A study comparing the speed of visual information processing in 237 species found that flight, prey pursuit, and bright environments are associated with the ability to perceive rapid changes. However, the measure does not prove that time itself passes differently for them.
An attempt to swatt a fly often ends with the insect disappearing before the hand can reach it. It has no ability to predict the future, but its visual system is capable of detecting changes much faster than the human eye can perceive. For it, the movement of the hand may provide a longer sequence of visual images to respond to.
A large comparative study, which included data from 237 species – from jellyfish and starfish to insects, fish, birds and mammals – found that the rate at which animals process visual information is related to their lifestyle. Flying animals, predators that chase prey and species that operate in brightly lit environments tend to notice changes that occur over shorter time periods.
The study, conducted by researchers from Trinity College Dublin and University College Galway, is published in the journal Nature Ecology & Evolution. It provides broad support for the idea that evolution adapts the speed of sensory systems to environmental demands.
To compare the species, the researchers used a measure called Critical Flicker Fusion Frequency, or CFF. In such an experiment, the animal is presented with a light that flashes on and off at an increasing rate.
Initially, each flicker can be distinguished individually. When the flicker rate exceeds a certain threshold, the visual system no longer separates the flashes, and the light appears continuous. The higher the threshold, the faster the animal can perceive changes.
Humans are also familiar with the phenomenon. A movie, a computer screen, or an LED light actually displays a sequence of images or fluctuations in light, but above a certain rate they merge in our eyes into a stable image. In humans, the threshold of discrimination varies according to lighting conditions, contrast, and the location of the stimulus in the visual field, but it is common to talk about the order of magnitude of about 60 flashes per second under certain conditions.
Fast insects are capable of much higher rates. Dragonflies and flies have been measured to have rates of hundreds of blinks per second in some cases. This does not mean that they think hundreds of thoughts per second, but rather that their visual system can provide the brain with updated information at an exceptionally high frequency.
One of the most striking findings in the study was the connection to flight. On average, flying animals had a visual temporal resolution about twice as high as that of non-flying animals.
A fast-flying animal needs sharp, fast vision.
The advantage is clear: a fast-flying animal must detect obstacles, changes in direction, predators, and prey within a fraction of a second. A dragonfly chasing an insect in the air cannot be satisfied with a slowly updating image. A small deviation in the prey's trajectory can determine whether the chase ends in a meal or a miss.
The researchers also found that stalking predators—animals that actively pursue fast, maneuverable prey—tended to process visual information more quickly than species that feed on plants or non-fleeing food. In the aquatic environment, there is an advantage for small, highly maneuverable species that need to track movement in three dimensions.
At the other extreme are slow-moving animals, such as starfish and certain deep-sea species. For an animal that moves slowly and feeds on a stationary food source, investing energy in an extremely fast visual system is not necessarily worthwhile.
Rapid information processing is not free. Sensory cells, nerves, and fast brain networks consume a lot of energy. Therefore, evolution is unlikely to develop such a system unless it provides a real advantage in survival or reproduction.
Not just vision
There is no way to ask a fly if a second seems longer to it, and there is no certainty that a high flicker threshold means that the entire world is experienced as a slow-motion scene. Time perception also includes memory, attention, estimation of durations, biological clocks, and the processing of sounds, smells, and touch – not just vision.
So it's more accurate to say that different species live in visual worlds with different time resolutions. A dragonfly can extract useful information from events that are too fast for us, while a slow animal might not notice some of the changes that a human sees.
Does an LED light flash in the eyes of animals?
The findings also have practical implications. Bulbs, screens, and artificial lighting may appear continuous to humans, but flicker to the eyes of animals with higher temporal resolution.
Such flicker can affect the ability of birds, insects, and fish to navigate, hunt, or detect predators. It can also disrupt animal experiments: lighting that appears perfectly normal to a researcher can create a flickering visual environment for the animal.
The researchers believe that lighting design in nature reserves, breeding facilities, aquariums, and urban environments should take into account not only human vision, but also the visual systems of the species exposed to it.
The study reminds us that the world we see is not a neutral, complete version of reality. It is the product of a sensory system that evolved according to human needs. A fly, a bird of prey, a fish, and a starfish share the same physical time with us – but each of them receives a different sequence of information from it.
FAQ
Do flies really see the world in slow motion?
Flies' visual systems can detect changes more quickly than humans. This can be compared to slow motion, but there is no evidence that their subjective experience is the same as watching a slow-motion film.
How do you measure an animal's visual speed?
The highest rate at which the animal still perceives a light to be flashing is measured. Above this threshold, the flashes merge and appear as continuous light.
Which animals process visual information the fastest?
Flying insects, fast birds, and predators chasing prey tend to have high visual temporal resolution. Dragonflies and flies are among the fastest species measured.
Why don't all animals have fast vision?
Rapid processing requires a lot of energy and sufficient light. It is especially beneficial for species that fly, chase prey, or need to quickly evade predators.
Can LED lights appear flashing to animals?
Yes. Lighting that appears steady to humans may be perceived as flickering by birds, insects, or other animals with higher temporal resolution.
More of the topic in Hayadan:
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I read with great interest, fascinating. Thank you very much.
Thanks. Due to a mistake, I uploaded an initial version to the site. Now I hope everything has been fixed.
my father
Full of spelling errors, urgent proofreading
A few errors 🙄
Mannequin Bird from South America:
The courtship dance is fast – a person can only notice it in slow motion after being filmed on camera at 500 fps.
The dance features very high-pitched, varied sounds produced by 80 wing beats per second (not a chirp) – faster than a hummingbird's fluttering.
An impressive dance that consists of a set of fixed movements such as walking quickly backwards and sideways, short jumps, etc.
Their brains react much faster than a human brain, a split second (in human terms) is a long and eventful time for them.
What about proofreading?