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Null Sex Differences in General Intelligence: Evidence from the WAIS-III

  • Roberto Colom (a1), Luis F. García (a1), Manuel Juan-Espinosa (a1) and Francisco J. Abad (a1)


There is an increasing number of studies claiming that the sex differences in general intelligence are “real.” The empirical evidence is based on the summation of the standardized sex differences in several cognitive batteries. However, the scientific construct of general ability rests on the correlations among test scores, rather than on their summation. The latter (ability in general) is an arbitrary variable, not a scientific construct. General ability is not a function of any particular cognitive test, but a source of variance evidenced by the correlation between several diverse tests, each of which reflects general ability (g) to some extent, but also group factors and test specificity. Because there are important educational, economic, and social consequences of a group difference in general ability, it is especially germane to evaluate the possibility of an average sex difference in its proxy measures, such as IQ. The Spanish standardization of the WAIS-III is analyzed in the present study. The sample was made up of 703 females and 666 males, aged 15-94, drawn as a representative sample of the population in terms of educational level and geographical location. Although a male advantage of 3.6 IQ points is observed, the difference is in “ability in general,” not in “general ability” (g). Given that the main ingredient of the strong association between IQ and a broad range of social correlates is g, and given that there is no sex difference in g, then the average IQ sex-difference favoring males must be attributed to specific group factors and test specificity.

Un número creciente de estudios sostiene que “existen” diferencias entre los sexos en inteligencia general. Las pruebas empíricas se basan en la suma de las diferencias estandarizadas entre los sexos en diversas baterías cognitivas. Sin embargo, el constructo científico de inteligencia general se basa en la correlación entre las puntuaciones obtenidas en los tests, no en su suma. La suma de puntuaciones (inteligencia en general) constituye una variable arbitraria, no un constructo científico. La inteligencia general no es función de un determinado test, sino que constituye una fuente de varianza puesta de manifiesto por la correlación entre diversos tests, cada uno de los cuales refleja inteligencia general (g), factores de grupo y especificidad del propio test. Puesto que existen importantes consecuencias educativas, económicas y sociales de las diferencias de grupo en inteligencia general, resulta especialmente pertinente valorar la posibilidad de que exista una diferencia promedio entre sexos en medidas como el CI. En este estudio se emplea la adaptación española del WAIS-III. La muestra está formada por 703 mujeres y 666 varones de entre 15 y 94 años de edad, representativa de la población en nivel educativo y localización geográfica. Aunque se observa una ventaja promedio de los varones de 3.6 puntos de CI, la diferencia se debe a la “inteligencia en general”, no a la “inteligencia general” (g). Dado que el principal ingrediente de la fuerte asociación que existe entre el CI y un amplio conjunto de correlatos sociales es g, y que no existe una diferencia según el sexo en g, entonces la diferencia promedio de CI que favorece a los varones debe atribuirse a los factores de grupo y a la especificidad de los tests.


Corresponding author

Correspondence concerning this article should be addressed to Roberto Colom, Facultad de Psicología.Universiad Autónoma de Madrid. Ciudad Universitaria de Cantoblanco. 28049 Madrid (Spain). E-mail:


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Null Sex Differences in General Intelligence: Evidence from the WAIS-III

  • Roberto Colom (a1), Luis F. García (a1), Manuel Juan-Espinosa (a1) and Francisco J. Abad (a1)


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