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Race and Ethnicity

The One Drop Rule: How Black Is "Black?"

The perception of race is subjective.

Many biracial people publicly identify themselves with only one race (for example, either black or white, but not both). President Obama raised eyebrows when he checked only one box on his 2010 Census form: "Black, African American, or Negro." Halle Berry (who is biracial), in discussing her one-quarter black daughter, Nahla, has stated, "I feel she's black. I'm black and I'm her mother, and I believe in the one-drop theory." When pressed on why Nahla, who is 75 percent white, should be considered black, she conceded that Nahla may ultimately have some choice in the matter, but added, "I think, largely, that will be based on how the world identifies her." In other words, according to Berry, regardless of how she may choose to self-identify, as long as she has "one drop" of black blood, the world will see her as black.

Is this true? Clearly, there is a good deal of idiosyncratic variation from person to person in terms of how prototypical they are of a particular race. But if you average across many people, what do observers generally view as the threshold where one race ends and the other race begins?

A team of researchers led by Arnold Ho of Harvard University recently examined this question by using a face-morphing computer program. In one study, participants were presented with faces on a computer screen. They were told that each time they pressed the "continue" button the face currently on the screen would morph slightly (in reality, 1 percent increments) into a different race. They were further instructed to keep pressing "continue" until the exact moment they felt that the person on the screen now belonged to another race.

The results were as follows: On average, faces that started out 100 percent black had to be 62.13 percent white to be labeled white; faces that started out 100 percent white had to be only 44.86 percent black to be considered black. So on the one hand, there was evidence of a clear asymmetry: blackness was perceived to start earlier and last longer than whiteness. On the other hand, 44.86 percent is a long way from Berry's one-drop notion. On average, a person could be, say, 43 percent black and still be visually perceived as white.

Interestingly, these numbers changed when the faces were morphed between Asian and white. When the faces started out Asian, they had to be only 56.50 percent White to be perceived as White. When they started out white, they had to be 46.78 percent Asian to be considered Asian. In other words, Blacks are more likely to be visually perceived as non-white than Asians are.

The legal definition of race membership has a checkered history. Although the precise figure differed from state to state, many U.S. states outlined specific fractions of blackness a person needed to possess in order to be considered legally black (and therefore ineligible for rights and privileges that were exclusive to whites). Similar rules existed for Native Americans. Nowadays, the tables have turned in some respects. Because in some cases being black or Native American can be an advantage (for example, some affirmative action policies), many are motivated to see the threshold lowered so that the category is more inclusive, not less. In other words, we see some movement in the direction back toward the one-drop rule.

Research like Ho et al.'s suggests that, regardless of the legal definitions for race membership, there are subjective, psychological definitions that people carry around with them. To the extent that society believes that Blacks, Asians, and members of every race should "look the part," the Ho et al. data may be used to help inform the legal definitions of race membership.

In my next post, I will talk about related work that my colleagues and I have done, examining individual differences in these sorts of perceptions. What sorts of beliefs lead people to favor the one-drop rule and what sorts of beliefs lead to a narrower definition of a race's boundaries?


Ho, A.K., Sidanius, J., Levin, D.T., & Banaji, M. (2011). Evidence for hypodescent and racial hierarchy in the categorization and perception of biracial individuals. Journal of Personality and Social Psychology, 100, 492-506.

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