1. As Detterman (1987) has pointed out, it is a curiosity that while the study of has a long history and has contributed to an understanding of intelligence in general, there have been few explanations in terms of contemporary theories.

2. In 1969, a famous article by Arthur Jensen provided a spark that re-lit the –IQ debate. He commented that a much-lauded programme of early academic intervention for socially disadvantaged children, known as the Headstart Program, had not resulted in any increase in IQ, and that this was likely to be due to the genetic contribution to intelligence.

3.Research conducted as part of the Carolina Abecedarian Project suggests that even when significant environmental factors contribute to intellectual impairment (perhaps through lack of opportunity for learning), structured intervention does not lead to general improvements in IQ.

4. Meta-analyses suggest that the correlation between IQ and is about -0.5.

5. performance correlates with school grades at about 0.50, total years of education about 0.55 and supervisor ratings of job performance between 0.30 and 0.50. This means that performance is one of the best predictors we have of academic and work-related performance (Schmidt & Hunter, 1998).