How do animals see the world?

How sharp do people have when compared to animals? Scientists from Duke University asked this question and conducted a study comparing the visual acuity in humans and various animals. At the same time, with the help of a special program, even images were created showing how blurred or clear the world can be to some animals.


Images showing visual acuity in (from top to bottom and from left to right) of a person, a cat, a goldfish, a rat, a fly and a mosquito

In the animal kingdom, most species “see the world with much less detail than we do,” notes Eleanor Caves, co-author of the new work. Of course, scientists do not have the opportunity to ask animals to read letters in the optometric table: instead, they study the anatomy of the eyes and conduct behavior tests to determine the visual acuity of certain animals.

This time, the researchers used a method in which the parameter “cycles per degree” (cycles per degree) was measured to determine visual acuity. Then this information was processed in a special program, in which after that images were created demonstrating how clear or blurred the world is to the animal under investigation.

People distinguish approximately 60 cycles per degree – that is, 60 pairs of black and white parallel lines per one degree of angle of view. In this case, as the researchers found, chimpanzees and other primates – about the same indicator as we do. Some birds even outnumber people: for example, the wedge-tailed eagle is able to see 140 cycles / degree – such sharp sight, obviously, helps him to notice at a height of thousands of meters of prey on the ground.
 

 
In most other animals, vision is much less acute than in humans, as the researchers found. So, many fish and birds see about 30 cycles / degree, and elephants – only 10 cycles / degree. The last indicator is already the level of blindness for a person, but in many animals and insects it is even lower.

The study, as noted, also helps to better understand the ecology of animals. For example, butterflies can hardly distinguish color patterns on each other’s wings, however birds are capable of this. The same applies, for example, to shrimp-cleaners: color patterns of their color and antenna attract fish, whose parasites shrimp-cleaners eat; while shrimps, as the researchers write, can not distinguish between color patterns, even at a distance of two centimeters.

In the new study, scientists have so far considered only the ability of the eyes of certain animals. It is important to note that animals can actually see the world better – thanks to the image processing in the brain. This mechanism was not considered in the new paper. Although, of course, as Caves notes, if the visual acuity is too low to detect a particular detail, the brain is unlikely to be able to process it in any way.

The study was published in the journal Trends in Ecology and Evolution, briefly reported by ScienceAlert.