Surprising Facts About Firstborns

Does the data support these assumptions? Yes—and the results are striking. When we looked at our respondents’ personality results, first-borns, by a fair margin, were Thinker-Judgers. Roughly 19.5 percent more ESTJs were first-borns than we would expect to see if birth order and personality were completely uncorrelated; for INTJs, the figure is 17.5 percent.