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Fly’s ‘Slow Motion’ Vision

How can flies avoid being swatted? Scientist studied on animals ‘perception on high frequency light and discovered that flies use the same way to avoid swatter like Keanu Reeves dodges flying bullets in the Movie Matrix—by watching time pass slowly.

How fast is the rapid swatter in the view of flies? Maybe as fast as the cars in the right above figure. There is no doubt that they have enough time to escape.

In fact, fly is not the only species that perceive time in a different scale from humans. Latest research suggests that among various species, the perception on time is directly related to size—the smaller the size is and the faster the metabolism rate is, the slower time passes.

 So, how to measure different animals’ ability to perceive time? Here comes an important evidence called “critical flicker fusion frequency”, which is the point at which the flashes seem to merge together so that a light source looks like constant. This value provides an indication of animals’ ability of time perception. The images on TV, computer and cinema screens are all flickering, but we perceive them as they are continuous due to their high frequencies.

“Many researchers have studied at this in various animals by measuring their perception of flickering light,” said Dr. Andrew Jackson, the director of the research from Trinity College Dublin in the Republic of Ireland. “Some animals could perceive fast flickers while others much slower, so we can imagine that a fly literally seeing everything in slow motion.”

The article has been published on the journal Animal Behavior, in which they pointed out that smaller and more agile creatures had the most refined ability in perceiving information in a unit of time.

Dr. Jackson believes that this might account for the way time appears to speed up when we are getting older.

“Interestingly, we think that for children, time passes more slowly than it does for adults, and there are some evidence that it might be true.” Said Jackson, “There are research shown in humans that flicker fusion frequency is related with a person’s subjective perception on time, and it evolves with age. It is for sure that this value is faster in children.”

Scientists believe that time perception is just another aspect of survival and evolution.

“Animals’ ability to perceive time is of great importance.  To perceive time at very small scales sometimes is the difference between life and death for some small and agile animals, and our results support to this point,” said Kevin Healy, the co-author of the article and a PhD student at the School of Natural Sciences at Trinity College Dublin.

Professor Graeme Ruxton from the University of St Andrews in Scotland, also took part in the research, noted:” Having eyes that can transmit updates to brain at higher frequencies than our eyes is of little value if the brain is not able to process the information equally quickly. Therefore, this study highlights the amazing capabilities of even the smallest animal brains.”

“Flies may not be deep thinkers, but they could make quick and wise decisions.”

Another member of the team, Dr. Luke McNally, from the University of Edinburgh, noted that some animals can exploit differences in time perception to their advantages. “For an instance, many species can use flashing lights as signals, like fireflies and many other deep-sea animals. Larger and slower predator might be unable to decode the signals if their visual system is not fast enough, offering a secret channel of communication for the signalers.

This research covered more than 30 species including rodents, lizards, eels, pigeons, chickens, dogs, cats and leatherback turtles. The latter species listed here have larger size and slower metabolism rate, and hence time passes relatively faster for them.


 What does TV looks like in a dog’s eyes? Image source: usahitman.com

The following numbers represent how many unit information could be processed by other species at a unit time for human:





European  eel


Blacknose shark

Tiger salamander











So dog owners might be surprised to know that their dogs can see TV flickers, said Dr. Jackson. They have a visual system that refreshes at higher rate than TV screen does.

 SourceYahoo News UK & Ireland.

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