Although it may seem objective, color is a private perceptual experience and therefore subjective (like the perception of pain). But… what does color perception imply? On what does it depend that we perceive some colors and others? What makes us perceive a red, a blue or a yellow?

In this article we will talk about how colours are perceived, about the different colours and about the pathologies associated to colour perception, among other topics.

What is color?

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

To define the colors, in our daily life we usually use examples (such as “blue is like the sea”, “green is like the trees” or “black is like darkness”.

Factors determining color perception

There are four important factors in colour perception. These are:

  • The wavelength and illumination : that is, how objects reflect light.
  • The effect of the surrounding area : also 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]).
  • The memory of colour : the knowledge of the characteristic colour of certain objects influences our perception.

Color consistency

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), that is, red for us will always be red for example.

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

How do we perceive colors?

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

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

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

The perceptive 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, a selective discoloration of the visual pigments occurs in the color adaptation. This involves specific neurons in a particular area of the brain, the V4 area, located in the extra-striated cortex (secondary visual cortex).

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

Types of colors

There are two kinds of colors:

1. Achromatics

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

2. Chromatics

The chromatic colours have nuances: they are all “other colours”, such as blue, red, green… Unlike the previous ones, the receptors of these colours are the cones (photosensitive cells that are located in the retina, responsible for us to perceive colours 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 colours implies a survival value , and therefore an adaptive value, since it allows: searching for food, detecting dangers and interpreting emotions.

Color perception results from an evolutionary development (for example, detecting fruit among the foliage increases the probability that the animal will have food, eat, and therefore survive).

2. Aesthetics

The fact of perceiving colours implies being able to appreciate beauty and aesthetics, as well as appreciating the nuances of objects, landscapes, art (for example in paintings), people, etc.

3. Perceptual organization

Perceiving the different colors allows you to organize the world into separate areas or segments.

Associated Vision Pathologies

The basic alteration 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 exchanges some of them, or that he or she directly sees black and white.

It is a genetic alteration in the ability to distinguish colours, which affects 8% of men and 1% of women (because it is sex-linked recessive). Two types are known:

1. Monochromatism

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

2. Dichromatism

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

Deuteranopia

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

Protanopia

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

Tritanopia

It is a very rare condition in which blue (shortwave) 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)