How Do Humans and Animals See Colors Differently?
Color vision is the tendency of animals to distinguish amongst various wavelengths of light, regardless of the intensity of light. Color perception is a part of the broader visual system and is regulated by a complex neuronal mechanism that starts with brightness entering the eye causing differential activation of various types of photoreceptors.
These photoreceptors, therefore, produce outputs that travel through several layers of neurons before reaching the brain. Most animals have colour vision, which is regulated by common fundamental processes involving common kinds of biological molecules and the complex evolutionary background of various animals taxa.
Color vision in primates might have evolved in response to selective pressure for a multitude of distinct activities, such as foraging for ripe fruit, healthy young leaves, and flowers, and also identifying predator camouflage and emotional states in several other primates.
Wavelength
When white light was separated through its component colours through a dispersive prism, Isaac Newton demonstrated that they can be integrated to create white light by transferring it via a separate prism. The visible light spectrum spans the wavelength range of 380 to 740 nanometers. This spectrum includes spectral colours like red, yellow, blue, orange, cyan, green, and violet.
The following spectral colours belong to a group of wavelengths:
red, 625–740 nm;
yellow, 565–590 nm;
orange, 590–625 nm;
violet, 380–450 nm;
cyan, 485–500 nm;
green, 500–565 nm;
blue, 450–485 nm.
Infrared and ultraviolet are the terms for wavelengths that are greater or smaller than this range. Such wavelengths are invisible to humans, but they are visible to other species.
Color in the Human Brain
Initial colour opponent processes initiate colour detection in the visual system (even inside the retina) at an early stage. Both Helmholtz's trichromatic hypothesis and Hering's opponent-process hypothesis are right, however, trichromacy occurs just at the receptor level, while competitor processes occur at the retinal ganglion cell level and even beyond.
The opposing colour effects of blue-yellow, red-green, and light-dark are referred to as opponent processes in Hering's theory. The function of various receptor forms in the visual system, on the other hand, is in opposition. L and M cone activity, which roughly correlates to red-green opponency, however, appears to be running through an axis across blue-green to magenta, is opposed by certain midget retinal ganglion cells.
The input from the S cones is opposed by the input from the L and M cones in tiny bistratified retinal ganglion cells. It can also be confused with blue–yellow opposition, but somehow it simply follows a color axis from yellow-green to violet.
The Subjectivity of Color Perception
Color is a function of a viewer's visual perception. The wavelengths of visible light in the visual spectrum and human perceptions of color have a complicated relationship. Because most individuals are believed to get the same mapping, philosopher John Locke recognized that other possibilities exist and identified one of them with the "inverted continuum" thought experiment.
Somebody with a reversed spectrum, for instance, would see green when seeing 'red' (700 nm) light and red when seeing 'green' (530 nm) light. However, this reversal hasn't ever been observed in a laboratory environment.
Chromatic Adaptation
Color constancy, or perhaps the capacity of the visual system to retain the presence of an item under a broad variety of light sources, is referred to as chromatic adaptation in colour vision. A white page on pink, blue, or purple beam, for instance, may represent predominantly pink, blue, or purple beam to the eye; nevertheless, the brain compensates for the effect of illumination (depending on the colour change of nearby objects) and interprets the page as white even under 3 situations, a process known as colour constancy.
Color Vision in Non-Humans
Many animals could see a light spectrum that isn’t part of the "visible spectrum" for humans. Numerous insects, including bees, can sense ultraviolet light, that aids themselves in finding nectar in flowers. Plants which rely on insect pollination may be more effective at reproducing because of ultraviolet "colours" and patterns than because of how colourful they seem to human beings.
Birds, like humans, could see in the ultraviolet range (300–400 nm), and certain species have sex-specific patterns on their plumage which are only apparent in the ultraviolet range. However, many species who could see in the ultraviolet spectrum are unable to recognise red light or several other reddish wavelengths. The visible spectrum of bees, for instance, finishes approximately 590 nm, just before the orange wavelengths begin.
Birds, on the other hand, can see certain red wavelengths, but not as many as humans could. The popular goldfish may not be the only species that could see infrared and ultraviolet beam; their colour vision reaches into the ultraviolet although not into the infrared.
Evolution
Color perception processes are heavily influenced by evolutionary influences, the most important of which would be considered to be the ability to recognize food sources. Color vision is important for herbivorous primates to locate suitable (immature) leaves. Color is also used by hummingbirds to identify different flower kinds.
Nocturnal mammals, on the other side, have very little evolved color vision because cones need enough light to work effectively. Ultraviolet light appears to play a role in color perception in a variety of animal species, particularly insects.
The optical spectrum, in particular, comprises the most popular electronic transformations in the matter and is thus very useful for gathering environmental data.
Color Blind
Color blindness (Color blind) is a condition in which a person's tendency to see colour or colour variations is impaired. It can make it difficult to do things like pick ripe fruit, dress properly, and read traffic lights. Few educational practices can become more complicated if you are colour blind. Nevertheless, many color-blind people adapt, and issues are usually mild.
Red Green Color Blindness:
Protanopia, protanomaly, deuteranopia, and deuteranomaly are hereditary types of Red green color blindness that impact a large percentage of the population. Owing to the absence or mutation of the red or green retinal photoreceptors, those impacted may have trouble distinguishing between red and green hues. Since the genes for the red and green colour receptors are found on the X chromosome, where men have just single and females have two, hereditary red–green colour blindness affects males far more frequently than females.
Color Blindness Treatment:
If the colour vision disorder is caused by the use of such drugs or eye disease, there are no therapies for most forms of colour vision issues. Color blindness treatment and better colour vision can be achieved by discontinuing the medicine that is causing the vision disorder or managing the underlying eye condition.
Type of Color Blindness
Below mentioned are the types of color blindness:
Red and green color blind
Blue yellow color blind
Total color blindness
FAQs on Understanding Color Vision in Biology
1. What is the definition of color vision in biology?
Color vision is the biological ability of an organism to distinguish objects based on the different wavelengths of light they reflect, emit, or transmit. This perceptual property is not an intrinsic quality of an object but a result of how our eyes and brain process light. It relies on specialised photoreceptor cells in the retina to interpret this information.
2. What is the biological basis for color vision in the human eye?
The biological basis for color vision lies in the retina of the eye, specifically with two types of photoreceptor cells: rods and cones. While rods are responsible for vision in low light (scotopic vision), it is the cone cells that are responsible for color perception (photopic vision). These cones contain light-sensitive pigments called photopsins, which are stimulated by different wavelengths of light.
3. What are the types of cone cells in the human eye and what colors do they primarily detect?
Humans typically have trichromatic vision, meaning we have three types of cone cells, each sensitive to a different range of light wavelengths. These are:
L-cones (Long-wavelength): Most sensitive to light in the red range of the spectrum.
M-cones (Medium-wavelength): Most sensitive to light in the green range of the spectrum.
S-cones (Short-wavelength): Most sensitive to light in the blue range of the spectrum.
The combined stimulation of these three cone types allows the brain to perceive the entire color spectrum.
4. Which theory best explains the mechanism of color vision in humans?
Modern understanding of color vision relies on a combination of two theories. The Trichromatic Theory (Young-Helmholtz) correctly proposes that color perception begins with the three types of cone cells (red, green, blue). However, the Opponent-Process Theory explains the next stage, where the nervous system processes these signals in an antagonistic way. This theory posits three opposing channels: red vs. green, blue vs. yellow, and black vs. white, which explains phenomena like afterimages.
5. If humans only have red, green, and blue cones, how can we perceive colors like yellow or purple?
We perceive intermediate colors through the simultaneous stimulation of different cone types at varying intensities. For example, when both the red (L-cones) and green (M-cones) are strongly stimulated, the brain interprets this specific combination of signals as the color yellow. Similarly, the perception of purple arises from the stimulation of both red and blue cones. The brain's ability to interpret the precise ratio of signals from all three cone types is what allows us to see millions of distinct colors.
6. How does the brain create a complete color image from the signals sent by the cone cells?
The process involves multiple stages beyond the retina. After the cone cells are stimulated by light, they send electrical signals through retinal ganglion cells and the optic nerve to a region in the brain called the thalamus. From there, the signals are relayed to the visual cortex in the occipital lobe. Here, the brain performs complex processing, comparing the inputs from different cone types (opponent-processing) and integrating information about shape, motion, and context to construct the final, coherent color image we perceive.
7. Why can some animals, like bees and birds, see colors that are invisible to humans?
The range of colors an animal can see is determined by the types of photoreceptor cells in its eyes. Many animals possess different types of cones than humans. For instance:
Bees have cones sensitive to ultraviolet (UV) light, allowing them to see patterns on flowers that are invisible to us.
Many birds are tetrachromats, meaning they have four types of cones (including one for UV light). This gives them a far more complex and vibrant perception of color, which is crucial for finding mates and food.
Conversely, animals like dogs are dichromats (two cone types), resulting in a more limited range of color vision compared to humans.
8. What is the difference between color vision deficiency and complete color blindness?
These terms are often confused. Color vision deficiency is the most common condition, where an individual has difficulty distinguishing between certain colors, typically red and green. This occurs because one or more of the cone cell types are either faulty or missing. In contrast, true color blindness (monochromacy) is an extremely rare condition where a person lacks all functional cone cells and can only see the world in shades of grey, black, and white, relying solely on their rod cells.
