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Chapter 3 Sensation and Perception Ms. Chauvin I. Sensation 1. Sensation-the process by which the sensory receptor gives rise to 2. History—earliest psychological research on sensation examined relationship between Psychophysics—study of the correlation between physical stimuli and the behavior or mental experience the stimuli invoked (oldest field within psychology) Gustav Fechner— 3. Absolute Threshold— Psychologists measure absolute threshold by recording Trying to see a dim light in a dark room, hearing a soft sound in a quiet room, etc If you’ve ever had a hearing test 4. Sensory Adaptation—diminishing responsiveness of sensory systems to prolonged sensory output Sunshine feels Hum of A/C 5. Signal Detection Theory— Can have life or death consequences—wartime sentry vs. peacetime sentry fall asleep 6. Difference Threshold— Test—use pairs of stimuli—ask observer whether two stimuli are the same or different 7. Just Noticeable Difference (JND)— Ernest Weber—Developed Weber’s Law: For the avg. person to perceive their differences, 8. Sensory Physiology: Transduction—conversion of one form of energy like light, to another form, such as neural impulses 9. Vision—your eyes’ ability to respond to light Mechanisms: 6 major parts: Color Blindness—some cones sensitive to _________________, others to _________________, others to ____________________________. When one type of cones is missing or deficient ________________________________results. More common in _______________; thought to be ________________________ passed on to _________________by __________________. Pathways to Brain: destination of much visual information is the part of the _____________________known as the _________________________________ 1) 2) ganglion cells register 3) cortical neurons called ____________________________respond to particular features of the scene such as __________________, ______________________, ________________________, ______________________. From this, the brain assembles the image. 4) The visual cortex passes this info. on to the Color Vision—two theories of color vision 1) Young-Helmholtz 3-Color Theory: the retina has 3 types of color receptors, each sensitive to one of three colors: . Our perception of color is due to the 2) Opponent-Process Theory (Hering)—There are opposing retinal processes (cones which enable color vision. Cells stimulated by one would be inhibited by another. Confirmed by Color Constancy—perceiving familiar objects as having consistent color, even though changing illuminations alter wavelengths alter Color will remain roughly constant ****we see color thanks to our brain’s 10. Audition (hearing)—sound wave travels at a rate of 1100 ft/sec. It has two basic properties: Frequency: Amplitude: 3 Dimensions of Sound: pitch, loudness and timbre 1) pitch: 2) loudness: physical intensity; determined by its______________. (sound waves with large amplitude are experienced as ______________and those with small amplitude as _______________) Loudness is measured in _____________________. See thermometer of familiar sounds. Prolonged exposure to sounds louder than ______________________________can produce permanent hearing loss. 2) Timbre—reflects the components of a sound’s complex sound wave. Timber sets apart Mechanisms of the auditory system 1) outer ear channels 2) middle ear transmits vibrations through 3 tiny bones ( ) to a snail-shaped tube in inner ear (cochlea) 3) inner ear’s (cochlea) membrane 4) basilar membrane bends hair cells; 5) neural messages sent to Deafness—two types 1) conduction deafness— 2) nerve deafness— Two Theories of Pitch Perception—ability to distinguish the chirp of a bird from the roar of a truck 1) Place Theory—Hermann von Helmholtz— 2)Frequency Theory—theory that nerve impulses traveling up to the auditory nerve match the ***frequency theory best explains how we perceive_______________________, place theory best explains ______________________, volley theory best explains ________________________. Location—humans use sound to determine the locations of objects in space through the use of 2 mechanisms: 1) relative timing— 2) relative intensity— 11. Olfaction (Smell)—in humans, evolved mainly as a mechanism for _________________________; in some species, ______________________________________. Classifications: Mechanism: 1)odors react with receptor proteins on the 2) nerve impulses are initiated and convey 3) smell is a lesser sense in humans, but humans do, like animals, emit pheromones ****smell is the ONLY sense that is NOT routed through the thalamus; for that reason, it is more tied to emotional memory than any other sense 12. Taste— Taste receptors –surface of tongue covered with 1) four primary taste qualities: 2) 3) taste receptors get replaced, but 13. Touch—hidden beneath the skin are __________________________________. When they are stimulated, they send messages to the brain. What commonly is called touch is actually three different receptors: Pressure receptors—found over different parts of the body in differing amounts. ( Pain receptors: respond to a # of intense stimuli cutting or pricking, twisting, heat or cold, damage to tissue or pressure (vary in # from 50 per sq. cm on bottom of foot to 230 in same sized space on neck) 1)pain is body’s response to noxious stimuli— 2)starting at spinal cord— 3)psychology of pain—your emotional responses, context factors, and your interpretation of the situation can be as important as the actual physical stimuli in determining how much pain you experience ***pain can be modified by 4) Gate-Control Theory of Pain—Ronald Melzack— suggests that cells in the spinal cord act as ***it is the message descending from the brain that provides the psychological context in which you experience pain One aspect of cutaneous sensitivity plays a central role in _______________________________. Through touch, you communicate your desire to 1) Erogenous Zones— 14. Vestibular & Kinesthetic Senses Vestibular— (tiny hairs and canals in inner ear inform you how your head is moving when you turn, nod, or tilt it) Kinesthetic— Notifies the brain of your position and movement of body parts II. Perception— Bottom-up processing—recognition of an object by breaking it down to its component parts; relies heavily on sensory receptors Top-down processing— 1. Selective Attention— 2. Perceptual Illusions—reveal ways that we normally organize and interpret our sensations Muller-Lyer Illusion— 3. Perceptual Organization-Gestalt—emphasis on our tendency to 4. Form Perception—a “top down” process, according to Gestalt Figure-ground— Grouping—our minds follow certain rules for grouping stimuli together 1) Proximity— 2) Similarity— 3) Continuity— 4) Connectedness— 5) Closure— 5. Depth Perception—seeing things in 3D enables us to estimate their distance from us Visual Cliff—Gibson and Walk— Binocular Cues—rely on both eyes’ images 1) retinal disparity— 2) convergence— Monocular Cues—those we need only one eye to see 1)interposition— 2) relative size-3) relative clarity— 4) texture gradient— 5) relative height— 6) relative motion (motion parallax)— 7) linear perspective— 8) light and shadow— ***artists use monocular cues to convey depth on a flat canvas; so do people with sight in only one eye 6. Motion Perception—brain computes motion partly based on 7. Perceptual Constancy—we now that a stimulus remains the same even though it does not appear to (airplane on ground vs. in air) PERCEPTUAL INTERPRETATION—perceptual abilities both nature AND nurture 8. Sensory Deprivation and Restored Vision—cat experiments—there seems to be a ________________________for normal sensory and perceptual development 9. Perceptual Adaptation-10. Perceptual Set—our experiences assumptions, and expectations greatly influence what we perceive; 11. Extrasensory Perception (ESP)—claim that perception can exist apart from sensory input; includes telepathy, clairvoyance, and precognition parapsychology— telepathy— clairvoyance— precognition— ESP has yet to be scientifically validated Testing ESP--