Scientists at Trinity College Dublin say the humble housefly manages to escape being swatted by rolled-up newspapers because time is in the compound-eye of the beholder.
The study, published in the journal 'Animal Behaviour', found that time is perceived at different rates across animals – so when a newspaper looms, the fly sees it coming in slow motion and can easily get away.
Kevin Healy, lead author of the study and a PhD student at Trinity, explained that researchers took the body mass and metabolic rates of 34 species of vertebrates.
"We found that small things with high metabolic rates, meaning they burn a lot of energy, see time faster. How they see things is like in slow motion for bigger animals."
The evidence comes from research into the ability of animals to detect separate flashes of fast flickering light.
Flies perceived light flickering up to four times faster than humans and therefore experience time in slow motion.