What do flies and the Matrix have in common? Recent research (and catching up on some 90s DVDs) suggests it’s the ability to avoid fast-moving objects by watching them in slow motion. Whether it’s Neo dodging bullets in bullet time, or a Musca domestica dodging a newspaper at lunchtime, both can observe speeding objects moving as though through treacle.
Indeed, it’s not just flies – time perception appears to be directly related to size across most species. In general, the smaller the animal, the faster its metabolic rate, and the slower it perceives time passing.
The research involved flashing lights at animals and recording how quick the flashes had to be before they apeared to merge into a constant lightsource. Flies, apparently, can distinguish lights flickering four times faster than adult humans, but children may also be ahead of their parents. And while this may have ramifications for TV image refresh rates (no, seriously, think about it), the ability to perceive time in slo-mo may, more importantly, mean the difference between life and death for smaller creatures. In the surely immortal words of Professor Graeme Ruxton from St Andrews: “Flies might not be deep thinkers, but they can make good decisions very quickly.”
There may be another benefit to differentiating time perception. As Dr Luke McNally, University of Edinburgh, explained, many species such as fireflies use flashing lights as signals. If their larger, slower predators can’t keep up with these signals, the fireflies effectively have a secure method of communication which won’t result in them getting eaten.