Читать книгу Sociology - Anthony Giddens - Страница 82

Causation cannot be directly inferred from correlation. Correlation means the existence of a regular relationship between two sets of occurrences or variables. A variable is any dimension along which individuals or groups vary. Age, gender, ethnicity, income and social class position are among the many variables that sociologists study. It might seem, when two variables are found to be closely linked, or correlated, that one must be the cause of the other. Yet this is very often not the case. Many correlations exist without any corresponding causal relationship between the variables involved. For example, over the period since the Second World War, a strong correlation can be found between the decline in pipe-smoking and the decrease in the number of people who regularly go to the cinema. Clearly one change does not cause the other, and we would find it difficult to discover even a remote causal connection between them. There are other instances in which it is not quite so obvious that an observed correlation does not imply a causal relationship. Such correlations are traps for the unwary and easily lead to questionable or false conclusions.

In his classic work of 1897, Suicide (discussed in chapter 1), Emile Durkheim found a correlation between rates of suicide and the seasons of the year. Levels of suicide increased progressively from January to around June or July and then declined over the remainder of the year. It might be supposed that temperature or climatic change is causally related to the propensity of individuals to commit suicide. We might surmise that, as temperatures increase, people become more impulsive and hot-headed, leading to higher suicide rates. However, the causal relationship here has nothing to do directly with temperature or climate at all. In spring and summer, most people engage in a more intensive social life than they do in the winter months. Those who are isolated or unhappy tend to experience an intensification of these feelings as the activity level of other people around them rises. Hence they are likely to experience acute suicidal tendencies more in the spring and summer than they do in autumn and winter, when the pace of social activity slackens. We always have to be on our guard, both in assessing whether correlation involves causation and in deciding in which direction causal relations run.