Since the development of psychological assessments of ‘intelligence’ at about the beginning of this century, many groups of people have been tested. By and large, most have performed at lower levels than people of north-western European origin or ancestry, who belong to the culture within which the tests were devised.

Among the poor performers, with average IQ’s of 80 to 92, have been people of southern and eastern Europe and Caucasian people from further east (Greeks, Yugoslavs, Iranians, Iraqis, Turks, Indians), tested in their homelands, mostly in large numbers and by compatriots, on ‘standard’ non-verbal or translated tests.

These relatively poor performances demonstrate the extent of cultural learning of a particular type involved in most cognitive tests. Presumably, north-western European cultural learning is required for good performances on tests coming from this cultural background, so that children from different backgrounds, even those from other areas of Europe, are likely to be disadvantaged.

Children from more widely different backgrounds, such as those from hunting and gathering groups, can be expected to be disadvantaged even further.

Nevertheless, hunting and gathering people have been tested on Western-type tests, and poor performances interpreted as indicating inferior ability. Kalahari ‘bushmen’ people in the 1930s were assigned a mean mental age of 7.5 by Porteus as a result of their performance on his Maze Test.

In the same period, Aboriginal people of north-west Australia performed poorly on this test, with ages ranging from 8.22 years to 12.17 years for adults. Aboriginal people have performed poorly, but not invariably so, on other tests.