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A comparison of 138 species finds that dragonflies perceive changes in their environment five times faster than humans and 400 times faster than starfish
Life
20 December 2022
Dragonflies can see in “bullet time” Shutterstock/boyphare
Fast-moving creatures – especially small animals, animals that fly and top ocean predators – perceive time more quickly than others. That is, they can process more frames per second than slow-moving animals lower in the food chain, such as starfish, according to a comparison of more than 100 species.
“We already know that different animals perceive time differently from us,” says Kevin Healy at the University of Galway in Ireland, who presented the results at a meeting of the British Ecological Society on 20 December. But he wanted to find out, “If you’re a predator, do you have faster eyes than if you’re an herbivore?”
He and his colleagues began by reviewing previously published research on the flicker fusion test, a common measure of the rate at which animals perceive the passage of time. During the test, researchers increase the frequency of a flashing light until an animal sees it as a continuous glow, indicated by the reaction of light receptors in an animals’ retina.
“It’s kind of like measuring the frame rate of your eyes,” says Healy. Humans, for example, can detect light flickers at speeds up to 65 flashes per second. That means they can perceive changes in their environment 65 times per second.
A crown-of-thorns starfish feeding on coral Shutterstock/Richard Whitcombe
When they compared 138 different species, they found that the crown-of-thorns starfish (Acanthaster planci) notices changes at the slowest pace, registering just three flashes every four seconds, averaging less than one flash per second.
“In their world, everything is just a blur,” Healy says. The starfish’s temporal perception may be so slow because it’s an herbivore – it doesn’t need to strike fast to get a meal. A tasty coral polyp will be in the same place even if it takes the starfish more than a second to find it. A marine predator such as a shark, on the other hand, needs to see faster to catch fish, which are constantly moving.
On average, flying animals detect light changes at a faster rate than land-bound animals, likely because they need to be able to sense changes around them quickly to avoid collisions. “If you fly, you see faster,” Healy says.
Healy’s research found that dragonflies can perceive changes in their environment the fastest, detecting 300 flashes per second – about five times faster than humans and 400 times faster than starfish. “It’s almost like bullet time in The Matrix,” says Healy, describing dragonflies’ time perception.
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