In 1959, a comprehensive study of Jewish American intelligence was published by B.M. Levinson in the Journal of Clinical Psychology. The subjects were “candidates for admission to the kindergarten or first grade of day (Yeshiva) schools and ranged in age from four years six months to six years seven
months.”

Below are the scores of the kids on the Wechsler Intelligence Scale for Children (WISC). Because the WISC was normed circa 1947.5 and this study was published in 1959, in the third column I adjusted the scores for norm inflation.

MONOLINGUAL KIDS

Flynn effect was adjusted for using page 241 of James Flynn’s Are We Getting Smarter? (2012). The yearly rate of increase was inferred from the gains made from 1947.5 (WISC) to 1972 (WISC-R) except in the case of Similarities where Flynn is suspected of overestimating gains (Kaufman, 2010). For this subtest, the rate from 1972 to 1989 was assumed instead.

BILINGUAL KIDS

After adjusting for the Flynn effect, the monolingual kids averaged a verbal IQ of 106 and the bilingual averaged 99, suggesting a verbal IQ of 103 for the combined sample.

For Performance IQ, the monolinguals averaged 101 and bilinguals averaged 95, for an overall average of 98.

On full-scale IQ the monolinguals averaged 104 and bilinguals averaged 98, for an overall group average of 101.

Although this study confirms the verbal > performance IQ pattern that Jewish intelligence is known for, the scores are not as high as usually reported. There are several reasons for this:

  • The original WISC excluded non-whites from their norming sample so an IQ of 100 represents the average score of just white America, not America as a whole. Their scores would have been a couple points higher using norms for the entire U.S. population.
  • Roughly half the sample was bilingual and these may have been unfairly penalized by language barriers (their lowest score was Vocabulary). They may also have been raised bilingual for religious reasons, suggesting low IQ heritage.
  • Finally, the subjects were young children. Daniel Seligman writes: “Some studies show rising verbal scores as the Jewish children pass through school but the reasons for this increase are unclear. Some scholars view it as a maturational change, that is, the group is genetically programmed to improve its already superior verbal skills with age.” (source: A Question of Intelligence by D. Seligman, pg 131)