Theories of causation

Abstract

In the definition of specific learning difficulties in the first chapter I emphasized that the delay in learning must be ‘unexplained’. It is, therefore, explicit in the definition that the cause of specific learning difficulties is presently unknown. There are few things more frustrating for a doctor to say, or for a parent to hear, than that the cause of a child’s condition is unknown. There is a natural tendency in such situations to alleviate this discomfort by guessing the cause. This is not necessarily bad, as it is by developing theories and devising experiments to test them that our knowledge advances. But the danger is that in our desire to know the cause with certainty, we may come to believe in a theory so strongly that we think of it as a fact. Theories about specific learning difficulties abound. Most are based on the assumption that there is some impairment of brain function. These theories are not mutually exclusive, since each may explain one step in the chain of events that gives rise to specific learning difficulties, as shown in Figure 3.1. Let us look at these theories one by one. These theories attempt to explain the most fundamental aspect of the condition: its primary cause. It is unlikely that a single factor can be responsible for a specific learning difficulty. Rather, it seems that a number of factors must act together. Such causation is known as ‘multifactorial’. There have been two groups of factors that have been suggested in the causation of specific learning difficulties: genetic factors and environmental factors. There is strong evidence for a genetic factor playing a role in the causation of specific learning difficulties. A number of studies have shown that children with specific learning difficulties are more likely to have a close relative with the same specific learning difficulty. No consistent pattern of inheritance has been described: sometimes it seems to be inherited from the mother, at other times from the father. For all types of such learning difficulty, boys outnumber girls by about three to one.