Heterosexuality, homosexuality, and erotic age preference
Heterosexual and homosexual males who erotically preferred physically mature partners were compared with respect to the erotic impact of the nonpreferred age groups (of the preferred gender) and the nonpreferred gender. Erotic impact was assessed by phallometric test of erotic gender and age preferences. This measures penile volume changes during the presentation of potentially erotic stimuli.
Homosexual males who preferred physically mature partners responded no more to male children than heterosexual males who preferred physically mature partners responded to female children. Although heterosexual males showed a (slight) erotic aversion to the male stimuli, and homosexual males did not show an aversion to the female stimuli, this difference was minimal.
source: K. Freund, R. Watson, D. Rienzo: Heterosexuality, homosexuality, and erotic age preference. Journal of Sex Research 26:1, pp. 107-117; February 1989