Inhibition disorders can be observed in numerous developmental and acquired pathologies in young children. In the study carried out by Corinne Catale and Thierry Meulemans (the University of Liège’s Department of Cognitive Sciences), a new method for evaluating inhibition control, RAST (Real Animal Size Test) has been put to the test (1).

Inhibition is generally considered as one of the principal dimensions of executive functions, which group together an ensemble of processes which take part in reasoning and goal orientated behaviour. Inhibition is most often defined as the process which allows us to suppress, defer or avoid a predominant response activated beforehand. It is now accepted that the notion of inhibition has recourse to different types of mechanisms (inhibition of a non-pertinent response, verbal/semantic inhibition, resistance to pro-active interference, etc.) Certain studies show that inhibitory control is present in children at an early stage of development and that it develops throughout the whole of childhood. Thus Diamond and Taylor (1996) have shown that it is between the age of three and a half and seven that developmental progress is the greatest, with a particularly significant peak around the age of six. Developmental changes continue throughout adolescence but are less marked.

The evaluation of inhibitory processes is a priority for child neuropsychology. For a long time tests developed for adults have been applied to children, without taking into account the clinical and developmental specificities of child neuropsychology. A notorious example is the classic Stroop test, in which the name of a colour appears in a colour other than that represented by the word (the person taking the test having to give the colour a word is printed in). This test evaluates the subject’s ability to inhibit an automatic response (the reading of a word, in this case). It can easily be understood that this type of test is inapplicable for children who have not yet fully mastered the reading process. Other tests have thus been specifically developed for young children who do not read (for example the Tapping test, in which the child has to inhibit his or her propensity to imitate the gestures made by the examiner). Many other tests asking for a verbal response have also been developed according to the same principle (in this type of task the child must say the opposite of what he or she sees; for example the child must say ‘day’ when presented with a card showing the moon and some stars, or ‘girl’ when faced with the image of a boy, etc.).

From a clinical point of view, it is to be noted that delays in the development of or dysfunctions within these processes can play a part in the appearance of different cognitive or behavioural disorders, which can for example be observed in attention difficulties or in hyperactivity. For this reason the evaluation of the processes of inhibition control is fundamental for child neuropsychology; the development of reliable and objective assessment tools is thus indispensable.