Time is nothing but the speed at which animals/humans process sensory information. This can be measured by how fast they can detect flickering lights.
Imagine you are observing a flickering light source that is emitting, say, 5 flashes per second. You can easily see each individual flash clearly separated by fleeting instants of darkness. However, as you start to increase the rate of flicker, you will reach a frequency where the light flickers so fast that you can no longer distinguish the distinct flashes but you start seeing a steady or continuous light instead. That critical flickering speed is called the Flicker Fusion Frequency (FFF) and is a measure of our brain’s ‘recording’ speed.
Generally, the smaller the animal and the faster its metabolic rate, the faster the flickering light it can detect, the faster it can process sensory information, and the slower time passes.
Have you ever wondered how birds manage to chase one another through a forest at lightning speeds without colliding with branches or ending up splattered against a tree? Animals smaller than us see the world in slow motion. That is how birds manage to avoid smashing into trees. Scientists, for instance, found that a pigeon’s brain can record up to 100 frames per second (100 Hz) and ground squirrels can grasp 120 Hz. For fish, the flicker fusion speed is around 60 to 80 Hz.
A higher FFF gives animals an advantage when pursuing a fast-moving target. Pigeons rely on the high recording speed to flee from a predator, dive down to snatch prey, or zero in on a nest for precise landing. It allows them those few extra seconds to peck at seeds on the road and fly away at the last possible moment before a car approaches.
Dogs can also process visual information at least 25 percent faster than humans. If you own a dog, you may be surprised to know that when your pet is sitting next to you watching TV, it sees a flickering screen. That is because TVs flicker at 30 Hz but provide the illusion of continuous images because of our lower temporal resolution compared to the higher frequencies at which they operate. Dogs, however, can detect that flicker because their visual system has a higher refresh rate than that of TV screens. You might think they are enjoying the movie, but all they can see is constant flicker, they just enjoy your company! For them it would probably be more enjoyable if the movie was played on a computer monitor because of its higher flickering frequency (60 Hz).
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Similar studies on shark vision have revealed that they experience flicker fusion at about 45 Hz, nearly twice the frequency at which humans cease to see distinct flashes. Chickens can perceive flickering at around 90 Hz. This means they can easily detect the flickering of florescent lamps that are generally used to artificially illuminate poultry housing farms, creating unnecessary and constant stress for these poor animals.
The highest FFF in animals belong to insects, like houseflies and honeybees, which can perceive motion at the colossal rate of up to 300 Hz. This remarkable recording speed is what makes it so hard to hit a housefly with a rolled-up newspaper. The fly perceives the swift strike in ‘bullet time’, similar to a slow-motion action scene in movies like The Matrix. For a fly, time runs at least 20 times more slowly than it does for humans. This gives it ample time to escape and easily evade the strike in the same way that Keanu Reeves evades the bullets in that famous scene. Flies might not be deep thinkers, but they can make good decisions extremely quickly.
At the other end of the spectrum, lower Flicker Fusion Frequencies can be found in animal species that have a slower pace of life. The leatherback sea turtle, for instance, has an FFF of just 14 fps. Snails are in a similar range. The lowest known FFF belongs to a deep-sea creature (the Booralana Tricarinata) which boasts only 4 fps. Its temporal resolution is so low that it is unlikely it could track any moving objects. For these species, life looks like one brief and boring slide show!
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