Study co-author Richard Ryan of University of Rochester and colleagues at the University of Essex in England and the University of California, Santa Barbara, said they conducted four separate experiments in the United States and Germany, each with an average of 160 college students.
"Individuals who identify as straight but in psychological tests show a strong attraction to the same sex may be threatened by gays and lesbians because homosexuals remind them of similar tendencies within themselves," said lead author Netta Weinstein, a lecturer at the University of Essex.
Students were shown words and pictures on a computer screen and asked to put these in "gay" or "straight" categories. Before each of the 50 trials, participants were subliminally primed with either the word "me" or "others" flashed on the screen for 35 milliseconds. They were then shown the words "gay," "straight," "homosexual," and "heterosexual" as well as pictures of straight and gay couples, and the computer tracked precisely their response times.
A second experiment -- in which subjects were free to browse same-sex or opposite-sex photos -- provided an additional measure of implicit sexual attraction.
Via a series of questionnaires, participants reported on the type of parenting they experienced growing up, from authoritarian to democratic.
Finally, the researcher measured participants' level of homophobia -- both overt, as expressed in questionnaires on social policy and beliefs, and implicit, as revealed in word-completion tasks.
"In a predominately heterosexual society, 'know thyself' can be a challenge for many gay individuals. But in controlling and homophobic homes, embracing a minority sexual orientation can be terrifying," Weinstein said. "These individuals risk losing the love and approval of their parents if they admit to same sex attractions, so many people deny or repress that part of themselves."
The findings were published in Personality and Social Psychology.