Lecture: Sensation and Perception 1/8/16
Lecture: Sensation and Perception 1/8/16 APSY.UE.0002
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This 5 page Class Notes was uploaded by Brianda Hickey on Monday February 8, 2016. The Class Notes belongs to APSY.UE.0002 at NYU School of Medicine taught by Adina Schick, in Spring 2016. Since its upload, it has received 24 views. For similar materials see INTRODUCTION TO PSYCHOLOGY AND ITS PRINCIPLES in Psychlogy at NYU School of Medicine.
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Date Created: 02/08/16
Lecture: Sensation & Perception Sensation and perception are distinct processes: Sensation refers to the process by which our sensory receptors and nervous system receive and represent stimuli from our environment Perception refers to the process of organizing and interpreting sensory information In our every day experiences, sensation and perception blend into one continuous process Experiences of the world depend on: Sensation - Physical stimuli we encounter Perception - Active processing of stimuli inputs Light The stimulus input is light There needs to be light energy in order for one to see ex. When we see a red ﬂower, what strikes our eye is particles of electromagnetic energy that we see as red The Eye Light enters the eye through the cornea Light is bent The light then passes through the pupil to a lens that focuses incoming light rays into an image on the retina The Iris is the colored ring of muscles around the pupil which constricts or dilates depending on the amount of light present in the environment depending on if it is constricting or dilating, it will change the size of the pupil The size of the pupil restricts the amount of light let in dilates = more light goes in Constrict = less light goes in Near sightedness and farsightedness are caused by problems at the lens, it is not bending light correctly Nearsightedness close objects are clearly seen, but distant object sappedart to be blurry the focus of light for distant objects are not quite reaching the retina, making the object appear blurry Farsightedness distant objects are seen clearly, but close objects are clearly seen The distance of light falls behind the retina, it’s over projected The Retina neural tissue lining the inside back surface of the eye Absorbs light, processes images, and sends visual information to the brain Light make its way through the retina’s outer layer of cells to its receptor cells: Rods and Cones Is taking the light energy and turning it into something meaningful for us Rods Detect black, white and gray;necessary for peripheral, twilight vision, night vision Much more receptive in dim light Cones Function in daylight or in well-lit conditions; detect ﬁne detail and give rise to color sensations Without, will not be able to distinguish between diﬀerent colors Do not work well in dim light, that’s why it is diﬃcult to see colors in dim lighting The vision process: 1. Light makes its way to the receptor cells 2. Light energy triggers chemical charges that park neural signals 3. Impulses are sent along the optic nerve 4. The optic nerve carries the information to the brain 5. The thalamus is ready to distribute the information The optic nerve is capable of sending close to a million messages at ones - allows us to see objects in the way that it does Visual input arrives at the visual cortex (in the occipital nerve) In the temporal nerve (next to right ear) contains the feature detecter that allows us to detect faces Viewing the World in Color Tomatoes are every color BUT red, they reﬂect long wavelengths of red. They reﬂect it because they do not contain the color. Color resides in our brains, not in objects ex. we dream in color. If color was linked to objects, then we would not be able to see color in our dreams. The average person can discriminate more than a million diﬀerent color variations Color deﬁcient [blind]:inability to see some or all colors Young-Helmholtz Trichromatic Theory [The Three Color Theory] The retina has three types of color receptors, each especially sensitive to tones of red, green, and blue When we stimulate combinations of the three colors, we are able to see other colors ex. we are able to see yellow by mixing red and green People who are color blind/ deﬁcient, is not that they cannot see color…its that they lack one of the tone sensitive cones problem: Why is it that those who are color deﬁcient able to see the color yellow? [a combination of color] Opponent-Process Theory: Opposing retinal process (red-green, yellow-blue, white-black) enable color vision ex. How the sets work together: Some cells are simulated by red, but inhibited by green [vice versa]. What modern research says: There are two stages of color processing The retina’s use of the red and green cones to gain the information The signals are processed by the opposing retinal cells Perception: Gestalt When given a cluster of sensations, people tend to organize them into a gestalt, an organized whole Our brain does more than just registering information about the world We are constantly ﬁlter sensory information and infer perceptions that make sense to us Gestalt Principles: rules governing how we perceive objects as wholes within their overall context help to explain why we see much of our world as consisting of uniﬁed ﬁgures or forms rather than confusing jumbles of lines and curves One of the principles [Most Important]: Figure and Ground We organize a stimulus into a ﬁgure [focal point] seen against a ground [background], or into objects that stand out from their surroundings The same stimulus can trigger more than one perception Once we discriminate ﬁgure from ground, we need to organize the ﬁgure into a meaningful form Additional Gestalt Principles: Rules are evident [active], even in infants Proximity: nearby objects are grouped together 6 circles forming a triangle: Instead of seeing the circles as a whole, you see a triangle…then 6 circles Similarity: similar ﬁgures are grouped together rectangles and circles forming an image, the rectangles form a cross sign and the circles form boxes Continuity: perceive smooth, continuous objects - seeing something continuously Our processing ﬁlls in the gaps Simplicity: elements are organized in the simplest way possible A triangle, square and circle put together…will not see a shape, or complex shape…will see a circle, square, and a triangle [simple]. Closure: Gaps are ﬁlled to create a complete, whole object - outlining the shape [ not continuous ] Depth Perception Seeing objects in three-dimension enables us to estimate their distance from us ex. If you look out a window, able to estimate the height of a house Gibson & Walk: Visual cliﬀ experiemtns Would a toddler (at the rim of the grand canyon) stop at the edge and not fall over? Used a visual cliﬀ in lab setting: a table and a ﬂoor several feet below, both covered by checkered cloth. A clear glass surface extends from he table out to the ﬂoor (creating the appearance of a sudden drop). Infants are then hesitant to crawl over the glass elevated several feet about ﬂoor. Babies avoid going over the cliﬀ, perceive the depth Use checkered pattern (black & white, red & white) to make the depth more clear to babies switch color to test if the color is the problem Newborn babies vs. newborn animals new born infants, when tested, have a lot of experience (learning) Newborn animals with no experience are able to perceive depth. Each species, by the time they’re mobil are able to perceive depth Depth perception comes with experience with environment, as we get older we become more capable of perceiving depth To perceive depth we use two sets of cues: Binocular cues and Monocular cues Binocular Cues Depth cues that depend on the use of both eyes Because our eyes are 2 1/2 inches apart, each retina recipes a slightly diﬀerent image of the world When our brain compares the two images (left and right retina), our brain computes distance retinal disparity: left and right eyes transmit quite diﬀerent information for near objects but see distant objects similarity the greater the diﬀerence between the two images = the closer the objects ex. hold your ﬁnger close to your nose and take turns blinking each eye, the closer to your nose, the more your ﬁnger will appear to be moving The retinal disparity provide an important cue about the relative distance of objects Monocular Cues Depth cues available to either eye These cues include: relative size: if two objects are similar in size, most people perceive the object that casts the smaller shadow as father away If you see two cars, will assume what is smaller in size as farther away interposition If one object blocks another object, the object must be closer ex. any apartment building that blocks another apartment building, must be closer to you Light and Shadow If you know two objects are exactly the same, the dimmer one is farther away Perceptual Constancy We perceive objects as unchanging (size, shape, color etc) even as retinal images change When we see someone walking away and they get smaller and smaller, they do not seem to be shrinking from existing We perceive objects as having a constant size, even if they are far away At times, however, perceptions are based on inaccurate assumptions, and visual illusions can result Not born with this, hard for a young child to understand that cars outside of an airplane window are not matchbox cars, but cars that can carry many people ex. Muller-Lyer Illusion Westerners are far more susceptible to illusions than others. In western society, things in our environment are much more deﬁned by lines Highlights: our human perception of the world are highly subjective. There are a lot of aspects of our experience that help us form our reality