Some comments on my post More Census Gleanings may have got lost in the site changeover. Please repost any comments and questions and I will try to reply.
One of my replies that got lost was about the IQ of ‘Blacks’ in Britain. My post said that the Black-White differential was less than in the US, but this was questioned.
First, it should go without saying that there is no such thing as the IQ of a population. There is just the average score of a population on particular tests. The results of particular tests tend to correlate together, but a difference of 5 points or so in the population mean on different tests would not be unusual.
In my comments on the Black-White differential in Britain I was relying mainly on the following:
[1] Nicholas Mackintosh, IQ and Human Intelligence, OUP, 1998
[2] A. West, C. Mascie-Taylor, and N. Mackintosh, Cognitive and educational attainment in different ethnic groups, J. Biosocial Science, 1992, 24, 539-554
[3] N Mackintosh and C. Mascie-Taylor, The IQ question (1986), appendix to an official report on ethnic minority education in Britain.
The gist of the various studies, summarised in [1], is that early studies (1960s and early 70s) on Blacks in Britain tended to show average IQ around 85 (with Whites around 100): a similar differential to the US. However, the samples included very recent immigrants, and when these were stripped out, the gap was narrower. More recent studies (1980s onward) have shown a further narrowing of the gap. Notably, the Child Health and Education Study (1980) shows a difference of only about 5 points on non-verbal tests and 9 points on verbal tests.
There is a potential pitfall in making comparisons over time if the meaning of ‘Black’ is changing. Most obviously, there has been a large increase in the proportion of mixed-race children. However, this pitfall appears to be avoided in reference [2], where children with parents from different ethnic groups were excluded from the study. In this study West Indian (Black Caribbean) children aged 7 to 15 had mean scores between .24 and .77 standard deviations below the White British control group, varying according to age group, the average over all age groups being about .5 s.d., equivalent to about 8 IQ points.
If anyone knows of a reputable recent study that shows a differential of more than 10 IQ points (about 2/3 of a standard deviation), I would be interested to know. Also, do American readers know of any data on Black Caribbean immigrants to the US? They have the reputation of doing better, both educationally and economically, than American blacks, but I don’t know of any IQ data.
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