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Time flies when you talk dirty to me (and perhaps when I consider other erotic material as well). Judging how long something lasts is difficult. Sometimes time drags along and the clock seems stuck. On other occasions, time zips along without our awareness.
In a paper published this fall, Jason Tipples documented that people underestimate how long sexually explicit words were presented on a computer screen. His research expanded on similar findings by other researchers. In particular, Hawkins and Tedford (1976) found that people think a recording describing sex went by more quickly than a bland passage from a textbook (maybe you've noticed that reading a textbook seems to take forever). In addition, Angrilli and his colleagues (1997) found that people underestimate how long erotic pictures are presented but overestimate the presentation time of very unpleasant pictures (of things like bloody wounds). People underestimate the presentation time of erotic words, stories, and pictures. Wow, that was fast, can we see it again?
Tipples argued that two factors combine to influence how people judge time's passage. To start, most researchers assume that everyone has something like a biological clock ticking away and that we judge time by tracking how many ticks that biological clock takes. More ticks = more time. The first factor to influence time perception is physiological arousal. As arousal increases, the biological clock speeds up. This means more ticks by your clock in a given amount of time - so instead of 60 beats during 1 minute, your clock is cranking out 120 beats because you are aroused. In general, you will perceive more time passing when you are aroused, because your clock is so busy.
Fighting against the speedy biological clock is your attentional focus. If you are distracted by something really interesting, then you may not be able to track how many beats your biological clock is cranking out. Sex is interesting (that's why you're still reading), so you may not keep track of your clock when viewing erotic material. Even if that clock is really cranking out the beats, you won't be aware of time passing because your attention is devoted to sex. Of course with boring material, you are aware of every beat of your biological clock and how long something takes.
In contrast to sexually prurient material, very gross pictures have a different effect for most of us. Those pictures also arouse, so your biological clock speeds up. But your attention doesn't want to focus on those pictures and you therefore do a better job of keeping track of your clock - lots of beats, my gosh, when is that awful picture going to be turned off?
Angrilli and his colleagues summed this up rather nicely. The erotic pictures or words attract attention, you are less aware of time, the pictures seem to be removed quickly, and you wish you could look longer. Gross pictures allow you to be aware of your quickly beating clock, seem present for too long, and you wish those pictures would go away.
So talk dirty to me and it makes the time fly. Erotic pictures and stories seem to disappear quickly as well. As far as I know, nobody has studied time judgments for the sex act itself. But since sex is arousing and generally interesting, maybe people will underestimate how long that will take as well. Finally an excuse for when your partner complains that it didn't take very long. Simply explain that she (or he) misjudged time because she (or he) found the event far too interesting and enjoyable.
