Sex differences in general knowledge.(Statistical Data Included)

1. Introduction

General knowledge or information has been a component of a number of intelligence tests for many decades. For instance, the Stanford-Binet test asks 8-year-old children to name the days of the week, which can be considered a test of general knowledge for 8-year-olds (Terman & Merrill, 1960). The Wechsler tests contain information tests which are likewise tests of general knowledge. Factor-analytic hierarchical models of intelligence such as those proposed by Carroll (1993) and Horn (1994) include general knowledge as a component of Gc, a general second-order verbal factor.

In this paper, we are concerned with the issue of sex differences in general knowledge. There is a considerable research literature on sex differences in most of the second-order abilities and a wide measure of consensus on the conclusions. This has recently been reviewed by Kimura (1999). She concludes that there are no sex differences in verbal comprehension as measured by vocabulary size, in "visual reasoning" as measured by Raven's Matrices (some prefer to call this abstract or non-verbal reasoning), or in verbal reasoning; that females obtain higher means in perceptual speed and ideational fluency; and that males obtain higher means in spatial ability. This represents the contemporary consensus and is broadly the same as the conclusion reached by Mackintosh (1998).

Although the weight of the evidence indicates that there is a negligible sex difference in vocabulary, as Kimura concludes, there is consistent evidence that males obtain higher average scores than females on the Information subtest of the Wechsler tests. This male advantage is shown in six standardization samples of the Wechsler tests in the US and Europe in Table 1, which gives the sex differences on the verbal IQs and the Information subtests expressed as d scores (the difference between the male and females means divided by the standard deviations). Males obtain consistently higher means than females on both the verbal IQs and on the Information subtests, but it will be noted that the male advantage on the Information subtests is consistently larger than on the verbal IQs.

There are two possible explanations for this phenomenon. The first is that the Information subtests of the Wechslers are biased in favor of males in the sense that they are tests of the kinds of information that males tend to possess more than females. This implies that there are other kinds of information, which females tend to possess more than males, but this information is under-represented in the test. The second explanation is that males do have more general information or knowledge than females. Our object in this study is to attempt to discover which of these two explanations is correct. We believe that the resolution of this issue requires an analysis of the major domains of information and of sex differences in these.

2. Method

We have tackled this project in two stages. The first was designed to establish the domains and factor structure of general knowledge and the second to investigate sex differences in these. The first stage of the project has been reported in Irwing, Cammock and Lynn (2001) and is summarized here.