It may have less to do with racism and more to do with the way our brains process information, Associate Prof , of the university's department of psychology, said this week.
The phenomenon of identifying with the minority group is known as hypodescent.
Mr Obama, whose mother was a white American and whose father was Kenyan, is generally regarded as black, even though he is as much white as black.
Associate Prof Halberstadt and his US colleagues, Steven J. Sherman, from Indiana University, and Jeffrey Sherman, from the University of California, carried out two studies in New Zealand.
One study asked 36 Chinese people and 46 Caucasians to quickly classify images of Chinese-Caucasian face blends in terms of their racial identity. As expected, the Caucasians more familiar with Caucasian faces were more likely to classify ambiguous faces as Chinese.
The second study created artificial majority and minority racial groups and asked 89 participants to learn them. The participants classified ambiguous faces as being members of the groups they had learned second.
Human brains processed new information as efficiently as possible, Associate Prof Halberstadt said. When a person's brain already knew something about a group, it would search for what was different about another group of people who did not look the same. The most immediately apparent difference often was skin colour.
"Through our face perception research we show that hypodescent need not be motivated by prejudice or anything else, and that the same minority-biased perception of mixed-race individuals can emerge as a simple result of how our brains learn new groups."
