You're driving down the road, and you notice a black lump ahead of you. As you move closer, the lump's shape becomes clearer and starts resembling an animal. The closer you get, the more of the animal's features begin to shape your mind: black fur with some white spots, a tail, legs, a snout...it's a skunk! If you had known sooner, you would have put your car windows up to avoid the smell. Even though you could see the shape from a long distance away, you could not make sense of the shape until you moved closer.
- What is visual perception?
- How is visual perception different from visual acuity?
- What are different skills we need for visual perception?
- Why is visual perception important?
- How does visual perception work?
Meaning of Visual Perception
Beyond just sensing something in our environment, different parts of our bodies also work together with our senses (like seeing a lump in the road) to interpret what we are sensing: the different visual, auditory, tactile, olfactory, and gustatory information we receive from the environment. These are called perceptual skills, and making sense of visual information is specifically called visual perception.
Visual perception is defined as the ability of the eyes and the brain to interpret visual data received from the environment. Perception is distinct from acuity, defined as the ability to see clearly.
Difference between Visual Perception and Visual Acuity
Perception is about taking the information that has already been received by the senses and making sense of it. The specific cells in the eye receiving the light signals work together with nerves traveling up to the brain to make sense of the visual data.
Two people can see the same image but have different interpretations of it. Looking at the shapes in an optical illusion, one person may say that they're seeing the shapes moving in a clockwise direction, and the other person may perceive the shapes as moving counterclockwise.
Fg. 1 An optical illusion, pixabay.com
Either way, the person's perception of which direction the shapes are moving in is completely different from their vision's clarity. Even if both people looking at the image have 20/20 visual acuity, their perception of the image can still be different.
Visual Perception Skills
The skills your eyes need to use depend on the conditions within your environment. Are you sitting in a dark room with no window? Are you outside at a carnival during the day? The visual skills you use will be different, and your perception of what you're seeing will also be different. There are three types of visual skills that you should know:
Photopic Vision
You need your photopic vision skill during the daytime or in an environment with adequate lighting. Outside during the day or inside with the lights on, your eyes and brain sense and interpret the colors around you through specific cells in your eyes called cone cells.
Color Vision
Cone cells in human and animal eyes sense color by interpreting different wavelengths of light. The whole process of color perception is complicated, from the perception of light to the acceptance of the information by the photoreceptors and finally to the activation of specific neurons. Two theories that explain how we receive and interpret colors are trichromatic and opponent-process theory.
Trichromatic Theory
The trichromatic color theory, also known as the three-component theory, assumes that there are three primary colors: red, green, and blue (RGB). Thomas Young proposed in 1802 that our eyes have three sensors that detect different lengths of light waves. Then, 50 years later, Hermann von Helmholtz proposed that the cones of our eyes function to varying wavelengths of light. The activation and combination of these three types of cone cells produce a wide range of hues.
Opponent-Process Theory
According to this theory, eye sensors function in pairs: red and green, yellow and blue, and black and white. The activation of a color sensor disables its other pair. This theory explains how color afterimages and color blindness happen. When you stare at something yellow, the yellow sensor activates, and when you move your focus to a blank page, a blue afterimage appears. A missing receptor pair, such as red and green, makes it difficult to see red and green hues in the case of color blindness.
Fg. 2 Waves of color, pixabay.com
Scotopic Vision
You use your scotopic vision skill in dark or low-light environments. In these conditions, rod cells in the eye are activated, allowing for better visual data interpretation even in low-light settings. Cone cells in your eye perceive light in well-lit settings. They are also responsible for perceiving color. The cones of our eyes are grouped around the retina's center. A depression in the retina's center called the fovea includes the highest concentration of cones.
Rod cells in your eye perceive light in low-lit settings, but they do not detect colors. These cells are distributed all over the retina and are solely responsible for detecting black and white. The light-sensitive molecule rhodopsin, found in rods, is crucial for allowing vision in low-light conditions.
Mesopic Vision
Mesopic vision, or twilight visual perception, is the skill to detect and interpret data in semi-dark settings. Street lighting at night, outdoor night settings, and other environments with lower-light lamps will activate this visual skill. Experts believe that mesopic vision combines the use of rod cells and cone cells, or scotopic vision and color perception.
Depending on your setting, your eyes use different skills to receive information from your environment. How well these skills work varies from one person to another. One person may have an excellent photopic vision but struggle with color perception. Those who are color blind have a specific type of visual perception disorder involving the eye's cone cells.
Color blindness is the inability to see and tell colors like most people. When one or two color sensors (cones) of the eye is missing or faulty, it may be hard to detect colors. Rare instances of severe color blindness occur when only shades of gray are present. In mild color blindness, it is easy to see colors in good light conditions. Color blindness usually interferes with both eyes, and it remains stable over a lifetime.
Activities in Visual Perception
Vision first happens through the cornea, lens, and retina: the eye's sensory faculties. The cornea is the protective outer layer that focuses light on our eyes. The lens directs the light rays to the retina as light enters the cornea. The retina is the eye's inner layer responsible for sensing images and sending signals to the brain through the optic nerve.
The retina turns light into electric signals by the rod and cone cells in the eye. Rods and cones convert light into neural impulses received by the optic nerves. The optic nerves are connected to the brain and are responsible for transmitting neural impulses to the brain.
Once the optic nerves receive the signals, they go through the central ganglia in the brain. The signals go through the visual cortex, the brain's primary area of processing and interpreting visual information.
One of our cerebral cortex's four lobes, the occipital lobe, is devoted to visual processing. This area contains a significant portion of the visual cortex, where interpretation of visual information happens. The whole visual perception process also uses two other lobes of the cerebral cortex: the parietal and temporal lobes. While most raw visual data processing occurs in the occipital lobe, the parietal lobe helps with recognition and the temporal lobe with memory and association.
Visual Perception Disorders
Vision dominates all our senses, and we rely on it more than the others. Visual perception disorders involve difficulties with the interpretation and processing of visual information. This is not the same as problems with vision. Visual processing problems alter how the brain makes sense of information received through the eyes.
Noticing differences. Visual processing problems pose a roadblock in comparing shapes, numbers and symbols, colors, and pictures. One example is in activities involving distinguishing between colors.
Sequencing images. This ability is vital in arranging images, numbers, letters or words in order and distinguishing the correct sequence. One example is in answering math problems.
Coordinating movements. The use of sight to coordinate with body movements. An example is drawing images or copying information from a chart or graph.
Remembering visual material. Long-term memory involves retrieving visual information received a long time ago, such as the appearance of a building from many years ago. Short-term memory includes recent memory such as the face of a person you've just met or specific directions received minutes ago.
Injury to certain parts of the cerebral cortex (e.g. occipital lobe) that play a specialized function in vision causes visual perception disorders such as visual agnosia.
Visual agnosia is a disorder involving difficulties recognizing people and objects, even with good memory and intellectual function. Agnosia does not always make it difficult to recognize all visual inputs; some examples of inputs it affects include objects, colors, faces, and environmental sceneries, leaving others unaffected.
Importance of Visual Perception
Visual perception is vital for humans and animals to interpret and respond to visual information correctly. Some examples of visual perception in daily life include:
- Operating machinery, such as vehicles
- Writing and reading
- Avoiding danger outdoors
- Completing most motor tasks (walking, running, preparing a meal, washing, etc.)
The ability to interpret visual features in the immediate environment makes humans and animals capable of survival and advancement through different life stages.
How Does Visual Perception Work in Psychology?
There are many interpretations of how people perceive visual information in psychology. Since perceptual experiences can be quite different, many experts debate how much visual interpretations rely solely on information sensed in the environment. There are two main types of processing, according to scientists and psychologists:
Bottom-up Approach
In psychology, this is defined as perception based on the data received. Visual information passes through the eyes, and all organs work together to bring in signals towards the brain for the visual cortex to interpret. The brain pieces all the information together as sensory input comes in.
You're walking down a busy street, and a billboard catches your eye, detecting the billboard ad's colors, shapes, and text. Your brain combines all that information, and you perceive a hamburger from a popular fast-food chain.
Top-down Approach
This is another form of visual processing where information is taken within its full context. The top-down approach involves the interpretation of sensory information from what it already knows (e.g., previous experiences) and expects to see (e.g., assumptions).
A person can interpret a blurry picture that seems familiar by picking out familiar shapes. Many visual perception tests and optical illusions are the basis of this approach. This processing technique perceives information based on previous knowledge, making it vulnerable to optical illusions.
Two Main Theories of Visual Perception
Both approaches are based on the theories presented by two experts: Richard Gregory and James Gibson.
Top-Down Processing by Richard Gregory (1970)
Richard Gregory is a psychologist who theorized that perception is a constant process of hypothesis testing. According to the theorist, the ability to interpret vision relies on previous "schemas" or former experiences.
Gregory explains that most of the visual components our body's sensory faculties can gather are lost 90 percent of the time. Only a fraction reaches the brain for processing. Practical evidence supporting the top-down processing theory includes optical illusions, where people have different perceptions even with relatively similar visual skills.
The spinning ballerina is one of the most well-known visual perception activities, where people would argue whether the figure is spinning clockwise or counterclockwise. The differences in perception are a hallmark of hypothesis testing by individuals with various schemas or former experiences.
Bottom-Up Processing Theory by James Gibson (1972)
According to another theorist, James Gibson, sensory processes are deeply tied with visual perceptual skills. Perception is an evolutionary feature of humans that does not need constant hypothesis testing to make sense of visual data. Gibson argued that bottom-up processing is necessary for people's survival, even without prior knowledge of what is being perceived. Essentially, he believed that "what one sees is what one gets" or that sensory information is directly perceived as it is.
Neither theory can explain the full extent of visual perception, leading some experts to believe that the process involves the perceptual cycle where top-down and bottom-up processing interact, as presented by Neisser (1976).
Fg. 3 Optical illusion in a desert, pexels.com
Visual Perception - Key takeaways
- Visual perception is the ability to interpret visual stimuli to make sense of the world.
- Visual information is received by the eye's cornea, lens, and retina. From the retina, rod and cone cells convert light into neural signals, sending it to the brain for interpretation.
- There are two main theories regarding visual perception: Bottom-Up Processing and Top-Down Processing.
- Top-Down Processing (Gregory, 1970) proposes that perception is the process of constant hypothesis testing in the brain to make sense of visual data. All perception is based on former knowledge of visual information.
- Bottom-Up Processing (Gibson, 1972) explains that sensory experiences are perception, meaning that any information received is interpreted quickly to give an appropriate response.
- The Perceptual Cycle involves Top-Down Processing and Bottom-Up Processing interacting with each other.
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