IQ and negative emotionality: The GSS asked respondents four questions: How many days out of the past week were you: 1) angry, 2) anxious and tense, 3) sad, and 4) fearful that something would happen to you? Answers were all intercorrelated. I converted them to z scores and summed them to create an index of negative emotionality (also called neuroticism). The alpha coefficient is .68.
Here are the mean scores for smart people (those scoring 9 or 10 on the vocabulary quiz) and for everyone else:
Mean negative emotionality (N = 935)
Smart group .62
Everyone else -.11
The difference between the two groups is significant at the 95% confidence level. The gap is 26% of one standard deviation which indicates a small difference.
The results seem right, but I am not sure why smart people are more neurotic. Perhaps a reader steeped in the science has an idea.
It does seem like there is a calmness that comes with not thinking about things much.