Read: How a focus on rich educated people skews brain studies

A decade later, however, many psychologists say that little has changed. In the process, they are raising questions about how psychology researchers should account for nationality, class, gender, sexuality, race, and other identities in their work—and expressing frustration at the lack of concrete reform.

“It’s the issue that we all like to talk about,” says the University of Kentucky psychologist Will Gervais, “but nobody likes to actually change.”

Beginning in the early 20th century, psychology researchers—who, in the field’s first decades, had often experimented on themselves—began to seek larger samples. In many cases, they turned to the most convenient captive populations they had at hand: local schoolchildren or undergraduates at their own universities. Given that recruiting people to participate in studies can be both difficult and costly, such close-to-home recruiting has persisted to the present day, though it is now sometimes augmented by services like Mechanical Turk, or MTurk, an Amazon platform that connects freelance workers (read: subjects) with low-wage, menial tasks.

Whatever the source, these samples, at least on university campuses, typically skew toward white and affluent populations. They also draw heavily from industrialized Western societies. And yet, researchers often downplay the social identities of their subjects in published research—a tactic that serves to highlight the universality of their results. “It became customary to emphasize the experimental identity of human data sources at the expense of their ordinary personal and social identity,” writes the historian Kurt Danziger in “Constructing the Subject,” a classic 1990 study.

Researchers had some good reasons to be hesitant about emphasizing identities like race or nationality. There’s a long history of scientists seeking to bolster racist, xenophobic arguments by positing, without any actual evidence, deep-seated differences among groups. Especially after World War II, intellectual currents swung in the opposite direction, emphasizing the universality of human experience.

And often those other identities don’t particularly matter. “A lot of what we do is consistent across people,” says Daniel Simons, a psychologist at the University of Illinois who has written about generalization in psychology.

Early psychology research, Simons points out, often focused on basic behaviors that were unlikely to be influenced by culture or environment. Over time, research began to study more complex, social behaviors, and “continued to assume that it was the same sort of universal principles.” Today, a lot of psychological research does examine topics where culture or particular experiences might shape or inform results—indeed, culture and environment might be at the very center of the issue. And on a lot of questions, Simons says, “we just don’t know.”