Nathan Ensmenger explains why computer programming is dominated by men today:

This 1960s advertisement targeted women computer operators for replacement by upgraded technology:

In 1967, despite the optimistic tone of Cosmopolitan’s “Computer Girls” article, the programming profession was already becoming masculinized. Male computer programmers sought to increase the prestige of their field, through creating professional associations, through erecting educational requirements for programming careers, and through discouraging the hiring of women. Increasingly, computer industry ad campaigns linked women staffers to human error and inefficiency.

At the same time, new hiring tools—including tools that were seemingly objective—had the unintended result of making the programming profession harder for women to enter.  Eager to identify talented individuals to train as computer programmers, employers relied on aptitude tests to make hiring decisions. With their focus on mathematical puzzle-solving, the tests may have favored men, who were more likely to take math classes in school. More critically, the tests were widely compromised and their answers were available for study through all-male networks such as college fraternities and Elks lodges.

According to Ensmenger, a second type of test, the personality profile, was even more slanted to male applicants. Based on a series of preference questions, these tests sought to indentify job applicants who were the ideal programming “type.” According to test developers, successful programmers had most of the same personality traits as other white-collar professionals. The important distinction, however, was that programmers displayed “disinterest in people” and that they disliked “activities involving close personal interaction.” It is these personality profiles, says Ensmenger, that originated our modern stereotype of the anti-social computer geek.

Today, we continue to assume that the programmers are largely anti-social and that anti-socialness is a male trait. As long as these assumptions persist, says Ensmenger, the programming workforce will continue to be male-dominated. Although the stereotype of the anti-social programmer was created in the 1960s, it is now self-perpetuating. Employers seek to hire new recruits who fit the existing mold. Young people self-select into careers where they believe they will fit in—for example, women currently comprise 18% of computer science undergraduate majors, down from 37% in 1985.

I never realized that in the 1960's computer programmers were SELECTED FOR ANTI-SOCIALNESS.