Small creatures like squirrels and hummingbirds are under constant threat of being eaten. And it’s because of that risk, scientists reason, they have evolved to perceive the world at a fraction of the rate that larger species do—the world always appears to operate at a much slower temporal scale for these small creatures.
i09 describes the dynamic range of visual perception:
All you need to do to get this impression is simply watch the way a small bird, like a budgie, twitches as it scans its surroundings. What looks like near-spasmodic behavior to us is an animal that’s essentially working at a faster “clock rate” (so to speak). To them, humans, or larger predators, appear to move in slow motion; we likely appear impossibly slow and cumbersome through those eyes.
Researchers writing in the journal Animal Behavior confirmed this observation with a measurement called the critical flicker fusion frequency, or the lowest frequency at which an animal can tell a light is flickering rather than remaining constant. Animals’ abilities to perceive that flickering, they explain, is a proxy for their visual system’s rate of information processing. The team compiled the critical flicker fusion frequency from published scientific literature for around 30 species, including lizards, eels, chickens, leatherback sea turtles and cats. (Scientists determine that value by ”conditionally training an animal to respond to a change in its perception of a light flashing.”)
The faster the animals’ metabolism, the team found, the more adept it was at spotting rapid flickering. Flies, for example, can perceive visual stimuli four times faster than we can. “The generality of these findings suggest that temporal resolution may play a much more important role in sensory ecology than previously indicated, in particular because of its universal effects relating to body size,” the authors conclude. This explains why it’s so difficult to sneak up on a fly. Luckily, however, humans excel intellectually where we fail visually—that’s what fly swatters are for.
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