual, inhibitory control may change during the day, for example if we are tired or have drunk alcohol. These changes in inhibitory control will be reflected in our performance on the Stroop task.

Being able to assess an individual’s inhibitory control is important, particularly if they have extreme problems in this area. Neuropsychologists study inhibitory control and how it is affected by brain damage, because problems with inhibitory control are common complaints after a head injury.

Children have more difficulty with the Stroop task than adults. This is not because they are abnormal but because their capacity to inhibit has not reached full maturity. By the time children reach mid-adolescence, their ability is almost fully mature and they perform inhibitory control tasks at a similar level to adults. When attempting to measure inhibitory control in young children, there are some difficulties. Take for example, the Stroop task. Because reading is not well established or fluent in children, we cannot assume that reading is automatic. In children under 6 years of age, we cannot use the Stroop task at all because these children can rarely read the words. In this case, children would perform relatively well on the Stroop task. However, this would not be because they were able to inhibit word reading very well, but because they experience no interference as they were not faced with automatic word reading.

In order to assess inhibitory control in children, we need to look at the kinds of task that children do perform automatically. The animal-stroop task is one task that has been developed specifically for use with children. This task assumes that a child can easily name pictures of animals, such as:

"duck"	"sheep"

Most children over the age of three or so have little difficulty in naming these animals very quickly. In fact, young children will name these pictures without any prompting, i.e. “automatically”.

In the animal-stroop task, we ask children to look at pictures where the head of the animal has been swapped with another animal. In this case, we ask the child to give us the name for the “body” of the animal. Because the face of the animal pictures is so prominent, children find it difficult to ignore. Therefore, just as with the coloured word version of the Stroop task, children have to inhibit the response based on the face in order to correctly name the body of the animal.

Research conducted using this task has found that children experience the same pattern of difficulties with the animal-stroop task that adults have with the coloured word Stroop task.

To find out more about inhibitory control, you can read an extract from the Open University's Child Development course (ED209),  executive functions in childhood.