Color perception: characteristics, functioning and alterations.

An overview of how color perception works in humans.

Although it may seem objective, color is a private and therefore subjective perceptual experience (just like the perception of pain). But... What does color perception involve? What makes us perceive a red, a blue or a yellow color?

In this article we will talk about how colors are perceived, the different colors and the pathologies associated with color perception, among other topics.

What is color?

There are different definitions for color. Color can be understood as a perceptual response to objects and lights that confers certain qualities to them (as for example, green). It can also be considered a characteristic of the perceptual response.

To define colors, in our everyday life we often use examples (such as "blue is like the sea", "green is like trees" or "black is like darkness".

Factors that determine color perception

There are four important factors when perceiving colors. These are:

• Wavelength and illumination.Wavelength and illumination: that is, how objects reflect light.
• The effect of the surrounding areaalso called simultaneous contrast.
• The level of adaptation of the observer: presence of light or darkness (the darker it is, the more we perceive blue [short wavelength]).
• Color memoryThe knowledge of the characteristic color of certain objects influences our perception.

Color constancy

On the other hand, color constancy also plays a key role in color perception; it implies that we perceive colors "always" the same (under natural conditions), i.e. red for us will always be red for example.

However, this constancy is only partial, since color perception changes a little when the illumination changes..

How do we perceive colors?

The colors we perceive are the result of the mixture of the wavelengths reflected by objects; it can be said that light is filtered by the surface on which it strikes.. There are three types of wavelengths:

• Short wave: blue color.
• Medium wave: green color.
• Long wave: red color.

The remaining colors (different from these three) result from the mixture of these three wavelengths.

The perceptual process

Visual perception is determined by neural processing at all stages of the visual system.. This depends on the cones, among other variables.

At the physiological level, there is a selective discoloration of visual pigments in chromatic adaptation. This involves specific neurons in a particular area of the brain, area V4, located in the extrastriate cortex (secondary visual cortex).

Striatal neurons respond to visual stimuli; this response is related to the wavelength (which determines the type of color (which determines the type of color we see), and the response of the V4 neurons is related to perception.

Types of colors

There are two types of colors:

1. achromatic.

These colors have no hue; they are black, white and grays. At the cerebral level and from sight, we perceive achromatic colors with rods (receptors), which are photoreceptor cells of the retina responsible for vision in a low condition. responsible for vision in low light conditions.

2. Chromatics

The chromatic colors are nuanced: they are all "other colors", such as blue, red, green... Unlike the previous ones, the receptors of these colors are the cones, the receptors of these colors are the cones (photosensitive cells located in the retina, responsible for perceiving colors in one way or another).

Functions of color perception

Color perception has a number of functions for humans, but also for some animals (since not all see in color). Let's get to know them:

1. adaptive

Perceiving colors implies a value for survivaland therefore an adaptive value, since it allows: searching for food, detecting dangers and interpreting emotions.

The perception of color is the result of an evolutionary development (for example, the fact of detecting fruit among the foliage increases the probability that the animal has food, eats, and therefore survives).

2. Aesthetics

The fact of perceiving colors means being able to appreciate beauty and aesthetics, as well as to appreciate the nuances of objects, landscapes, art, etc. and aesthetics, as well as appreciating the nuances of objects, landscapes, art (e.g. in paintings), people, etc. (e.g. in paintings), people, etc.

3. Perceptual organization

Perceiving different colors makes it possible to organize the world by separate areas or segments.

Associated vision pathologies

The basic disturbance of color perception is color blindness.. This alteration implies that the person sees some colors different from the rest of the people, and "confuses" or interchanges some of them, or directly sees in black and white.

It is an alteration of genetic origin in the ability to distinguish colors, which affects 8% of males and 1% of females (because it is recessive linked to sex). Two types are known:

1. monochromatism

The first type of color blindness is a rare form of color blindness. a rare form of color blindness (total color blindness), which occurs in 10 people out of a million. Affected persons do not have functional cones, i.e. they show vision only with rods; they see in white, black and gray. On the other hand, they need protection from sunlight.

2. Dichromatism

The other type of color blindness involves blindness for some colors. It is sex-linked, and three subtypes are known three subtypes are known: protanopia, deuteranopia and tritanopia..

Deuteranopia

It is the absence of retinal photoreceptors of green color (medium waves). They see the same colors but with a different neutral point.

Protanopia

It is the total absence of the retinal photoreceptors of the red color (long waves).

Tritanopia

A very rare condition in which the blue (short-wave) retinal photoreceptors are absent. This is very rare.

Bibliographic references:

• Monserrat, J. (1998). Visual perception. Biblioteca nueva Psicología Universidad. Madrid
• Goldstein, E.B. (2006). Sensation and perception. 6th edition. Debate. Madrid
• Manzanero, A. Psychology of perception. Complutense University of Madrid (UCM).