What is one of the first things you notice about someone? Perhaps it's their hair, smile, or even their eyes. The eyes play an important role, not only in vision but also in social and emotional connection. The eyes have even been called "the window to the soul" as they are a key part of human interaction and connection.
- What is vision?
- How do we see?
- How is the visual information processed?
- How do we use our visual perceptions to create an entire scene?
Definition of Vision in Psychology
Our eyes can receive an excessive amount of energy and process images and light in a fraction of a second. How does vision work? Why can we see color? How do we know how far something is when we look at it? The following text will provide some answers.
Fg. 1 An eye up close, wikicommons.com
Stimulus Input
Our eyes can take light energy and turn them into neural images for our brain to compute. When you look at, for example, a bright yellow ball, your eyes capture pulses of electromagnetic energy into your eyes, and your brain says, "that ball is yellow". There are two characteristics of light that allow us to see colors; wavelength and intensity.
Did you know that butterflies can't perceive the color red as we humans can? Instead, they see ultraviolet light!
Light Energy
A wavelength is the distance from one wave peak to the next. These peaks in the wavelength determine the hue of a color that we are perceiving.
Wavelengths have their amount of energy, which influences the intensity of the color.
How does the eye take light wavelengths to create a color? What areas of the eye does all this work?
Process of Vision in Psychology
The eye has many working components to process colors; the pupil, iris, lens, and retina. Light goes through the pupil like a tunnel. Around this tunnel, or pupil, is the iris which changes and controls the size of the pupil. The iris is in charge of how much light is being let into the pupil. Behind the pupil, is the lens of the eye that focuses on the incoming light and transfers messages or images to the retina.
Fg. 2 The eye, pixabay.com
The retina is not responsible for creating the images that we perceive. It takes light particles, creates neural impulses, and sends them to the brain. The retina does not "see" the images, but instead, the brain deciphers the messages.
The Retina
So, how does the retina pass these messages to the brain? If we looked at one light particle into the eye, we would travel to the rods and cones. Here, the light energy triggers chemicals that spark neural signals and talk to the bipolar cell close by. The bipolar cells will then talk to the nearby ganglion cells that form the eye's optic nerve. The optic nerve then sends the message to our brain, where the thalamus is ready to receive the message.
Visual Information Processing
After your retina processes the message, the light particles pass through it and send the information to the optic nerve; the message is received in the thalamus. But then what happens? The information processed in the thalamus is sent to the occipital lobe in the visual cortex portion of the brain.
Feature Detection
Feature detection cells are important in understanding the features of a scene (lines, edges, angles). When patterns are more complex, these feature detection cells pass information to other brain cortical areas, and supercell clusters become responsive. An example of this would be recognizing a person's face and its elements (freckles, eye color, etc.). Face and object recognition both happen in different areas of the brain.
Brain activity is so specific that brain scans show if a person is looking at a shoe, a table, or a face, based on their brain activity pattern.
Parallel Processing
Your brain can process many features at once in a process called parallel processing. It can divide the scene into subdimensions in a visual scene and simultaneously use these dimensions. Your brain can take the information sent from your retinas, send it to different brain areas, and then create an entire scene into one piece in milliseconds.
Color Vision
How is it possible that we can look at the sky and all agree that it is blue? Light itself is not full of colors - there are light pulses in wavelengths. After much research, Hermann von Helmholtz realized that the brain uses three primary colors (first proposed by physicist Thomas Young), red, green, and blue. This became the Young-Helmholtz trichromatic (three-color) theory, which explains that the retina has three color receptors (sensitive to the colors red, green, and blue). When wavelengths stimulate these color receptors, they can produce an array of color combinations. Later, another theory was proposed for understanding the processing of colors.
Fg. 3 Primary colors, pixabay.com
The opponent-process theory agrees that there are three different color receptors in the retina. However, the colors they perceive are different. Instead, these receptor sets receive red-green, white-black, and yellow-blue. Within the brain and retina, some receptors are turned on by red and turned off by green. The colors can travel as messages in different tunnels of our retina and into the thalamus in a way that can distinguish colors.
Visual Organization
How does our mind form a whole scene from many pieces of information? Through their research, psychologists in Germany realized that people organize these sensations, such as a vision, and create a whole scene. This is the birth of Gestalt theory.
Form Perception
Firstly, our vision follows figure-ground, which means that our vision organizes our visual field by noticing the figures that stand out from the ground. Once our vision has established which figures stand out from the ground, we can bring order to what we are looking at. This is called grouping, the perceptual ability to organize stimuli into groups. Gestalt theorists were able to identify three examples of how we can group stimuli.
Continuity - we perceive smooth images that are not discontinued.
Proximity - we can group figures that are nearby each other.
Closure - we can fill in gaps automatically to create a complete image.
Depth Perception
Our vision can tell us how far an object is from us because of our depth Perception. Depth perception allows us to estimate how far a car is from us or how close the cafe is to where we are walking. But how are we able to understand and perceive depth?
Monocular and binocular cues allow us to understand the depth of objects in our field of vision. When our vision is estimating the distance of an object close, this is considered a binocular cue (using both eyes for measurement). When both eyes are used, there are two sets of images that our brain can compare to make a whole picture. This is because our eyes are placed closely together, and they measure with both retinas. If the object is much further away, both eyes cannot make the judgment correctly. Monocular cues (the use of one eye) gauge the distance.
Motion Perception
Motion Perception is based significantly on the assumptions of the brain. Your brain assumes that if an image or object is getting smaller, it must be retreating, and things that are getting larger are coming toward you. Also, if the object is large, our brains will say that the image is moving slower when that may not be the case. For example, if you look into the sky and notice an airplane, you may think that it is moving incredibly slowly when in fact, it moves at very high speeds.
Perceptual Constancy
Next, we can ask, "How do we make these organized images have meaning?" Perceptual constancy is the ability to recognize images as unchanging based on color, shape, and size. Our brain categorizes objects by color and brightness as well as shape and size.
Color and Brightness & Shape and Size
Color constancy allows for the perception of familiar objects with consistent colors, such as a green apple. If we see a green apple inside a blue grocery bag, the illumination of the color would not be considered consistent. If we see the same green apple alone on a plate, we will recognize the familiar color green of the apple. Shape and size can also affect our perception of images or objects. For example, our bedroom door looks the same as it always has. The shape and size will seemingly change as it opens, although this is not the case. This is called shape constancy.
Vision - Key takeaways
- There are two characteristics of light that allow us to see colors; wavelength and intensity.
There are many working components of the eye involved in processing colors; the pupil, iris, lens, and retina.
Our brain can divide the scene into subdimensions in a visual scene and use each of these dimensions simultaneously.
Our vision follows figure-ground, which means that our vision organizes our visual field by noticing the figures that stand out from the ground.
Depth perception allows us to estimate how far a car is from us or how close the cafe is from where we are walking.
Explanations 
Textbooks 
Exams 
Magazine 
