>From http://www.apa.org/releases/homophob.html
WASHINGTON -- Psychoanalytic theory holds that homophobia -- the fear, anxiety, anger, discomfort and aversion that some ostensibly heterosexual people hold for gay individuals -- is the result of repressed homosexual urges that the person is either unaware of or denies. A study appearing in the August 1996 issue of the Journal of Abnormal Psychology, published by the American Psychological Association (APA), provides new empirical evidence that is consistent with that theory.
Researchers at the University of Georgia conducted an experiment involving 35 homophobic men and 29 nonhomophobic men as measured by the Index of Homophobia scale. All the participants selected for the study described themselves as exclusively heterosexual both in terms of sexual arousal and experience.
Each participant was exposed to sexually explicit erotic stimuli consisting of heterosexual, male homosexual and lesbian videotapes (but not necessarily in that order). Their degree of sexual arousal was measured by penile plethysmography, which precisely measures and records male tumescence.
Men in both groups were aroused by about the same degree by the video depicting heterosexual sexual behavior and by the video showing two women engaged in sexual behavior. The only significant difference in degree of arousal between the two groups occurred when they viewed the video depicting male homosexual sex: 'The homophobic men showed a significant increase in penile circumference to the male homosexual video, but the control [nonhomophobic] men did not.'
Broken down further, the measurements showed that while 66% of the nonhomophobic group showed no significant tumescence while watching the male homosexual video, only 20% of the homophobic men showed little or no evidence of arousal. Similarly, while 24% of the nonhomophobic men showed definite tumescence while watching the homosexual video, 54% of the homophobic men did.