Although Darwin made some reference to the subject, the fact is that the first scientific approach to the problem was made by the painter and naturalist Abbott Thayer (1849-1921).

It was the first to describe the reason why many of the animals have a dark back and light belly.

Thus, the dam cancels its shadow and reduces the chance of being detected, because “the whole visual system is designed to find the edges of objects,” he explains about the ophthalmologist.

Similar to a photo editor

Functions as the tool to increase the contrast of a photo editor: When a ganglion cell (retinal neurons that form the optic nerve connecting the eye and stimulates the brain ), that inhibits stimulated neighboring ganglion cell. Thus image contrast is enhanced.

There are many optical illusions that are based on this mechanism. For example the optical illusion classic chessboard in which two squares colored with the same shade of gray take different appearance depending on which are located in a bright or shaded area.

Not to be seen, many animals sailors are transparent, others change color as cuttlefish and some that even disguise themselves using objects in the environment- the decorators crabs inserted into their exoskeleton elements of the environment (algae, anemones or pebbles) to hide -.

There are three strategies that are particularly important: crypsis, disruptive coloration and countershading. In the first case, the animals try to merge with the means adopting a luminance, color and similar to the texture environment, and in the second case the body divided by artificially high contrast bands rivaling the actual edges of the animal.

The countershading or countershading, one of the most used strategies

Finally, the mechanism of countershading or -described countershading by Thayer in 1896- is present in many animals and is “trying to override the shadows because they are a clue monocular very important in the perception of volume,” explains the doctor of Hospital Henares.

It is not unusual to be a painter the first to intuit the mechanism, because the shade is one of the tools of the visual system uses to give volume to objects, and precisely this is one of the most important elements used by painters to make a two-dimensional object appear three-dimensional.

Thayer realized that many animals use this trick in reverse. As in nature the main light source is the sun, the top of the object is illuminated, while the bottom is in shadow.

If the animal is colored in reverse (dark and light belly loin), the shadow is void and the animal flattens and becomes more difficult to detect.

Uniforms of soldiers, military ships …

Since the beginning of the century, the mechanisms of camouflage also interested governments to apply, for example, in designing the uniforms of the soldiers or the paintings of boats.

During World War I, the British and American governments decided to paint ships following highly contrasting geometric patterns.

This design is called “motion dazzle”. It is not camouflage in the strict sense because not hide the object but is believed to hinder the ability of the observer to perceive movement.

What it was therefore was shortstops mislead the German ships.

Technical “Motion dazzle” in an allied ship during the First World War. Photo Wikipedia (copyright free).

Anyway, adds the ophthalmologist, has never been fully demonstrated whether these techniques actually worked effectively on ships.

Some modern experiments suggest that high for the “motion dazzle” work speeds are required.

In fact, at the end of World War I, the British admiralty discussed the matter and came to no conclusion.

The truth, says Gonzalez, is that painted boats following the “motion dazzle” had been painted boats attacked the conventional way, but had been less sunk “.

“The explanation may lie in ships” disguised “were also higher tonnage, which were” easier to see but difficult to sink. ”