1. The clinical findings in the examination of over 30,000 men gave a very definitely higher incidence of emotional instability in the men diagnosed mentally retarded than in those diagnosed non-retarded.2. Down-grading for instability decreased as 'M' scores advanced.3. The rate of decrease in down-grading diminished appreciably in the range of average and superior intelligence.4. The evidence suggests that the rate of incidence of psychoneurosis and other patterns of emotional instability declines as the degree of intelligence advances, although this becomes much less evident in the upper ranges of intelligence.5. Possible explanations and interpretations have been discussed.Abstract Teaser