The most important graph in educational psychology is buried in an appendix of an article, but it explains so much about how individual differences have important consequences in adulthood. The graph comes from an article by Jonathan Wai and his colleagues (2009, p. 834) and is shown below.
The graph is based on data from Project TALENT, a study of a representative sample of about 400,000 high school students in the 1960s and which continued for 11 years after their high school graduations. The students were divided into nine groups according to the field in which they earned a college or graduate degree. These fields are arranged (from left to right) in order of the average overall IQ for degree earners in each field. They are education, business, arts, social science, humanities, biological science, math and computer science, physical science, and engineering. The overall IQ (“General Ability Level”) is listed as z-scores, which means that every 0.1-unit increment in the graph is equal to 1.5 IQ points.
Therefore, the average IQ for a person who earned an education degree was about 108. In the social sciences, it was 112. In physical sciences and engineering, the average IQ is about 119. Because most of these students self-selected into college majors, it seems that some areas of study are attracting very smart students and others . . . are not so much.
But overall IQ is not the whole story. (It rarely is in education.) The three dots connected by lines within each group indicate the pattern of broad abilities: verbal, spatial, and mathematical ability. Notice how different disciplines have different patterns of ability. Education, social sciences, and humanities tend to attract people with spatial abilities that are much lower compared to their verbal and math abilities. For math and computer science, physical science, and engineering, mathematical abilities tend to be highest and verbal abilities are lowest (though still well above the general population’s average).
Why do these fields attract people with these particular mix of abilities? Probably because that is the mix of skills used in these fields. The social sciences, education, and humanities are probably attracting people with relatively low spatial ability because these fields don’t require people to use spatial abilities. So, low spatial competence doesn’t damage anyone’s chances of earning a degree in these areas. Likewise, engineering requires high math and spatial competence, so people with that profile of abilities are attracted to the field.
This tells me that successful completion of a degree requires more than just brute smarts and an above-average IQ. It also takes a mix of verbal, spatial, and mathematical abilities that align with the abilities that are used within a field.
Finally, within each discipline, the people who earn higher degrees have higher verbal, spatial, and mathematical abilities than people who earn lower degrees. This indicates that people who earn master’s and doctorate degrees are smarter than those who stop after earning a bachelor’s degree (though the magnitude of the IQ difference is not shown on the graph).
All of this is a lot information packed into a single graph, which is why this is the most important graph in educational psychology. The graph tells psychologists so much about differences across disciplines, for example, which ones seem to require a higher overall IQ and which do not. It also shows which abilities are relatively more important in each discipline, which is vitally important for vocational counseling. (Don’t encourage someone with mediocre spatial ability to enter computer science!) Finally, within disciplines it shows the importance of high ability in earning a graduate degree and that differences among abilities become exaggerated as the education level of individuals increases.
An Aside About Education
It is hard to ignore the unimpressive performance of education degree holders. An average IQ of 108 is not low; it is a higher IQ than 70% of the population. 108 is about what the average IQ for a registered nurse, insurance adjuster, sales manager, or purchasing agent (Worderlic, Inc., 1999, p. 27). The education degree holders’ performance just looks low compared to other college degree holders.
Nevertheless, this may explain why education majors are perceived as being easier than other college majors. I think this also explains why gifted education has so little influence among teachers. Most teachers are probably not gifted themselves and will have a hard time understanding the needs of very bright children.
Wai, J., Lubinski, D., & Benbow, C. P. (2009). Spatial ability for STEM domains: Aligning over 50 years of cumulative psychological knowledge solidifies its importance. Journal of Educational Psychology, 101(4), 817-835. https://doi.org/10.1037/a0016127
Wonderlic, Inc. (1999). Wonderlic Personnel Test & Scholastic Level Exam user’s manual. Wonderlic, Inc.