Myers’ EXPLORING PSYCHOLOGY (4th Ed) Chapter 4 Sensation and Perception James A. McCubbin, PhD Clemson University Worth Publishers

Sensation Sensation a process by which our sensory receptors and nervous system receive and represent stimulus energy Perception a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

Sensation Bottom-Up Processing Top-Down Processing analysis that begins with the sense receptors and works up to the brain’s integration of sensory information Top-Down Processing information processing guided by higher-level mental processes as when we construct perceptions drawing on our experience and expectations

Sensation- Basic Principles Psychophysics study of the relationship between physical characteristics of stimuli and our psychological experience of them Absolute Threshold minimum stimulation needed to detect a particular stimulus usually defined as the stimulus needed for detection 50% of the time

Sensation- Thresholds Subliminal below one’s absolute threshold for conscious awareness Difference Threshold the minimum difference that a person can detect between two stimuli 50 percent of the time we experience the difference threshold as a just noticeable difference (jnd)

Sensation- Thresholds 25 50 75 100 Low Absolute threshold Medium Intensity of stimulus Percentage of correct detections Subliminal stimuli When stimuli are detectable less than 50% of the time (below one’s absolute threshold) they are “subliminal”

Sensation- Thresholds Weber’s Law for a difference to be perceived, two stimuli must differ by a constant minimum percentage Sensory adaptation diminished sensitivity as a consequence of constant stimulation

Vision Wavelength Hue Intensity the distance from the peak of one wave to the peak of the next Hue dimension of color determined by wavelength of light Intensity amount of energy in a wave determined by amplitude

Vision Accommodation Retina the process by which the eye’s lens changes shape to focus the image of objects on the retina Retina the light sensitive inner surface of eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information

Vision Rods Cones retinal receptors that detect black, white, and gray necessary for peripheral and twilight vision Cones receptor cells that are concentrated near the center of retina function in daylight or well-lit conditions detect fine detail and give rise to color sensation

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, creating a “blind spot” because there are no receptor cells located there

Vision- Receptors Receptors in the Human Eye Cones Rods Number Location in retina Sensitivity in dim light Color sensitive? Yes Low Center 6 million No High Periphery 120 million

Visual Information Processing Feature Detectors nerve cells in the brain that respond to specific features of the stimulus shape angle movement Stimulus Cell’s responses

Visual Information Processing Parallel Processing processing several aspects of a problem simultaneously the brain’s natural mode of information processing for many functions, including vision

Visual Information Processing 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 cones bipolar cells ganglion cells Recognition: Brain matches the constructed image with stored images Scene

Visual Information Processing Young-Helmholtz Trichromatic (three color) Theory the retina contains three different retinal color receptors- one most sensitive to red, one to green, and one to blue- which when stimulated in combination can produce the perception of any color

The Three Primary Colors of Light

Color-Deficient Vision People who suffer red-green blindness have trouble perceiving the number within the design

Visual Information Processing Opponent-Process Theory theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision some cells stimulated by green and inhibited by red others stimulated by red and inhibited by green Color Constancy perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

Opponent Process- Afterimage Effect

Audition Visual Capture- tendency for vision to dominate the other senses 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

Audition- The Ear Middle Ear the chamber between the eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window

Audition- The Ear Inner Ear Cochlea innermost part of ear, containing the cochlea, semicircular canals and vestibular sacs Cochlea coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses

Touch Skin Sensations pressure warmth cold pain only skin sensation with identifiable receptors warmth cold pain

Pain Gate-Control Theory theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain “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

Taste Taste Sensations Sensory Interaction sweet sour salty bitter the principle that one sense may influence another as when the smell of food influences its taste

Body Position and Movement Kinesthesis the system for sensing the position and movement of individual body parts Vestibular Sense the sense of body movement and position, including the sense of balance

Perception Gestalt an organized whole tendency to integrate pieces of information into meaningful wholes

Perceptual Organization Figure and Ground organization of the visual field into objects (figures) that stand out from their surroundings (ground)

Perceptual Organization- Gestalt Grouping the perceptual tendency to organize stimuli into coherent groups Grouping Principles proximity- group nearby figures together similarity- group figures that are similar continuity- perceive continuous patterns closure- fill in gaps connectedness- spots, lines and areas are seen as unit when connected

Perceptual Organization- Gestalt Proximity Similarity Continuity Closure Connectedness

Perceptual Organization- Gestalt Groupings Gestalt grouping principles are at work here.

Perceptual Organization-Depth Perception ability to see objects in three dimensions allows us to judge distance Binocular cues- depend on use of two eyes retinal disparity images from the two eyes differ closer the object, the larger the disparity convergence neuromuscular cue two eyes move inward for near objects

Perceptual Organization-Depth Perception Monocular Cues-available to either eye alone relative size smaller image is more distant interposition closer object blocks distant object relative clarity hazy object seen as more distant texture coarse --> close fine --> distant

Perceptual Organization-Depth Perception Visual Cliff

Perceptual Organization-Depth Perception Relative Size

Perceptual Organization-Depth Perception Interposition

Perceptual Organization-Depth Perception Monocular Cues (continued) relative height higher objects seen as more distant relative motion closer objects seem to move faster linear perspective parallel lines converge with distance relative brightness closer objects appear brighter

Perceptual Organization-Depth Perception Perspective Techniques

Perceptual Constancy Perceptual Constancy perceiving objects as unchanging despite changes in retinal image color shape size

Perceptual Organization

Perceptual Organization-Muller-Lyer Illusion

Perceptual Organization- Size-Distance Relationship

Perceptual Organization-Brightness Contrast

Perceptual Interpretation Perceptual Adaptation (vision) ability to adjust to an artificially displaced visual field prism glasses Perceptual Set a mental predisposition to perceive one thing and not another

Perceptual Set- Schemas What you see in the center is influenced by perceptual set

Perceptual Set- Schemas Flying Saucers or Clouds?

Perception without Sensation? Extrasensory Perception controversial claim that perception can occur apart from sensory input telepathy clairvoyance precognition Parapsychology the study of paranormal phenomena ESP psychokinesis