Most people think of discrimination as one person preventing the advance of another — for example, a hiring manager may not offer an applicant a job because of his or her skin color.

But new research suggests that discrimination can work in just the opposite way. Sometimes discrimination can be the result of helping people like yourself succeed, rather than hindering others.

“We can produce discrimination without having any intent to discriminate or any dislike for those who end up being disadvantaged by our behavior,” study author Tony Greenwald said in a news release.

Even if you’re not overtly biased against another group of people, showing favoritism toward your friends or those similar to you can have the same net effect.

For instance, a boss might offer an employee a raise or a plum project because both are members of the same gym, or because their kids go to school together. Showing favoritism for people who share something with you — those in your “ingroup,” the authors say — is just as discriminatory as not assisting someone because they are different.

“Your ‘ingroup’ involves people that you feel comfortable with, people you identify with,” Greenwald added. “We usually think first of demographic characteristics like age, race, sex, religion and ethnicity as establishing an ingroup, but there are also ingroups based on occupation, neighborhood and schools attended, among other things. Outgroups are those with whom you don't identify.”

The recent University of Washington study reviewed five decades of research on discrimination, finding that discrimination was actually more often the result of giving preferential to treatment to those in one’s ingroup than it was of harming or holding hostility toward people outside it. But most researchers have, in the past, defined discrimination as the latter, which is how most of us probably think of it.

“This is not to say that prejudice and hostility are not related to outgroup discrimination,” author Thomas Pettigrew said. “But they are not as central to most discrimination as ingroup favoritism.”

The authors added that it’s natural to think of discrimination as having to do with hostility toward another person or group — the political and religious conflicts people to go war over are living proof that the “regular” kind of discrimination does exist.

But it’s also important to remember that discrimination has this other, more positive, element, which can be just as powerful. Even if you’re not overtly biased against another group of people, showing favoritism toward your friends or those similar to you can have the same net effect.

“Hostility isn't integral to the definition of discrimination; you can treat people differently without being hostile to anyone,” Greenwald said. “But it is societally important to understand how discrimination can occur both without hostility and without any intent to discriminate.”

What the study highlights is an element of discrimination that most of us probably never think about. And if we do consider it, we will likely have to acknowledge that we discriminate by playing favorites, too. And, of course, becoming more aware of habits, even subconscious ones, is the first step to changing them.

The study is published in the journal American Psychologist.