1. D. S. Falconer Introduction to Quantitative Genetics (Longman Essex UK ed. 3 1989) pp. 126 and 173–174.
2. The twin correlations used in the report by McClearn et al. are based on the first principal component index of general cognitive ability also discussed in the report. Results similar to those in Table 1 are obtained with the use of twin correlations from the Wechsler Adult Intelligence Scale given by McClearn et al. and from a paper by Bouchard and McGue (6).
3. S. P. Otto F. B. Christiansen M. W. Feldman Morrison Institute for Population and Resource Studies Paper No. 64 (Stanford University Stanford CA 1995).
4. Cloninger C. R., Rice J., Reich T., Am. J. Hum. Genet. 31, 176 (1979).
5. Rao D. C., Morton N. E., Lalouel J. M., Lew R., Genet. Res. Camb. 39, 187 (1982).