Intelligence and marriage satisfaction A recent letter by a Princeton alumni stated:


  Men regularly marry women who are younger, less intelligent, less
  educated. It’s amazing how forgiving men can be about a woman’s lack
  of erudition, if she is exceptionally pretty. Smart women can’t
  (shouldn’t) marry men who aren’t at least their intellectual equal.


This letter has generated a lot of controversy. But I thought it would be interesting to clarify what the scientific literature says about a few of the implicit empirical claims made in the letter.

My broad questions is: What is the relationship between intelligence of marriage partners and marriage satisfaction?

However, given the dyadic nature of the phenomena, this question can be broken down in various ways:


Is the degree to which a husband is more intelligent than a wife correlated with marital satisfaction of the wife?
Is the effect of partner intelligence on  marriage satisfaction more about similarity to one's own intelligence or is it the case that the relationship between partner intelligence and marriage satisfaction is linear and positive regardless of one's own intelligence?
Does any observed effect of partner intelligence on marriage satisfaction vary based on whether you are comparing husbands to wives or wives to husbands?
To what extent are any effects of intelligence explained in terms of other correlated outcomes (e.g., income, socio-economic status, shared values, similar educational experience, etc.)?
What are the theorised mechanisms behind any observed effects?


I'd be particularly interested in any review articles or large sample studies that have measured intelligence and marital satisfaction on both husbands and wives.
Is husband and wife intelligence corelated?

By way of background, Mascie-Taylor (1989) report IQ correlations between husbands and wives in two british samples to be r=.40 and r =.37 respectively. I had a little difficulty discerning the sample size as it's not reported in the 1989 paper. But from another paper I got the sense that each sample might have been in the 100-200 range.

Dufoul et al (2000) measured a range of cognitive measures in 318 couples. The correlation in total cognitive score between husbands and wives was r=0.36.

In reviewing the literature Dufol et al writes


  There is a wide but relatively dated literature on concordance for
  cognitive abilities among couples, which was reviewed by Vanderberg
  and Jensen [in the 70s]. Studies have shown that
  spouses were more similar in terms of global intelligence scores than
  in terms of specific cognitive performances. Indeed, intra-couple
  correlations were of the order of 0.45 for the global intelligence
  scores, as compared with 0.10 to 0.20 for the specific cognitive
  performance scores (Jensen, 1978; Vandenberg, 1972)


Thus, at a basic level it appears that there is a modest correlation between intelligence of husbands and wives. This is thus evidence of assortative matching. The causes of such a correlation are much more complicated. First, there are the many correlates of intelligence which might be an alternative basis for selection (e.g., income, education, values, socio-economic background, etc.). Second, even if intelligence was a directly relevant feature to partner selection, spousal similarity could emerge from multiple mechanisms: (a) economic exchange whereby more (or less) of the trait is sought and those with more to offer are better able to secure more from the partner; (b) explicit valuing of similarity to self. In the case of intelligence, presumably arguments for both mechanisms (and possibly others) could be made to explain the real but modest correlations in spousal intelligence, correlations which would presumably be much lower once other correlates are controlled for.

Nonetheless, this all suggests that intelligence may be relevant to marital satisfaction given that people presumably choose partners who they think will make them happy.

Correlation between intelligence and marital satisfaction

Lewak et al (1985) report the results from 81 couples. They measured intelligence using the WAIS and marriage satisfaction using the Locke-Walace Marital Adjustment Scale.

This is my attempt to represent the relevant correlations taking full scale IQ and marriage satisfaction (MS).

            Male IQ  Female IQ  Male MS  Female MS
Female IQ    0.35      
Male MS      0.06    0.14    
Female MS    0.05    0.13    
Male IQ 
 minus 
 Female IQ                       0.05    0.10
Quadratic of 
 Male minus 
 Female IQ                      -0.08   -0.03


In summary, none of the correlations between marital satisfaction and spouse IQ were statistically significant. There was a slight trend for females and males to have higher marital satisfaction if the female was more intelligent. All the correlations between discrepancies in intelligence (either signed difference operationalised as the degree to which the male was more intelligent than the female) or unsigned difference (operationalised as the squared difference in IQ between males and females) were close to zero.

Thus, on the face of it, this study suggests at least within already married couples, such variation in partner intelligence is somewhat unrelated to marital satisfaction, although interestingly there was a slight trend in the data suggesting that intelligence in females was related to both male and female marriage satisfaction.

Nonetheless, a few words of caution are in order. First, this is a small sample. I'd really like to see some larger sample studies. Second, it may be the case that factors influence marital choice, but then once choice has been made they may be less relevant to the ongoing satisfaction.

References


Dufouil, C., &amp; Alpérovitch, A. (2000). Couple similarities for cognitive functions and psychological health. Journal of Clinical Epidemiology, 53(6), 589-593.
Jensen AR. Genetic and behavioral effects of nonrandom mating. In:
Osbourne RT, Noble CE, Wey N, editors. Human variation: Biopsychology of Age, Race and Sex. New York: Academic Press, 1978. pp.
51–105.
Lewak, R. W., Wakefield Jr, J. A., &amp; Briggs, P. F. (1985). Intelligence and personality in mate choice and marital satisfaction. Personality and Individual Differences, 6(4), 471-477.
Mascie-Taylor, C. G. N. (1989). Spouse similarity for IQ and personality and convergence. Behavior Genetics, 19(2), 223-227.
Vandenberg SG. Assortative mating, or who marries whom? Behav
Gen 1972;2:127–57.