Fifth Week PSY 2012
Fifth Week PSY 2012 Psy 2012
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This 5 page Class Notes was uploaded by Lindsay Everest on Sunday December 27, 2015. The Class Notes belongs to Psy 2012 at University of South Florida taught by Jennifer Bosson in Fall 2015. Since its upload, it has received 12 views. For similar materials see Introduction to Psychology in Psychlogy at University of South Florida.
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Date Created: 12/27/15
PSY 2012 Bosson Introduction to Psychology Chapter Four Notes: “Sensation and Perception” Section One: The Process: Sensation Perception I. Core Activities A. SENSATION: stimulation of sensory organs B. TRANSDUCTION: converts physical energy of sensations into action potential which will be sent to the CNS via sensory receptor cells C. PERCEPTION: the organization, identification, and interpretation of a sensation in order to form a mental representation II. Sensory Systems (The first five senses respond to information outside of the body) A. Vision: color vision, light vision B. Smell C. Taste: salt, sour, bitter, sweet, umami (savory) The first five senses D. Hearing respond to E. Touch: texture, pressure, vibration, temperature information outside F. PROPRIOCEPTION: responds to sensory information of the body from inside the body 1. KINESTHETIC SENSE: body movement and position; receptors in joints and muscles spinal cord thalamus somatosensory cortex and cerebellum 2. VESTIBULAR SENSE: head movement and position (balance); receptors in inner ear thalamus cerebellum, muscles of eye, digestive system 3. Acute Polyneuritis – the nervous system cannot receive information about the body’s position or movement III. PSYCHOPHYSICS: methods that measure strength of a stimulus and the observer’s subjective sensibility to that stimulus A. ABSOLUTE THRESHOLD: the minimal intensity of physical energy needed to just barely detect a stimulus in 50% of the trials 1. Vision sensory system has a greater absolute threshold than any other sensory systems 2. Touch and taste thresholds are limited to direct contact with body B. JUST NOTICEABLE DIFFERENCE (JND): the minimal change in a stimulus that can just barely be detected; the human perceptual system is better at detecting changes in stimulation than the simple onset or offset of stimulation 1. The JND is not a fixed quantity; rather, it depends on how intense the stimuli being measured are and on the particular sense being measured, as well as the standard it is being measured against. 2. WEBER’S LAW: the just noticeable difference of a stimulus is a constant proportion despite variations in intensity IV. SENSORY ADAPTATION: sensitivity to prolonged stimulation tends to decline over time as an organism adapts to current conditions A. Our sensory systems respond more strongly to changes in stimulation than to constant stimulation. A stimulus that doesn’t change usually doesn’t require any action but a change in stimulation often signals a need for action. B. Ex: Your car probably emits a certain hum all the time that you’ve gotten used to. But a change in stimulation often signals a need for action. If your car starts making different noises, you’re not only more likely to notice them, but you’re also more likely to do something about it. Section Two: The Vision Sensory System I. VISUAL ACUITY: the ability to see fine detail; in ophthalmology: the smallest line of letters a typical person can read from 20 feet away A. 20/20 vision – being able to clearly see what you should see 20 feet away B. MYOPIA: nearsightedness, caused by an eyeball that is too long C. HYPEROPIA: farsightedness, caused by an eyeball that is too short II. The Human Eye A. The CORNEA (transparent layer forming the front of the eye) refracts light through the PUPIL (hole in the center of the iris) B. The IRIS (doughnut shaped muscle) dilates or contracts the pupil according to how much light should be let in C. LENS (clear disc) further focuses light through the RETINA (light-sensitive tissue lining the back of the eyeball) 1. ACCOMMODATION: the process by which the eye maintains a clear image on the retina 2. If objects are farther away, muscles flatten the lens. If objects are nearby, muscles make the lens rounder. D. Retina has photoreceptor cells that convert light into action potential via sensory receptor cells during the process of transduction 1. CONES: detect color, operate under normal daylight conditions, and allow us to focus on fine detail; 6 million in the eye 2. RODS: become active under low-light conditions for night vision; 120 million in the eye E. Light reflecting from peripheral objects is less likely to land in the FOVEA (an area on the center of the retina where vision is the clearest because it has the highest concentration of cones; there are no rods at all) making them appear colorless and fuzzy F. Photoreceptor cells form the innermost layer of the retina, beneath a layer of transparent neurons formed from bipolar and retinal ganglion cells 1. Bipolar Cells – collect neural signals from rods and cones and send them to RCGs 2. Retinal Ganglion Cells (RCGs) – organize the signals and send them to the brain via bundled RCG axons which form the optic nerve (a hole in the retina that has no rods or cones) 3. The optic nerve creates a BLIND SPOT: location in the visual field that produces no sensation on the retina. * Color blindness results if cones (that correspond to different wavelengths of light – blue, green, or red) are missing. III. Visual Processing in the Brain A. Action potentials containing information encoded by the retina travel along the optic nerve and enter the brain at the OPTIC CHIASM: point where the optic nerves from each eye cross over each other B. Contralateral processing – half of the axons in the optic nerve that leave each eye come from retinal ganglion cells that code information in the right visual field whereas the other half code information in the left visual field. These two nerve bundles link to the left and right hemisphere respectively. C. The optic nerve travels from each eye to the thalamus. D. Visual signals travel to the back of the brain to AREA V1: part of the occipital lobe that contains the primary visual cortex, specialized for encoding edge orientation (perceiving shape). E. There are two pathways, or visual streams, that project from the occipital cortex to visual areas in other parts of the brain. 1. The VENTRAL STREAM travels into the lower levels of the temporal lobes and includes brain areas that represent an object’s shape and identity, a.k.a. the “what” pathway Agnosia is the inability to process sensory information. Forms of agnosia that are the result of a problem in the ventral stream result in an inability to process visual sensory information. VISUAL-FORM AGNOSIA: inability to recognize objects by sight, often caused by damage to ventral stream PROSOPAGNOSIA: inability to recognize human faces 2. The DORSAL STREAM travels to the parietal lobes (and some of the middle/upper levels of the temporal lobes), connecting with brain areas that identify the location and motion of an object, a.k.a. the “where” pathway F. The proximal stimulus is upside down and backwards to the distal stimulus because light moves in straight lines. By the time the image reaches the occipital lobe, the image is righted and the area V1 is able to produce the retinotopic map. Section Three: Perception I. PERCEPTUAL CONSTANCY: even as aspects of sensory signals change, perception remains consistent A. Size Constancy – adjusts for distance; the brain understands that a person far away is actually the same size as the person close by B. Shape Constancy – stimuli are perceived as changing position rather than shape when manipulated C. Color Constancy – stimuli are perceived as having constant color despite changes in illumination II. Perceptual Grouping Rules A. Rooted in the principle of Gestalt Psychology that we organize parts into a whole automatically B. SIMPLICITY: when confronted with multiple interpretations, the visual system tends to select the simplest or most likely interpretation C. PROXIMITY: objects that are close together tend to be grouped together (e.g., associate lines of similar objects as rows/columns) D. SIMILARITY: regions similar in color, lightness, shape, or texture are perceived as belonging to the same object (e.g., team members have the same uniform) E. CLOSURE: tendency to fill in missing elements of a visual scene, allowing us to perceive edges that are separated by gaps as belonging to complete objects F. CONTINUITY: edges/contours that have the same orientation tend to be grouped together G. COMMON FATE: perceiving elements that are moving in the same direction as being more related than elements that are stationary or that move in different directions H. FIGURE AND GROUND: some visual stimuli stand out (figure) from the rest of the environment (ground); novel, intense, bright, moving, closer, loud, and small objects (e.g., letters on a page) are often seen as figural elements 1. REVERSIBLE FIGURE-GROUND ILLUSION: an image can be viewed two different ways because the figure and ground are equally contrasting 2. CAMOUFLAGE ILLUSION: occurs when the figure and ground cannot be distinguished from one another III. Depth Perception A. Monocular Depth Cues – require one eye, useful for detecting distance of far way objects 1. Relative image size 2. Interposition – a blocking object is closer than a blocked object 3. Linear Perspective – parallel lines seem to converge as they recede into the distance 4. Texture Gradient – the size of elements and the distance between them grows smaller as they recede from the observer (e.g., field of flowers) B. BINOCULAR DISPARITY: the difference in the retinal images of the two eyes that provides information about depth C. Are we born with perception? 1. The visual cliff experiment shows that at least by the time infants can crawl, we can perceive depth. 2. The case study of Kenge showed that humans are born with a predisposition to perceive depth, but require experience with the physical world to develop this ability. IV. Perceptual “Blindness” – perception is active but resources are limited; sometimes we fail to notice [important] elements of a visual field A. CHANGE BLINDNESS: when people fail to detect changes to the visual details of a scene B. INATTENTIONAL BLINDNESS: a failure to perceive objects that are not the focus of attention (e.g., multi-tasking is dangerous because it divides your attention)
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