Understanding Sensation and Perception: A Comprehensive Overview
This chapter explores the intricate processes of sensation and perception, focusing on how we receive and interpret sensory information. It delves into the functioning of the eye, including the roles of rods and cones in visual perception, the structure of the ear in auditory processing, and how our other senses—like touch, taste, and smell—contribute to our overall experience. Concepts such as feature detection, color vision theories, and pain perception are addressed, illustrating the complexities of how our brain organizes and interprets sensory data.
Understanding Sensation and Perception: A Comprehensive Overview
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Presentation Transcript
Sensing & Perceiving Information • Sensation: Receiving • Perception: Organizing & Interpreting
Vision – The Eye • Light enters eye through the cornea • Passes through the pupil and lens • Focused into an image on the retina • Retina • Light sensitive inner surface of the eye • Contains Rods & Cones • Receptor cells convert light to neural impulses and send to brain • Brain reassembles impulses into an image
Vision – Retina Receptors • Rods • detect black, white, and gray • necessary for peripheral and twilight vision • Cones • concentrated near the center of retina • function in daylight or well-lit conditions • detect fine detail • color vision
Receptors in the Human Eye Cones Rods Number 6 million 120 million Location in retina Center Periphery Sensitivity in dim light Low High Color sensitive? Yes No Vision--Receptors
The Eye • Optic Nerve: nerve that carries neural impulses from the eye to the brain • Blind Spot: point at which the optic nerve leaves the eye • No receptor cells • creates a “blind spot”
Vision – Feature Detection • Feature Detectors • nerve cells that respond to specific features of a stimulus • shape, angle, or movement • fMRI can be used to determine what object a person is looking at
Visual Information Processing • Parallel Processing • processing many parts of a problem all at once • the brain’s natural mode of information processing for many functions (including vision)
Abstraction: Brain’s higher-level cells respond to combined information from feature-detector cells Feature detection: Brain’s detector cells respond to elementary features-bars, edges, or gradients of light Retinal processing: Receptor rods and conesbipolar cells ganglion cells Recognition: Brain matches the constructed image with stored images Scene Visual Information Processing
Color-Deficient Vision • People who suffer red-green blindness have trouble perceiving the number within the design
Color Vision • Young-Helmholtz trichromatic (three-color) theory • retina has 3 different color receptors (red, green, blue) • different combinations allow for the perception of any color • Opponent-process theory • opposing processes of retina enable color vision • e.g., some neurons are turned on by red and off by green
Audition • Audition- the sense of hearing • Frequency- the number of complete wavelengths that pass a point in a given time • Pitch- a tone’s highness or lowness • depends on frequency • long sound waves = low frequency & low pitch • short sound waves = high frequency & high pitch
Audition--The Ear • Sound waves • auditory canal eardrum (vibrates with the waves) middle ear cochlea (in inner ear) triggers neural impulses (auditory nerve) thalamus auditory cortex (temporal lobe) • Middle Ear • chamber between the eardrum and cochlea • contains 3 tiny bones (hammer, anvil, stirrup) that transmit vibrations to the cochlea
Audition--The Ear • Inner Ear • innermost part of ear • Contains the Cochlea • a fluid-filled tube through which sound waves trigger nerve impulses
Locating Sounds • sound reaches one ear more intensely and more quickly • auditory system is able to detect tiny differences • hearing loss in one ear = difficulty locating sounds
Touch • Skin Sensations • pressure • only skin sensation with identifiable receptors • warmth • cold • pain • Rubber hand illusion • http://www.youtube.com/watch?v=TCQbygjG0RU
Pain • No theory explains all available findings • Gate-Control Theory (1960s) • provides a useful model for understanding pain • the spinal cord contains small fibers (conduct pain signals) and large fibers (conduct other sensory signals) • “gate” opened by the activity of pain signals traveling up small nerve fibers • “gate” closed by activity in larger fibers or by information coming from the brain
Pain Control • Massaging area next to pain • Distraction • Diverting the brain’s attention may bring relief • Pleasant imagery • Count backward • Virtual reality
Taste • Taste Sensations • sweet • sour • salty • bitter • savory (umami)
Taste • Taste receptors • reproduce themselves every 2 weeks • taste sensitivity and # of taste buds decrease as we age • Sensory Interaction • one sense may influence another sense • the smell of food influences its taste • smell + texture = flavor • rubber hand illusion (vision & touch interact)
Smell • humans can detect 10,000 odors • olfactory receptor cells • respond to aromas • messages sent through receptor axons to the olfactory bulb in the brain • messages then travel from olfactory bulb to temporal lobe & limbic system • odors can evoke memories
Body Position and Movement • Sixth sense • Kinesthesis • the system for sensing the position and movement of individual body parts • interacts with vision • Vestibular sense • monitors head and body position to maintain balance • fluid in the inner ear moves when head moves • messages are sent to the cerebellum
Perceptual Organization- organizing & interpreting info from senses • Gestalt • an organized whole • tendency to integrate pieces of information into meaningful wholes • Necker cube
Perceptual Organization • First: Need to discriminate objects from backgrounds • Figure and Groundperceiving an object (figure) as distinct from its surroundings (ground) • In a busy restaurant: • voice you attend to = figure • all other voices = ground
Perceptual Organization- Gestalt • Next step: Need to organize the figure into a meaningful form • Grouping • the tendency to organize stimuli into meaningful groups • grouping rules identified by Gestalt psychologists • the “whole” that we perceive differs from the sum of its parts
Perceptual Organization- Gestalt • Grouping Rules • proximity - we group nearby figures together • similarity - we group similar figures together • continuity – we perceive continuous patterns • closure – we fill in gaps to create complete objects • connectedness - spots, lines, and areas are seen as a unit when connected
Proximity Similarity Continuity Closure Connectedness Perceptual Organization- Gestalt
Perceptual Organization-Depth Perception Visual Cliff
Perceptual Organization • Depth Perception • seeing objects in three dimensions • allows us to estimate distance • Visual Cliff • laboratory technique used to test depth perception • http://www.youtube.com/watch?v=eyxMq11xWzM
Perceptual OrganizationDepth Perception • Binocular cues – • depth cues • depend on use of two eyes • retinal disparity • images from the two eyes differ • brain compares the images to compute distance • the larger the difference, the closer the object
Perceptual OrganizationDepth Perception • Monocular Cues • depth cues needed for objects at further distances • available to each eye separately • relative height • higher objects seen as more distant • relative size • smaller image is more distant
Depth Perception • Monocular Cues (continued) • interposition • if one object blocks our view of another, we perceive that object to be closer
Depth Perception • Monocular Cues (continued) • relative clarity • hazy object seen as more distant • relative motion • as we move, stable objects appear to also move • fix gaze on object: those beyond appear to move with you; those in front appear to move backward • relative brightness • dimmer objects seem farther away
Depth Perception • Monocular Cues (continued) • linear perspective • parallel lines appear to converge with distance
Perceptual Constancy • perceiving objects as unchanging despite changes in illumination and retinal image • able to recognize objects despite changes in color, shape, & size
Shape Constancy Shape constancy – as a door opens the shape projected on retina looks more like a trapezoid…but we still perceive it as rectangular.
Perceptual Constancy • Color depends on context • Color Constancy • we perceive familiar objects as having consistent color • even if illumination changes and alters the wavelengths reflected by the object
Perceptual Interpretation • Perceptual Adaptation • (vision) ability to adjust to an artificially displaced visual field • glasses that invert view of the world (looks upside down) • humans can adapt relatively quickly and learn to coordinate movements accurately
Perceptual Interpretation • Perceptual Set • a mental predisposition to perceive one thing and not another • our experiences and expectations influence what we perceive
