Distribution of Colour-blind Men in Great Britain

Abstract

DURING the past two years the colour vision of many thousands of recruits for the Royal Navy has been tested by a modified form of the Ishihara and Stilling Tests. Thus for the first time it has become possible to compare the proportions of colour-blind men in different regions of Great Britain on a large scale. Significantly greater proportions have been found to occur in the western than in the eastern half of the country. The following table gives the percentages of defectives in nine major areas of Britain, each percentage being based on more than 6,000 cases. Each percentage has also been adjusted for the lower level of intelligence which occurs in some testing centres than in other centres, since it has been found that men of very low intelligence tend to do less well at the test.