Have you ever wondered why one person sees images in a painting differently from another person, or how an individual can appreciate the nuances of a musical piece when another person cannot tell the differences in horns being played? This slight variance in how one person perceives the same sensory information differently from another is perception. Specifically, perception is the organization, identification, and interpretation of sensory stimuli (information) produced by neuronal signals within the brain so that an individual can understand the surrounding environment. The sensory organs will receive the stimulus, such as light or sound, and transmit that information to the brain where it is interpreted. However, perception of the sensory information is modulated in the brain by a person’s ability to learn, previous memories, expectations, and how attentive the person was at the time of the stimulus. Because perception is a very integrated process, this is why eyewitnesses to a car accident may not remember specific details the same way.
Perception has two processes for integrating sensory information. The first is processing initial low-level sensory stimuli into higher-level information that the brain understands or can identify. An example is seeing a ball and identifying its shape (large, round) and color (orange), or object recognition. The second step in perception processing is connecting the person’s expectation (knowledge) and concepts with sensory stimuli. This is influenced by how attentive the person is at the time during the first part of perception processing. Continuing the example, the brain will process the use of the ball and the complex goals of the games associated with the ball. Here the goal of a large orange ball is to be bounced, passed, and shot through a high basket to score two or three points. This additional information (complex rules and strategy for playing basketball) is instantly linked to the object. As a person has more experience with a basketball, his or her understanding and perception will be different from that of someone just learning.
Sensory stimuli, whether it is light, sound, and so on, is not always persistent and is often incomplete or rapidly changing. The brain, however, helps us to feel that our external environment is stable by modulating the sensory information when it is received. For some types of sensory information the brain has developed sensory maps, which connect external stimuli to specific locations across the surface of the brain. These maps are also interconnected and often will influence each other.
The visual system is a sensory system that is responsible for the sense of sight or vision. Visual perception, however, consists of the psychological process of how an animal or person sees a visual image. Thus, visual perception takes the information from visual processing and attempts to “make sense” of the object. Additionally, visual perception is important for the perception of movement, the perception of depth, and perception of color. These three types of visual perception are based in Gestalt psychology, which tries to understand how the human eye sees objects first as a whole and then as a sum of its individual parts. It also looks at how the entire object is anticipated even when the parts are not integrated, such as filling in the “blind spots” of the visual field to complete the entire image.
Perception of Movement
To perceive movement, the neurons located in region V5 are activated when the speed and direction of an object are seen. In humans, the vestibular system is also necessary for understanding motion perception. This is because it compares the speed of the person against the speed of the object to determine the motion.
Perception of Depth
Seeing the world in three dimensions (3D) and seeing how far an object is from a person is called depth perception. This perception is best with binocular vision as well as utilizing depth cues such as stereopsis (viewing a 3D scene with both eyes), parallax (looking at an object along two different lines of sight and measuring it against the angle made by the two lines), and convergence of the eyes (looking toward the center or “crossing your eyes”).
As light hits an object, the color an individual perceives is actually the color of light being reflected by the object’s surface. Ratios of S-, M-, and L-cones located in the retina are activated based on the amount and wavelengths of light that enter the eye. As more cones are activated, the eye is able to differentiate more hues and vibrancy of a color. Additionally, color perception requires visual experience so that the brain can interpret what the person is seeing. This is called visual-experience-dependent neural plasticity.
Jennifer L. Hellier
See also: Color Perception; Visual Perception
Bear, Mark F., Barry W. Connors, & Michael A. Paradiso. (2007). Neuroscience exploring the brain (3rd ed.). Baltimore, MD: Lippincott Williams & Wilkins.
Kandel, Eric R., James H. Schwartz, Thomas M. Jessell, Steven A. Siegelbaum, & A. J. Hudspeth (Eds.). (2012). Principles of neural science (5th ed.). New York, NY: McGraw-Hill.