Incidentally, this could explain why it becomes painful for a man to continue thrusting after ejaculating, since that would risk scooping out his own semen as well. But there is one more factor that could be key: A scientist, though, would phrase the same question in an almost comically obscure way: As an evolutionary researcher, all this talk of how long sex lasts make me wonder: How does masturbation fit into the picture? The average time for each couple that is, averaged across all the times they had sex ranged from 33 seconds to 44 minutes. What is the mean intravaginal ejaculation latency time? Well, there are two main problems with this. The best study we have estimating the average time to ejaculation in the general population involved couples from around the world timing themselves having sex over a four-week period — using a stopwatch. Read now Julia Velten, Ph. In , researchers showed — using artificial vaginas, artificial penises, and artificial sperm corn syrup — that the ridge around the head of the penis actually scoops out pre-existing syrup from the vagina. The average median, technically across all couples, though, was 5. Why we last so long is a pretty complicated question with no clear answer, but a clue may be in the way the penis is shaped. Graham told MNT that in her previous research , she had "found striking gender differences in factors associated with frequency of masturbation in men and women. Measuring an average time to ejaculation is not a straightforward matter. Graham's study who found it easy to talk about sex with their partner were more interested in sex.