"Women may respond to porn, but not in a way that counts," the Philadelphia Inquirer informed us this weekend. We were perplexed. With a subject as loaded and variable as porn, what "counts" and what doesn't? And in what ways were women's responses falling short?

Turns out this bulletin referred to a study we mentioned last month, which used thermal imaging to disprove the myth that women take longer to become aroused than men. The McGill University Health Centre study found that male and female subjects became physiologically turned on within about 30 seconds of watching pornographic videos. Female subjects reached peak arousal levels after 12 minutes of viewing, while men hit maximum after 11 minutes. (It's worth noting that the study relied on hetero porn, though researchers used videos designed by the Kinsey Institute to appeal to both genders.)

Researchers wondered why, if both sexes get revved up watching blue movies, women don't make up more of the industry's audience. Lead researcher Irv Binik postulated that physical arousal alone doesn't do the trick for most women: "In women, you get a lot of disagreement between what the body is saying and what the mind is saying," he surmised. (When it comes to porn, we can imagine women's minds might come up with all manner of commentary, from "that looks painful" to "that looks sexy" to "regardless of how this looks, I have problems with the adult entertainment industry.") Some women probably have louder inner monologues than others, but the idea that women tend to consider rational as well as hormone-driven factors when it comes to sex -- and porn -- doesn't strike us as a bad thing.

Another proposed explanation has to do with that old truism about men being biologically programmed to spread their seed -- some scientists speculate that evolution plays a part in porn's gender gap. British zoologist Robin Baker says male animals tend to watch other animals copulate and to become aroused when doing so, which "could prove advantageous if you're tough enough to force the other male off and take over, or sneaky enough to wait till he leaves and move in while the female is still in the mood," the Inquirer reports. Interesting: a biological explanation for the porntastic gang bang.

Either way, Inquirer sex writer Faye Flam summarizes that "the pornography industry owes its billions to an ancient animal instinct." Just another reminder that while human interest in porn may reflect natural drives, skin flicks aren't necessarily speaking to our most evolved selves.