Date of Award

Spring 5-2020

Document Type


Degree Name

Doctor of Philosophy (PhD)


Psychology and Behavioral Sciences

First Advisor

Tilman Sheets


In light of a study by Gerlach and colleagues (2018) claiming to have found four personality types (a potential subset of a larger, yet-undiscovered pool, the article clarifies), the goal of the present study was to identify the percentage of people in Johnson’s Big Five IPIP-120 and -300 data sets (N = 555,764) who fall into each type. Analyses found that over 87% of cases in both samples did not fall into any personality type. Of those who fell into a personality type in the IPIP-120 data (N = 53,243), 15.17% fell into multiple types. In the ‘typed’ sample within the IPIP-300 data (N = 17,309), the percentage was 16.57%. The Average personality type, despite the claims of Gerlach and colleagues that it represents the largest type, was the least common personality type, at 1.80% for the IPIP-120 and 1.68% for the IPIP-300. The Self-Centered personality type was the most common, at 3.60% for the IPIP-120 and 3.30% for the IPIP-300. These results suggest that the vast majority of people are not likely to fall into any one of the proposed personality types, much opposed to what was written by various media outlets and a press release by Northwestern University (where the personality study took place), and calling into question the utility of these types specifically and personality types broadly. In addition, the reliance on results from machine-learning algorithms without close theoretical scrutiny is discussed.