Should such racial characterizations of people like Obama -- who have one black parent and one white parent -- really matter?

According to a new Northwestern University study, they do matter.

The findings suggest that the immediate response of non-black study participants is to categorize a racially ambiguous person as black when it was known that one of the person's parents was black and one was white.

In other words, when study participants knew of the person's black-white ancestry, in comparison to not knowing of the parentage, they quickly adhered to the simplistic characterization of biracial people as black, said Northwestern's Destiny Peery.

Social psychological research demonstrates a relationship between social categorizations and subsequent behavior. "It is possible that once multiracial individuals are categorized as black, for example, they may subsequently encounter stereotyping and prejudice consistent with this categorization," she said.

Peery, a graduate student in psychology and Galen V. Bodenhausen, professor of psychology and marketing at Northwestern, are co-investigators of "Black + White = Black: Hypodescent in Reflexive Categorization of Racially Ambiguous Faces." The article appeared in the October issue of the journal Psychological Science.

To address how black-white biracial people are commonly categorized, non-black study participants were asked to view a series of profiles of college students, with photos that depicted each one as black, white or racially ambiguous. Some of the racially ambiguous photos were accompanied with profiles indicating that one of the student's parents is black and the other is white.

Later when participants completed spontaneous or immediate racial categorization tasks, they were more likely to consider the racially ambiguous faces to be black when the person was known to have mixed-race ancestry, compared to not having that knowledge.

Upon more thoughtful reflection, however, study participants were more likely to categorize the same ambiguous faces with the known mixed-race parentage as "multiracial."

"Ironically, when judgments about the ambiguous faces were based on the first, immediate reaction, the explicit information about biracial ancestry increased black categorizations, whereas when the judgments were more deliberate, this same information increased multiracial categorizations," Peery said.

The study highlights the legacy of hypodescent in racial categorization in the U.S. According to hypodescent, a child of mixed-race ancestry is assigned to the race of what society considers the socially subordinate parent. Historically, mixed-race children in slave societies were most commonly assigned to the race of their non-Caucasian parent. In the most extreme manifestation of hypodescent in the United States, the one-drop rule holds that if a person has one drop of black blood, he or she is considered to be black.

"Progress in recognizing complex racial identities has been slow in coming," Peery noted. It was not until 2000 that people were allowed to identify with more than one race on U.S. Census forms.

Given the increased attention to multiracial people today and efforts to allow them to identify with all parts of their racial identity, many believe that hypodescent is an outdated rule in racial categorization.

"The question of how ordinary people categorize multiracial people remains a complicated and timely question," said Peery. "Our study suggests that knowledge of mixed-race ancestry may still serve, at a reflexive or automatic level, to highlight only one aspect of a multiracial person's identity -- the minority aspect."

Right or wrong, the automatic relegating of multiracial people to one racial category is very much a part of American history, Peery said.

"The good news," she says, "is that we can look to the increased awareness of a multiracial population in the U.S. as a sign of possible changes to come in racial categorization."

Source: Northwestern University