UK study claims men have higher average I.Q. than women

August 27, 2005

In a study accepted for publication by the British Journal of Psychology, Dr. Paul Irwing (Manchester Business School, Senior Lecturer in Organizational Psychology) and Prof. Richard Lynn (University of Ulster, Professor Emeritus) conclude that men are on average five points ahead on IQ tests. The study also found that men outnumbered women in increasing numbers as intelligence levels rise. There were twice as many with IQ scores of 125, a level typical for people with first-class degrees. When scores rose to 155, a level associated with genius, there were 5.5 men for every woman.

Professor Lynn has a number of previous articles arguing that there are differences in intelligence between racial groups. In a 2003 study, he found a correlation between average IQ and prosperity in 60 countries. In a letter to The Psychologist, Professor Lynn claimed “Men have larger brains than women by about 10% and larger brains confer greater brain power, so men must necessarily be on average more intelligent than women.” Most psychologists view brain size as less significant than numerous other gender differences. One reason brain size may not be significant is that the majority of the brain is not involved in "providing intelligence" but rather performs mundane tasks; such as regulating pulse and breathing, processing inputs from the five senses, and providing redundancy in case of brain damage. Larger brains may contain more space devoted to such functions, and the same or even less space devoted to intelligence. Colloquially, elephants and whales have brains many times the size of the human brain, yet do not appear to be more intelligent.

Earlier this year, the president of Harvard University, Lawrence Summers, sparked a controversy when he suggested that "intrinsic aptitude" was responsible for the low numbers of women at the top in many fields, especially in science and engineering. In response to Summers comment, Stephen Pinker and Elizabeth Spelke held a debate on the conclusions which can be drawn from the extensive existing scientific research on gender differences. Spelke held that discrimination remained the primary factor keeping women from going into physics, mathematics, and computer science; while Pinker suggested that life choices were more important today. This debate is considered an exceptionally good introduction to the subject for lay-persons.

Several subtle points popularized by the Pinker vs. Spelke debate are relevant to the Irwing & Lynn study. First, females benefit significantly from single sex education, but single sex education has little impact upon males. As a consequence, the Irwing & Lynn study can not lay claim to a biological difference in intelligence, unless it restricts itself to women attending all girls schools. Secondly, the process of natural selection leads males of any species to have more variance in most traits. As a result, Stephen Pinker suggests that one should find "more geniuses and more idiots" among human males (see Pinker slide 41). As a consequence, any omission of people at the lower end of the IQ spectrum would bias the average male IQ upward, relative to the average female IQ.

Neither Pinker nor Spelke suggests brain size is particularly important. However, both agree that men and women have different mental strengths and even handle various mental tasks differently. Both see these differences as an asset to the scientific community.

IQ tests have been criticized for testing how similar a person's thought processes are to the author of the tests, primarily men, rather than how intelligent they are. In particular, some tests have been biased towards thought processes where males are dominant, such as 3D spatial rotation and visualization. Tests devised by females would be more likely to emphasize female strengths, such as computation and communication. Many modern IQ tests attempt to control for gender differences by including more questions targeted at female strengths. However, such efforts are hampered by the lack of a clear definition of intelligence.