Life … moves … in … slow … motion … for … little … critters … like … flies

The smaller the creature and the faster its metabolic rate, the slower it perceives time, say a group of researchers from Ireland and the UK.

"Animals smaller than us see the world in slo-mo," study leader Andrew Jackson from Trinity College Dublin told The Telegraph. "It seems to be almost a fact of life."

Jackson and his colleagues, who published their findings in a paper in the journal Animal Behaviour entitled "Metabolic rate and body size are linked with perception of temporal information", based their findings on data from 34 species, from Ambystoma tigrinum to Tupaia glis – that would be the tiger salamander to the common tree shrew, to us non-bioboffins.

The study focused on how fast each creature can perceive individual flashes of light, and at what point those individual flashes fuse into one steady light – the "critical flicker fusion frequency" (CFFF), to be precise.

We humans, for example, have a CFFF of around 60Hz when young and healthy, but that rate lowers as we age. Spermophilus lateralis, aka the golden-mantled ground squirrel, on the other hand, has a CFFF of 120Hz – and so according to Jackson and his team, that cute li'l critter perceives the world and its inhabitants to be moving half as fast as we see them.

"Our focus was on vertebrates," Jackson said, "but if you look at flies, they can perceive light flickering up to four times faster than we can. You can imagine a fly literally seeing everything in slow motion."

Jackson and his fellow authors postulate that the differences in temporal perception have their evolutionary roots in the visual requirements for predators and prey. That ground squirrel's slo-mo world, for example, allows it to perceive slower and finer-grained movement detail than can the Asio flammeus – short-eared owl – that would like to invite it to dinner; the owl has a CFFF of 70Hz.

Or, as one of the paper's coauthors put it, "Our results lend support to the importance of time perception in animals where the ability to perceive time on very small scales may be the difference between life and death for fast-moving organisms."

But it wasn't the tense relationship between predator and prey – or fly and flyswatter – that inspired Jackson's research. He says that he was motivated to conduct the study because he noticed that small children are always in a hurry.

"It's tempting to think that for children time moves more slowly than it does for grown ups, and there is some evidence that it might," he told The Telegraph. "People have shown in humans that flicker fusion frequency is related to a person's subjective perception of time, and it changes with age. It's certainly faster in children."

In other words, if you're middle-aged and time seems to be flying by, you now have a physiological basis for that feeling.

The study also shows that even tiny-brained beasts such as flies can process binary nerve-firing visual impulses at a rapid rate – an impressive feat of neural activity. As another of Jackson's colleagues put it, "Flies might not be deep thinkers, but they can make good decisions very quickly." ®