In terms of the first part of the paper, Humburg found that:
all three measures of cognitive skills as well as extraversion, conscientiousness, and openness to experience increase the probability of going to university... Cognitive skills seem to be the primary driver of educational attainment. For example, a one standard deviation increase in math ability is associated with an increase in the probability of entering a university of 7.7 percentage points. These effects are very large, given that only around 15% of individuals in our sample go to university. Of the personality traits that influence individuals’ probability of going to university, conscientiousness has the largest effect. A one standard deviation increase in conscientiousness is associated with an increase in probability of entering university of 1.9 percentage points. While much smaller than the impact of cognitive skills, this effect is substantial and amounts to a relative increase of the probability of entering university of 12%.
So, university students (in the Netherlands) are more conscientious and open to experience that non-university-students, and have greater verbal, maths, and information processing abilities. No surprises there. I note that the extraversion result is only marginally significant (and negative - university students are less extraverted than non-university-students).
In terms of the second part of the paper, here is the key table that summarises the results:
Extraverted students are more likely to choose to study law, or business and economics, and avoid science, technology, engineering and mathematics (STEM). Agreeable students are more likely to study social sciences (excluding business and economics). Conscientious students are more likely to study medical studies (probably due to the entry requirements that keep out low-performers) and less likely to study social sciences (that probably confirms some people's priors). Emotionally stable (least neurotic) students are more likely to study STEM and less likely to study the humanities (more on that in a moment). Finally, students who are most open to new experiences are more likely to study law and less likely to study social sciences (which the author finds surprising - so do I!). The results for gender are unsurprising too, with women more likely to study social sciences, and least likely to study STEM or business and economics.
Importantly, the effects of the personality traits on field of study choice are similar in size to the effects of the cognitive skills (whereas university vs. not-university was mostly related to cognitive skills). The results are fairly robust to the inclusion of additional control variables (parental education, income, father's occupation, migrant status). You might worry about selection bias (since only the field of study choices of students who actually went to university are observed), but I doubt that is a big factor.
On that emotional stability and humanities result, Humburg concludes:
Another explanation can be derived from Tokar, Fischer, and Subich’s (1998) finding that emotionally instable (sic) individuals exhibit higher career indecision. It may therefore be the case that less emotionally stable individuals are more likely to choose the Humanities as they have a weaker link to particular occupations than STEM and Law programmes, which enables these young people to postpone their final career decision.I'd be interested as to whether our conjoint degree students (who often seem to be studying joint degrees because they couldn't settle on one or the other) have similar personality traits. It would also be good to know, for those students who are non-conforming (in terms of their personality traits compared with others in their field of study), how well they performed academically (and in terms of getting a job, etc.). That additional work would certainly provide some valuable data for careers advisors, which is sorely lacking.