Sensation and Perception Dr. Dennis C. Sweeney 2/18/2009 Sensation.ppt 1 What We Will Cover in This Section Overview Psychophysics Sensations Hearing Vision Touch Taste Smell Kinesthetic Perception 2/18/2009 Sensation.ppt 2 Sensation The stimulation of a sensory receptor and the transmission of sensor information to the central nervous system. 2/18/2009 Sensation.ppt 3 1
Sensory Adaptation Process by which sensory cells lose their power to respond after a period of unchanged stimulation. 2/18/2009 Sensation.ppt 4 2/18/2009 Sensation.ppt 5 Perception How we interpret the information our senses receive. 2/18/2009 Sensation.ppt 6 2
Gestalt Psychology We integrate the individual sensations into something meaningful. 2/18/2009 Sensation.ppt 7 How We Acquire This Interpretation Some characteristics are inborn. Some characteristics are acquired through experience. 2/18/2009 Sensation.ppt 8 Characteristics of Perception Categories We group sensations into categories based on their features. Relational The pattern of the stimulus has to be related in some way for it to make sense. 2/18/2009 Sensation.ppt 9 3
Selective Attention Focusing awareness on a subset of available stimuli. We are not aware of everything that is going on in the environment. 2/18/2009 Sensation.ppt 10 2/18/2009 Sensation.ppt 11 Characteristics of Perception Adaptive Helps us survive. Automatic. 2/18/2009 Sensation.ppt 12 4
Psychophysics: What is it? The study of the correspondence between physical stimulation and psychological experience. How loud should a siren be before we can hear it over traffic noise? How strong should an odor be in natural gas before we can detect it? 2/18/2009 Sensation.ppt 13 Absolute Threshold The amount of stimulation necessary for the stimulus to be detected. The stimulus strength at which a signal (stimulus) is detected half of the time. 2/18/2009 Sensation.ppt 14 Examples of Absolute Threshold Sense Light Sound Taste Smell Touch Detection Threshold A candle flame at 30 miles on a dark, clear night. Tick of a mechanical watch at 20 feet. One teaspoon of sugar in 2 gallons of water. One drop of perfume in a three bedroom apartment. The wing of a bee falling on your cheek from one centimeter. 2/18/2009 Sensation.ppt 15 5
Difference Threshold The smallest amount by which a stimulus can be changed and the difference (change) be detected half the time. 2/18/2009 Sensation.ppt 16 Just Noticeable Difference (JND) The smallest difference between two sensations that allows them to be sensed as being different. 2/18/2009 Sensation.ppt 17 Signal Detection Theory Our perceptual judgment is a combination of the sensation and our decision-making processes. 2/18/2009 Sensation.ppt 18 6
Human Sensing Systems 2/18/2009 Sensation.ppt 19 Vision 2/18/2009 Sensation.ppt 20 2/18/2009 Sensation.ppt 21 7
Visual Processes Rods Receptors that are located in the edges of the retina that are most active in dim light. They do not produce the sensation of color. Cones Receptors in the central part of the retina that are most active during normal light. They produce the sensation of color. Dark adaptation The improvement of the eye s sensitivity when going from light to darkness. 2/18/2009 Sensation.ppt 22 Color Vision 2/18/2009 Sensation.ppt 23 2/18/2009 Sensation.ppt 24 8
2/18/2009 Sensation.ppt 25 Color Vision Trichromatic Theory There are three specialized receptors (red, green, blue) to code color. Opponent Process Theory There are three systems each specializes in a pair of colors (opponents) red-green, blue-yellow, black-white. 2/18/2009 Sensation.ppt 26 Visual Perception 2/18/2009 Sensation.ppt 27 9
Characteristics of Visual Perception Physical Structure Light and dark Figure and ground Depth Inferences Since we see only parts of an object we must infer the whole from the parts. 2/18/2009 Sensation.ppt 28 Form Perception: Figure Ground Figure The object that is distinguished from the background. Ground Backdrop or background areas against which figures stand out. 2/18/2009 Sensation.ppt 29 Form Perception: Grouping Proximity Objects closer together are perceived as being one unit. Similarity Similar objects are perceived as being one unit. 2/18/2009 Sensation.ppt 30 10
Proximity 2/18/2009 Sensation.ppt 31 Similarity 2/18/2009 Sensation.ppt 32 Form Perception: Grouping Closure We perceive incomplete figures as being complete. Common Fate Elements moving in the same direction at the same rate are grouped together. 2/18/2009 Sensation.ppt 33 11
Common Fate 2/18/2009 Sensation.ppt 34 Motion Perception Induced Motion Illusion where a stationary object appears to move and the moving frame of reference appears to be stationary. Apparent Motion Illusion in which one or more stationary lights flickering in succession are perceived as a single moving light. 2/18/2009 Sensation.ppt 35 Depth Perception 2/18/2009 Sensation.ppt 36 12
Monocular Cues to Distance When we use only one eye, these are the cues we use to tell us approximately how far away something is. 2/18/2009 Sensation.ppt 37 Texture Gradient 2/18/2009 Sensation.ppt 38 Pictorial Cues: Interposition 2/18/2009 Sensation.ppt 39 13
Pictorial Cues: Linear Perspective 2/18/2009 Sensation.ppt 40 Pictorial Cues: Relative Size 2/18/2009 Sensation.ppt 41 Binocular Distance Cues Retinal disparity. The horizontal differences of the image in the two eyes. Convergence. The degree to which the eyes turn inward to fixate on an object. 2/18/2009 Sensation.ppt 42 14
Convergence 2/18/2009 Sensation.ppt 43 Visual Constancies Size Constancy The ability to perceive the true size of an object despite variations in the size of its retinal image. Shape constancy The ability to perceive the true shape of an object despite variations in the orientation in the retinal image. 2/18/2009 Sensation.ppt 44 Hearing (Audition) Pitch(Frequency) The sensation of highness or lowness, depends on the frequency of the sound wave. Loudness (Amplitude) The volume of the sound; depends on the amplitude of the sound wave. 2/18/2009 Sensation.ppt 45 15
Hearing Timbre The distinguishing quality of a complex sound. 2/18/2009 Sensation.ppt 46 2/18/2009 Sensation.ppt 47 2/18/2009 Sensation.ppt 48 16
2/18/2009 Sensation.ppt 49 Auditory Perception Figure and Ground Proximity Continuity Similarity Closure Detecting a voice in crowded room. Notes close together in a melody form the phrases. Following the melody on one instrument while another is playing a different tune. Similar voices are perceived as being in one group. Understanding a person even when there is cell phone interference. 2/18/2009 Sensation.ppt 50 Taste 1. Sweet 2. Sour 3. Salt 4. Bitter 5. Umami 2/18/2009 Sensation.ppt 51 17
Smell (Olfaction) Olfactory bulb. The center where odor-sensitive receptors send their signals in the brain. Pheremones Chemical signals used to send scent signals to other members of the same species. 2/18/2009 Sensation.ppt 52 2/18/2009 Sensation.ppt 53 Vestibular & Kinesthetic Vestibular Sense of how your body body is oriented. Kinesthetic Sense of how your body parts are positioned and movement of body parts. 2/18/2009 Sensation.ppt 54 18
Touch Skin senses that register sensations of Pressure (touch). Warmth. Cold. Pain. 2/18/2009 Sensation.ppt 55 Pain The body s response to stimuli that are intense enough to cause tissue damage. Gate Control Theory Certain cells in the spinal cord act as gates to interrupt and block some pain signals while sending others to the brain. 2/18/2009 Sensation.ppt 56 Gate Control Theory of Pain Pain experience depends on whether pain impulses get past a nerve gate in the spinal cord. The brain controls this gate. When we focus on the pain we feel it. When we focus on other things the pain recedes. Phantom Pain 2/18/2009 Sensation.ppt 57 19
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