Sensation and Perception

Sensation and Perception
Sensation & Perception 4/30/2019 Sensation and Perception Prepared by Krista D. Forrest, Ph.D., and Michael Lee These slides © 2004 Pearson Education Canada Inc., Toronto, Ontario. Chapter 6 ©1999 Prentice Hall

Our Sensational Senses
Sensation & Perception 4/30/2019 Our Sensational Senses Defining sensation and perception The riddle of separate senses Measuring the senses Sensory adaptation Sensory overload ©1999 Prentice Hall

Defining Sensation and Perception
Sensation & Perception 4/30/2019 Defining Sensation and Perception Sensation The detection of physical energy emitted or reflected by physical objects. It occurs when energy in the external environment or the body stimulates receptors in the sense organs. Perception The process by which the brain organizes and interprets sensory information. ©1999 Prentice Hall

Sensation & Perception
4/30/2019 Ambiguous Figure Colored surface can be either the outside front surface or the inside back surface Cannot simultaneously be both Brain can interpret the ambiguous cues two different ways ©1999 Prentice Hall

The Riddle of Separate Sensations
Sensation & Perception 4/30/2019 The Riddle of Separate Sensations Sense receptors Specialized cells that convert physical energy in the environment or the body to electrical energy that can be transmitted as nerve impulses to the brain. ©1999 Prentice Hall

Sensation & Perception Processes
4/30/2019 Sensation & Perception Processes Figure 3.Davis 2 from: Kassin, S. (1998). Psychology, second edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

Doctrine of Specific Nerve Energies
Sensation & Perception 4/30/2019 Doctrine of Specific Nerve Energies Different sensory modalities exist because signals received by the sense organs stimulate different nerve pathways leading to different areas of the brain. Synthesia A condition in which stimulation of one sense also evokes another. ©1999 Prentice Hall

Absolute Sensory Thresholds
Sensation & Perception 4/30/2019 Absolute Sensory Thresholds Vision: A single candle flame from 30 miles on a dark, clear night Hearing: The tick of a watch from 20 feet in total quiet Smell: 1 drop of perfume in a 6-room apartment Touch: The wing of a bee on your cheek, dropped from 1 cm Taste: 1 tsp. Sugar in 2 gal. water ©1999 Prentice Hall

4/30/2019 Difference Threshold The smallest difference in stimulation that can be reliably detected by an observer when two stimuli are compared; Also called Just Noticeable Difference (JND). ©1999 Prentice Hall

Signal-Detection Theory
Sensation & Perception 4/30/2019 Signal-Detection Theory A psychophysical theory that divides the detection of a sensory signal into a sensory process and a decision process. Stimulus is Present Absent Response: “Present” Hit False Alarm Response: “Absent” Miss Correct Rejection ©1999 Prentice Hall

Sensory Adaptation and Deprivation
Sensation & Perception 4/30/2019 Sensory Adaptation and Deprivation Adaptation The reduction or disappearance of sensory responsiveness when stimulation is unchanging or repetitious. Prevents us from having to continuously respond to unimportant information. Deprivation The absence of normal levels of sensory stimulation. ©1999 Prentice Hall

4/30/2019 Sensory Overload Overstimulation of the senses. Can use selective attention to reduce sensory overload. Selective attention The focusing of attention on selected aspects of the environment and the blocking out of others. ©1999 Prentice Hall

4/30/2019 What We See Hue Visual experience specified by colour names and related to the wavelength of light. Brightness Lightness and luminance; the visual experience related to the amount of light emitted from or reflected by an object. Saturation Vividness or purity of colour; the visual experience related to the complexity of light waves. ©1999 Prentice Hall

4/30/2019 An Eye on the World Cornea Protects eye and bends light toward lens. Lens Focuses on objects by changing shape. Iris Controls amount of light that gets into eye. Pupil Widens or dilates to let in more light. ©1999 Prentice Hall

4/30/2019 An Eye on the World Retina Neural tissue lining the back of the eyeball’s interior, which contains the receptors for vision. Rods Visual receptors that respond to dim light. Cones Visual receptors involved in colour vision. Most humans have 3 types of cones. ©1999 Prentice Hall

The Structures of the Retina
Sensation & Perception 4/30/2019 The Structures of the Retina ©1999 Prentice Hall

Why the Visual System is not a Camera
Sensation & Perception 4/30/2019 Why the Visual System is not a Camera Much visual processing is done in the brain. Some cortical cells respond to lines in specific orientations (e.g. horizontal). Other cells in the cortex respond to other shapes (e.g., bulls-eyes, spirals, faces). Feature-detectors Cells in the visual cortex that are sensitive to specific features of the environment. ©1999 Prentice Hall

Hubel & Wiesel’s Experiment
Sensation & Perception 4/30/2019 Hubel & Wiesel’s Experiment ©1999 Prentice Hall

4/30/2019 How We See Colours Trichromatic theory Opponent process theory Figure 5.04 from Wade, C., & Tavris, C. (2002). Invitation to Psychology, 2nd Ed. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

4/30/2019 Trichromatic Theory Young (1802) & von Helmholtz (1852) both proposed that the eye detects 3 primary colours: red, blue, & green All other colours can be derived by combining these three. Figure 3.9 from: Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

Opponent-Process Theory
Sensation & Perception 4/30/2019 Opponent-Process Theory A competing theory of colour vision, which assumes that the visual system treats pairs of colours as opposing or antagonistic. Opponent-Process cells are inhibited by a colour, and have a burst of activity when it is removed. ©1999 Prentice Hall

Test of Colour Deficiency
Sensation & Perception 4/30/2019 Test of Colour Deficiency Figure 3.12 from: Kassin, S. (1998). Psychology, second edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

Constructing the Visual World
Sensation & Perception 4/30/2019 Constructing the Visual World Form perception Depth and distance perception Visual constancies: When seeing is believing Visual illusions: When seeing is misleading ©1999 Prentice Hall

4/30/2019 Figure and Ground Proximity Seeing 3 pair of lines in A. Similarity Seeing columns of orange and red dots in B. Continuity Seeing lines that connect 1 to 2 and 3 to 4 in C. Closure Seeing a horse in D. Figure 3.23 from: Kassin, S. (1998). Psychology, second edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

Depth and Distance Perception
Sensation & Perception 4/30/2019 Depth and Distance Perception Binocular Cues: Visual cues to depth or distance that require the use of both eyes. Convergence: Turning inward of the eyes, which occurs when they focus on a nearby object. Retinal Disparity: The slight difference in lateral separation between two objects as seen by the left eye and the right eye. ©1999 Prentice Hall

Depth and Distance Perception
Sensation & Perception 4/30/2019 Depth and Distance Perception Monocular Cues: Visual cues to depth or distance that can be used by one eye alone. ©1999 Prentice Hall

4/30/2019 The Ames Room A specially-built room that makes people seem to change size as they move around in it The room is not a rectangle, as viewers assume it is A single peephole prevents using binocular depth cues Figure 3.24 from: Kassin, S. (1998). Psychology, second edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

4/30/2019 Visual Constancies The accurate perception of objects as stable or unchanged despite changes in the sensory patterns they produce. Shape constancy Location constancy Size constancy Brightness constancy Colour constancy ©1999 Prentice Hall

4/30/2019 Shape Constancy Even though these images cast shadows of different shapes, we still see the quarter as round Figure 3.25 from: Kassin, S. (1998). Psychology, second edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

4/30/2019 Visual Illusions Illusions are valuable in understanding perception because they are systematic errors. Illusions provide hints about perceptual strategies. In the Muller-Lyer illusion (above) we tend to perceive the line on the right as slightly longer than the one on the left. Figure 5.07 from Wade, C., & Tavris, C. (2002). Invitation to Psychology, 2nd Ed. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

4/30/2019 The Ponzo Illusion Linear perspective provides context Side lines seem to converge Top line seems farther away But the retinal images of the red lines are equal! Figure 3.3Davis 2 from: Kassin, S. (1998). Psychology, second edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

4/30/2019 Fooling the Eye The cats in (a) are the same size The diagonal lines in (b) are parallel You can create a “floating fingertip frankfurter” by holding hands as shown, 5-10” in front of face. ©1999 Prentice Hall

4/30/2019 What We Hear Loudness The dimension of auditory experience related to the intensity of a pressure wave. Pitch The dimension of auditory experience related to the frequency of a pressure wave. Timbre (pronounced “TAM-bur”) The distinguishing quality of sound; the dimension of auditory experience related to the complexity of the pressure wave. ©1999 Prentice Hall

Auditory Localization
Sensation & Perception 4/30/2019 Auditory Localization Sounds from different directions are not identical as they arrive at left and right ears Loudness Timing Phase The brain calculates a sound’s location by using these differences. Figure 3.14 from: Kassin, S. (1998). Psychology, second edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

Taste: Savoury Sensations
Sensation & Perception 4/30/2019 Taste: Savoury Sensations Papillae Knoblike elevations on the tongue, containing the taste buds (Singular: papilla). Taste buds Nests of taste-receptor cells. ©1999 Prentice Hall

4/30/2019 Taste Buds Photograph of tongue surface (top), magnified 75 times. 10,000 taste buds line the tongue and mouth. Taste receptors are down inside the “bud” Children have more taste buds than adults. Figure 3.17 from: Kassin, S. (1998). Psychology, second edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

Smell: The Sense of Scents
Sensation & Perception 4/30/2019 Smell: The Sense of Scents Airborne chemical molecules enter the nose and circulate through the nasal cavity. Vapors can also enter through the mouth and pass into nasal cavity. Receptors on the roof of the nasal cavity detect these molecules. ©1999 Prentice Hall

Gate-Control Theory of Pain
Sensation & Perception 4/30/2019 Gate-Control Theory of Pain Experience of pain depends (in part) on whether the pain impulse gets past neurological “gate” in the spinal cord and thus reaches the brain. ©1999 Prentice Hall

Neuromatrix Theory of Pain
Sensation & Perception 4/30/2019 Neuromatrix Theory of Pain Theory that the matrix of neurons in the brain is capable of generating pain (and other sensations) in the absence of signals from sensory nerves. ©1999 Prentice Hall

The Environment Within
Sensation & Perception 4/30/2019 The Environment Within Kinesthesis The sense of body position and movement of body parts; also called kinesthesia. Equilibrium The sense of balance. Semicircular Canals Sense organs in the inner ear, which contribute to equilibrium by responding to rotation of the head. ©1999 Prentice Hall

Perceptual Powers: Origins and Influences
Sensation & Perception 4/30/2019 Perceptual Powers: Origins and Influences Inborn abilities Critical periods Psychological and cultural Influences on perception ©1999 Prentice Hall

4/30/2019 The Visual Cliff Glass surface, with checkerboard underneath at different heights Visual illusion of a cliff Baby can’t fall Mom stands across the gap Babies show increased attention over deep side at age 2 months, but aren’t afraid until about the age they can crawl (Gibson & Walk, 1960) Figure 3.27 from: Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

4/30/2019 Critical Periods If infants miss out on experiences during a crucial period of time, perception will be impaired. When adults who have been blind since birth have vision restored, they may not see well Other senses such has hearing may be influenced similarly. ©1999 Prentice Hall

Psychological and Cultural Influences on Perception
Sensation & Perception 4/30/2019 Psychological and Cultural Influences on Perception We are more likely to perceive something when we need it. What we believe can affect what we perceive. Emotions, such as fear, can influence perceptions of sensory information. Expectations based on our previous experiences influence how we perceive the world. Perceptual Set A habitual way of perceiving, based on expectations. All are influenced by our culture. ©1999 Prentice Hall

4/30/2019 Perceptual Set What you see in the centre figures depends on the order in which you look at the figures: If you scan from the left, see an old woman If you scan from the right, see a woman’s figure Figure 3.28 from: Kassin, S. (1998). Psychology, second edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

4/30/2019 Context Effects The same physical stimulus can be interpreted differently We use other cues in the situation to resolve ambiguities Is this the letter B or the number 13? Figure 3.Davis 29 from: Kassin, S. (1998). Psychology, second edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

Subliminal Perception
Sensation & Perception 4/30/2019 Subliminal Perception Perceiving without awareness visual stimuli can affect your behaviour even when you are unaware that you saw it nonconscious processing also occurs in memory, thinking, and decision making these effects are often small, however, and difficult to demonstrate and work best with simple stimuli ©1999 Prentice Hall

Subliminal Perception
Sensation & Perception 4/30/2019 Subliminal Perception Perception versus Persuasion there is no empirical research to support popular notions that subliminal persuasion has any effect on a person’s behaviour persuasion works best when messages, in the form of advertising or self-help tapes, are presented above-threshold, or at a supraliminal level ©1999 Prentice Hall

Extrasensory Perception
Sensation & Perception 4/30/2019 Extrasensory Perception Extrasensory Perception (ESP): The ability to perceive something without ordinary sensory information This has not been scientifically demonstrated Three types of ESP: Telepathy – Mind-to-mind communication Clairvoyance – Perception of remote events Precognition – Ability to see future events ©1999 Prentice Hall

4/30/2019 Parapsychology The study of purported psychic phenomena such as ESP and mental telepathy. Persinger suggests that psychic phenomena are related to signs of temporal lobe epilepsy in otherwise neurologically normal individuals. Most ESP studies produce negative findings and are not easily replicated. ©1999 Prentice Hall

4/30/2019 Parapsychology J. B. Rhine conducted many experiments on ESP using stimuli such as these. Rhine believed that his evidence supported the existence of ESP, but his findings were flawed. Figure 3.33 from: Kassin, S. (1998). Psychology, second edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

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