Understanding the Male-Female IQ Ratio: An Analysis of Average Annual IQ Scores

The average IQ for females, much like for males, is generally considered to be around 100, based on the standard IQ scale. The mean score on this scale is 100, with a standard deviation of 15. While this suggests that, on average, males and females have similar IQ scores, it is important to note that IQ tests can measure different types of intelligence and can be influenced by various factors, such as socio-economic status, education, and cultural background.

Assumptions and Variations Across Regions

The answer to the question what is the average annual IQ of a female? is complex and depends on numerous assumptions. For example, in a developed nation, we can usually provide a more reliable answer based on available data. However, in undeveloped nations, the answer can vary significantly.

In the United States and most European nations, data shows that males, especially past the age of 16, generally have a mean IQ that is 4–6 points higher than females. Males also display more variability, with a larger standard deviation. This means that as IQ goes into the right tail, there are significantly more males than females, and the ratio increases as you go to higher and higher levels. Research by Nyborg highlights that there are differences in the ratio of males to females across different breeding groups, with the lowest ratio being observed among Whites.

Sex Differences in Broad Abilities

There are also notable sex differences in broad cognitive abilities. The largest difference is often seen in clerical speed (Gs, as categorized by the Cattell-Horn-Carroll model), which typically favors females. In contrast, most other abilities such as math, mechanical reasoning, and spatial reasoning generally favor males, sometimes by significant margins. These differences underscore the complexity and variability of intelligence across genders.

Cognitive Science Insights: Differences in Brain Function

The neurology of intelligence has revealed that male and female brains do not operate the same way. Richard Haier, one of the pioneering researchers in this field, emphasized that male and female data should not be combined in psychometric studies due to the significant differences in brain function. These differences are evident in the specific brain regions that are active when performing specific cognitive tasks. For instance, when performing a math operation, males typically engage the parietal and frontal brain regions, while females use only the frontal region.

Other factors, such as the size and efficiency of the corpus callosum, also demonstrate sex differences. Females often show a more efficient corpus callosum compared to males, which facilitates more overall brain activity in certain tasks. Males, in contrast, show more focused activity in a relatively small area of one hemisphere. These differences contribute to a speed advantage for males, but it is important to recognize that these differences do not imply a superiority or inferiority of one gender over the other.

Theoretical and Practical Implications

Within cognitive science, there is no question that there are sex differences that impact intelligence. This is particularly true for males, who exhibit more variability in IQ scores, leading to a higher number of males in both tails of the Gaussian distribution. Although the male advantage at the mean is evident in many studies, a few have shown little difference, primarily due to the tests used and the study design.

As one moves upward in IQ, the ratio of males to females increases significantly, particularly in areas appropriate for STEM (Science, Technology, Engineering, and Mathematics). Notably, a higher male-to-female ratio is observed among Hispanics and even higher in the African American community. This underscores the importance of understanding these differences for tailored educational and professional opportunities.

For reference, the figure below illustrates the psychometric g (general intelligence) scores measured by the SAT for males and females. It is clear that males have a more pronounced advantage in general mental ability:

[Image: Males have greater g: Sex differences in general mental ability from 100,000 17- to 18-year-olds on the Scholastic Assessment Test]
Source: Males Have Greater g: Sex Differences in General Mental Ability from 100,000 17- to 18-Year-olds on the Scholastic Assessment Test, Douglas N. Jackson, J. Philippe Rushton, Intelligence, Vol. 34, 2006, pp. 479-486.

A similar difference is seen in large math scores as depicted below:

[Image: Large math sex difference]
Source: The College Entrance Examination Board, 2004.

Ultimately, understanding the male-female IQ ratio and its implications is crucial for educators, policymakers, and anyone interested in the cognitive and academic performance of different genders. These insights can help shape more inclusive and effective educational strategies.