PSY Week 6 Part 2 Senses and Perception
PSY Week 6 Part 2 Senses and Perception PSY 151
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This 6 page Class Notes was uploaded by merlec16 on Tuesday October 4, 2016. The Class Notes belongs to PSY 151 at Wake Forest University taught by Ashley L. Heffner in Fall 2016. Since its upload, it has received 3 views.
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Date Created: 10/04/16
PSY Perception and the Senses Vision and Hearing p. 224-230, 247-265 How Does the Eye Work? Sight, smell, taste, touch, and hearing Researchers do not agree on a precise definition of the term sense Six primary areas: eyes, nose, tongue, ears, skin, and non-skeletal interior of the body The Eye Receives Light Eye has one function and one function only: o To received light and process the images that result Electromagnetic radiation- energy that travels around the world in waves of variable intensity (amplitude) that are separated by varying lengths known as wavelengths Wavelengths- a measure of the lengths between electromagnetic waves Visible light exists only in a very narrow spectrum of electromagnetic wavelengths Amplitude- intensity of a sound of light output source expressed in the height of light of sound waves Eyes Form Images of the World, but Do Not “See” Cornea- transparent membrane comprised of nerve fibers that covers the eyes In order for images to form, light reflected from an object must first pass through cornea Light is refracted as it passes through cornea so that it may be gathered more efficiently Pupil- a small opening in the iris of the eye Light passes through pupil Iris- muscular structure of the eye around the pupil that expands and contracts to regulate the amount of light entering the eye o If available light is low the iris expands (dilates) if light is strong it contracts Light then conveyed to other transparent structure the lens Lens- flattens or thickens to help focus light upon the retina Vitreous humor- gel-like substance through which light must pass through before arriving at the retina o Fills 80% of the volume of the eye Retina- light-sensitive membrane spread out across most of the inner surface of the rear of the eye o Upon the retina that images are formed When light finally reaches retina the images are upside down and left/right reversed Seeing still has not yet occurred Not until the images are transduced to electrical signals and these signal reach the brain that the process of seeing (visual perception) actually begins Rods and Cones Retina contains 125 million photoreceptors Photoreceptors- neurons dedicated to capturing light in order to initiate transduction o Two primary types: rods and cones Rods- specialized to allow night vision and vision in low light o Dark adaptation period- 30 minutes for rods to fully adapt Cones- specialized for day vision, color vision, and capturing fine detail o Peak sensitivities are to light wavelengths associated with human color vision o Fovea- small region near the center of the retina that contains the greatest concentration of cones and thus provides the clearest images and sharpest focus o Images seem less sharply focused on the farther away from the fovea they get Contains virtually no rods Visual Signals Are Interpreted in the Visual Cortex Optic nerve- nerve that carries neural signals from the back of the retina to the CNS Optic disc- no rods or cones “blind” o Area where optic nerve leaves the retina Blind spot- the brain “fills in” this missing information o Area formed by optic disc that contains no rods or cones Information passes through thalamus Signals are relayed to the visual cortex Visual cortex- area of the brain that interprets visual neural signals o Much of the information is conveyed by optic nerve is interpreted and perceived as visual image of the world o Also sensations of touch relayed from hands and fingers are interpreted as visual images Brains – Not Objects – Have Color Color is not a physical property of an object Color results from an interaction between light and brains Color is a psychological property Trichromacy: How Colors Are Combines in the Mind’s Palette Additive color mixture- primary colors were combined at various intensities and in various combinations Subtractive color mixture- when new colors are formed by mixing pigmented substances such as paints (different than additive color mixture) Trichromatic theory of color vision- describes how all colors are created through the additive mixture of blue, green, and red o Short, medium, and long cones in the retina are sensitive to respective wavelengths (correspond to blue, green, and red) S-, M-, and L-cones allow us to distinguish between light at different wavelengths, and to perceive different colors as a result of the additive mixture of these wavelengths Red-green color deficiency- when M- and L-cones are equally sensitive to red and green, making differentiation of these colors impossible Opponent Process Theory Opponent process theory- proposes that because certain wavelengths of light cannot be combined in an additive process, colors are created in color vision by mixing in three opposing pairs: blue vs. yellow, red vs. green, and black vs. white When a color is a mixture of the basic opponent process colors one of the dimension of each opponent neurons is firing, and the other is suppressed How Do We Perceive Visual Images? During man’s evolution only available light source was the sun Illumination came from above and out eyes are primarily adapted to interpret visual imagery based on the “assumption” that light is coming from above When you shine a flashlight under someone’s chin, your perceptual “machinery” is attempting to impose order on stimuli it did not evolve to interpret Visual Images Are Organized Brain “fills in” the identity of each word and places it correctly in the context of a thought Gestalt school- early school of psychology that emphasized the mechanisms by which human beings create perceptions of meaningful “wholes” from inherently fragmented and meaningless sensory signals The whole is greater than the sum of its parts Figure and Ground Figure- aspect of a visual image upon which a person focuses, while regulating other aspects of the image to the background Ground- term for those aspects of a visual image relegated to the background Ground shapes are “accidental” outcomes of how figures are arranges Gestalt Perceptual Grouping Important original laws of perceptual grouping: o Proximity- people tend to group figures together that are near one another o Similarity- people tend to group figures together if they are similar to one another o Closure- if there is a gap in the image of a familiar object, people will mentally fill in the missing elements o Good continuation- any visual elements which suggest a continued line will be grouped together Visual Images Have Depth Depth perception- visual perception mechanism that allows for judgement of distance of objects and creates a “3-D” image even though retinal images are “2-D” Visual cliff experiment suggests very early development of depth perception in humans Depth Perception Relies Upon Two Types of Cues Binocular cues- necessitate both eyes – specifically retinal disparity and convergence 1. Retinal disparity- based on the fact that each eye takes in a slightly different, but overlapping, view 2. Convergence- based on the fact that ocular muscles rotate eyes inward when viewing close objects “cross-eyed” Monocular cues- can operate even when only one eye is available specifically relative size, texture gradient, linear perspective, interposition, atmospheric influence, and position on the horizon 1. Relative size- when an object is closer their image on the retina is larger than when they are more distant Ames room 2. Linear perspective- any parallel lines moving away from an observer converge as they stretch out into the distance until they eventually meet at a single point, known as the vanishing point 3. Interposition- (object blocking) when one object blocks the view of another object, we assume that the blocked object is behind the first object and therefore farther away from us 4. Position on the horizon- Objects viewed below the horizon line are perceived as closer Objects viewed above the horizon, the lower they are in the visual field and the and the farther away they appear Moon illusion- when moon is low it looks larger Visual Images Have Constancy Perceptual constancy- ability to perceive an object as itself regardless of changes in angle or viewing, distance, or illumination o Size constancy- allows us to perceive an object as the same size regardless of the size of its image on our retina o Shape constancy- allows us to perceive an object as the same shape regardless of the angle from which we view it o Brightness constancy- allows us to perceive n object as the same brightness regardless of the available illumination o Color constancy- allows us to perceive an object as the same color regardless of the amount of type of illumination How Do Evolution, Culture, and Experience Affect Perception? Biological motion- evidence that human beings possess specific visual, neural, and cognitive tools “dedicated” to recognizing and distinguishing faces, and those specialized for detecting movement in living creatures Face Recognition: Specialized Tool of Perception? Ability to distinguish faces from other objects or body parts and to recognize specific familiar faces o Infants as young as 3 days old prefer to look at faces and patterns depicting faces than non-face patterns o People are better able to recognize an image of an upside-down object than an upside-down face o Damage to specific brain regions results in an inability to recognize objects or words, but may leave facial recognition processes intact Fusiform face area- (FFA) “blueberry sizes” cortical region of the right hemisphere seemingly set aside exclusively for face perception and recognition Middle face patch- The Importance of Experience in Perception Evolutionary origin of face perception mechanisms would not necessarily mean that these mechanisms are innate Researchers argue that experience is critical for the development of specialized visual-cognitive mechanisms such as face perception Face perception is an experience-expectant process At birth face perception mechanisms are only a potential Perception is Influenced by Expectation and Attention Experience profoundly influences people’s perception Expectation is particularly influential Change blindness- inability to detect changes in a scene following a brief distraction Attention or inattention can prevent us from seeing the objects and personas at all Inattentional blindness- inability to see highly visible objects a which one is looking directly when attention is drawn elsewhere Perceptual Set Perceptual set- the expectations, biases, and preconceptions that we bring to a given perception People From Different Cultures May “See Things Differently” Muller-Lyer illusion- a visual illusion where two lines of identical length appear to be of unequal length Japanese showed greater tendency to view objects embedded in their background and context, rather than isolating the object and focusing on its unique properties Americans fixed gaze upon the focal object sooner and remained longer than the Chinese Far easterners focus holistically on the relationship of objects in context when perceptually organizing the environment Westerners focus analytically on the specific qualities of objects in order to categorize and organize them May reflect differences in social orientation
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