I've been curious about and fascinated by the "sperm competition cue" portion of male sexual arousal since I first learned about it. Straight men seem to intuitively deny it. "Of course dicks don't turn me on! That's disgusting!"

And the thing is, "sperm competition" is different enough from other cues that they probably believe they are telling the truth. Visual and tactile cues provide men (gay and straight alike) direct sexual pleasure. If we look at or touch a person we feel attracted to, we experience not just sexual arousal, but sexual pleasure.

Researchers say the sperm competition cue is different. In the presence of another erect penis, men tend to become more erect and to ejaculate more and with more force. But there's a catch: it seems to all be unconscious. Straight men report not feeling sexual pleasure from the sight of the penis (or penises) even as they are becoming more aroused and erect.

Researchers believe this lack of direct sexual pleasure experience is real (and not just misreporting due to homophobia) for several reasons including how they design their studies, but one reason stands out: these same men do not become erect at JUST the sight of an erect penis. That penis has to be attached to a man having sex with a woman they can see.

No woman, no arousal.

Show them a video of a woman they're attracted to then add in a man with an erect penis, and their arousal goes up markedly.

Ask them if they find that penis sexually simulating or sexually attractive and they will say no, probably because they're not used to arousal being unrelated to sexually stimulating sight or touch, or divorced from direct sexual pleasure.

Just an example of how complex human sexuality is, made more complex by the fact that everything I just typed applies to populations of straight men on average but may vary considerably in smaller percentages of individual men.