SAN ANTONIO — Some of the world’s pre-eminent experts on bias discovered an unexpected form of it at their annual meeting.

Discrimination is always high on the agenda at the Society for Personality and Social Psychology’s conference, where psychologists discuss their research on racial prejudice, homophobia, sexism, stereotype threat and unconscious bias against minorities. But the most talked-about speech at this year’s meeting, which ended Jan. 30, involved a new “outgroup.”

It was identified by Jonathan Haidt, a social psychologist at the University of Virginia who studies the intuitive foundations of morality and ideology. He polled his audience at the San Antonio Convention Center, starting by asking how many considered themselves politically liberal. A sea of hands appeared, and Dr. Haidt estimated that liberals made up 80 percent of the 1,000 psychologists in the ballroom. When he asked for centrists and libertarians, he spotted fewer than three dozen hands. And then, when he asked for conservatives, he counted a grand total of three.

“This is a statistically impossible lack of diversity,” Dr. Haidt concluded, noting polls showing that 40 percent of Americans are conservative and 20 percent are liberal. In his speech and in an interview, Dr. Haidt argued that social psychologists are a “tribal-moral community” united by “sacred values” that hinder research and damage their credibility — and blind them to the hostile climate they’ve created for non-liberals.