Chapter 5 Sensation and Perception PDF

Because learning changes everything. ® Chapter 5 Sensation and Perception Copyright 2021 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior writte...

Because learning changes everything. ® Chapter 5 Sensation and Perception Copyright 2021 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  Sensing the World Around Us Sensation: the activation of the sense organs by a source of physical energy. Perception: the sorting out, interpretation, analysis, and integration of stimuli by the sense organs and brain. Stimulus: energy that produces a response in a sense organ. © McGraw Hill LLC 2  Absolute Thresholds: Detecting What’s Out There Absolute threshold: the lowest intensity of a stimulus that an organism can detect. The stimulus intensity that is detected 50% of the time. As defined by psychophysicists, noise is background stimulation that interferes with the perception of other stimuli. © McGraw Hill LLC 3  How Sensitive Are You? Test your awareness of the capabilities of your senses. Which of the following are “True,” and which “False”? 1.On a clear, dark night, you can see a candle flame from a distance of 30 miles. 2.A single drop of perfume can be detected over the area of a 3-room apartment. 3.Under quiet conditions, the ticking of a watch can be heard from 20 feet away. 4.You would need 2 tablespoons of sugar to detect its taste when dissolved in 2 gallons of water. © McGraw Hill LLC Source: Galanter, Eugene. “Contemporary psychophysics.” In New directions in psychology, Edited by R. Brown, E. Galanter, E. Hess, & G. Maroler. New 4  Difference Thresholds: Noticing Distinctions Between Stimuli Difference threshold: the smallest level of added or reduced stimulation required to sense that a change in stimulation has occurred. Also called a just noticeable difference. Weber’s law: a basic law of psychophysics stating that a just noticeable difference is a constant proportion to the intensity of an initial stimulus (rather than a constant amount). © McGraw Hill LLC 5  Perception Perception is a constructive process by which we go beyond the stimuli that are presented to us and attempt to construct a meaningful situation. © McGraw Hill LLC 6  Top-Down and Bottom-Up Processing Perception involves both top-down and bottom-up processing Top-down processing: perception is guided by higher-level knowledge, experience, expectations, and motivations. Bottom-up processing: perception that consists of the progression of recognizing and processing information from individual components of a stimuli and moving to the perception of the whole. © McGraw Hill LLC 7  Top-down vs. bottom-up 8 © McGraw Hill LLC 8  Top-down processing Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. © McGraw Hill LLC 99  Top-down processing The power of context is shown in this figure. Note how the B and the 13 are identical. © McGraw Hill LLC Source: Coren, S., Ward, L. M. (19 89). Sensation and perception (3rd ed.). San Diego, C A: Harcourt Brace Jovanovich. 10  Sensation vs. Perception Sensation ~ Physical Perception ~ Psychological © McGraw Hill LLC 11 11  Sensory Adaptation Adaptation: an adjustment in sensory capacity after prolonged exposure to unchanging stimuli. The decline in sensitivity to sensory stimuli is due to the inability of the sensory nerve receptors to fire off messages to the brain indefinitely. Sensory nerve receptor cells are most responsive to changes in stimulation. Constant stimulation is not effective in producing a sustained reaction. © McGraw Hill LLC 12  FACTORS AFFECTING PERCEPTION 1. Sensory Adaptation 2. Attention - Inattentional blindness - Failure to notice something that is completely visible because of a lack of attention. - Video © McGraw Hill LLC 13  FACTORS AFFECTING PERCEPTION 3. Motivation - Sometimes we think we hear something such as a phone ringing when it is not because we are motivated to perceive it (such as waiting for an important phone call). - Signal detection theory – change in stimulus detection as a function of current mental state. 4. Beliefs, values, prejudices and expectations - People who hold positive attitudes towards low-fat foods are more likely to rate foods with low-fat labels as tasting better than people with less positive attitudes about low-fat products. © McGraw Hill LLC 14  Factors affecting perception 15 5. Life/Cultural experiences - One study found that people from Western cultures (where there is a perceptual context of buildings with straight lines) were more likely to experience certain types of visual illusions, like the Muller-Lyer illusion, than individuals from non-western cultures (where they are more likely to live in round huts). © McGraw Hill LLC 15  MODULE 11 FIGURE 6 In the Müller-Lyer illusion (a), the vertical line on the left appears shorter than the one on the right, even though they are identical in length. One explanation for the Müller-Lyer illusion suggests that the line on the left (with arrow points directed outward) is perceived as the relatively close corner of a rectangular object, such as the building corner in (b), and the line on the right (with the arrow points directed inward) is interpreted as the inside corner of a rectangular object, such as the room extending away from us (c). Our previous experience with distance cues leads us to assume that the outside corner is closer than the inside corner and, consequently, the inside corner must be longer. © McGraw Hill LLC 16  Perceptual Illusions: The Deceptions of Perceptions Visual illusions: physical stimuli that consistently produce errors in perception. Most explanations for visual illusions concentrate on either the physical operation of the eye or our misinterpretation of the visual stimulus. Cultural expectations play a role. © McGraw Hill LLC 17  MODULE 11 FIGURE 5 In building the Parthenon, the Greeks constructed an architectural wonder that looks perfectly straight, with right angles at every corner. (b) However, if it had been built with completely true right angles, it would have looked as it does here. (c) To compensate for this illusion, the Parthenon was designed to have a slight upward curvature, as shown here. © McGraw Hill LLC (a) Mlenny Photography/E+/Getty Images; (b and c) Luckiesh, M. (1921). Scientific American Monthly, 3, 497–501. 18  MODULE 11 FIGURE 7 The “devil’s tuning fork” has three prongs… or does it have two? © McGraw Hill LLC 19  Perception and Culture © McGraw Hill LLC 20 20  Light and Sound Waves © McGraw Hill LLC 21 21  Vision Vision starts with light, the physical energy that stimulates the eye. Light is a form of electromagnetic radiation waves. Light is measured in wavelengths, the distance between peaks of the light waves. The visual spectrum is the range of wavelengths that is visible to the human eye. Your eyes convert light to a form used by neurons, serving as messengers to the brain. © McGraw Hill LLC 22  MODULE 9 FIGURE 1 The visible spectrum—the range of wavelengths to which people are sensitive—is only a small part of the kinds of wavelengths present in our environment. Access the text alternative for slide images. © McGraw Hill LLC 23  MODULE 9 FIGURE 2 Although human vision is far more complicated than the most sophisticated camera, in some ways basic visual processes are analogous to those used in photography. Like the automatic lighting system of a traditional, nondigital camera, the human eye dilates to let in more light and contracts to block out light. Access the text alternative for slide images. © McGraw Hill LLC 24  Illuminating the Structure of the Eye 1 Rays of light first travel through the cornea, a transparent, protective window at the front of the eye. Because of its curvature, the cornea bends—or refracts —light as it passes through. It plays a primary role in focusing the light more sharply. The iris is the colored part of the eye. The pupil is the dark hole in the center of the iris. The pupil’s size depends on the amount of light in the environment. In dim surroundings it opens to allow more light to enter. © McGraw Hill LLC 25  Illuminating the Structure of the Eye 2 Once light passes through the pupil, it enters the lens. The lens acts to bend the rays of light so that they are properly focused on the back of the eye. Accommodation refers to the process by which the lens changes its thickness to focus light. The lens becomes flatter when viewing distant objects and rounder when looking at closer objects. https://www.merckmanuals.com/home/eye-disorders/biology-of-the-eyes/struc ture-and-function-of-the-eyes © McGraw Hill LLC 26  Reaching the Retina 1 Retina: the part of the eye that converts the electromagnetic energy of light to electrical impulses for transmission to the brain. The retina has two kinds of light-sensitive receptor cells: Rods: thin, cylindrical cells that work well in low-light Cones: cone-shaped cells that are responsible for sharp focus and color perception, particularly in bright light. © McGraw Hill LLC 27  Rods and Cones The basic cells of the eye. Light entering the eye travels through the ganglion and bipolar cells and strikes the light-sensitive rods and cones located at the back of the eye. The rods and cones then transmit nerve impulses to the brain via the bipolar and ganglion cells. © McGraw Hill LLC 28  Sending The Message from the Eye to the Brain Optic nerve: a bundle of ganglion axons that carry visual information to the brain. The optic nerve passes through the retina where there are no rods and cones, creating a blind spot. © McGraw Hill LLC 29  Explaining Color Vision Trichromatic theory of color vision: there are 3 kinds of cones in the retina, each of which responds primarily to a specific range of wavelengths. Blue-violet, green, yellow- red. Challenged by the afterimage phenomenon, where colors in the afterimage differ from those in the © McGraw Hill LLC 30  Explaining Color Vision Opponent-process theory of color vision: receptor cells for color are linked in pairs, working in opposition to each other: black- white, yellow- blue, green-red. Figure 5.16 Stare at the white dot for 30–60 seconds and then move your eyes to a blank piece of white paper. What do you see? This is known as a negative afterimage, and it provides empirical support for th opponent-process theory of color vision. https://www.youtube.com/watch? © McGraw Hill LLC 31  Depth Perception: Translating 2-D to 3- D Depth perception: the ability to view the 1 world in three dimensions and to perceive distance. We use a variety of cues in a visual scene to establish our sense of depth. Some of these are binocular cues, which means that they rely on the use of both eyes. Ex: Binocular disparity is the difference in the images seen by the left eye and the right eye. The difference between the images in the two eyes provides us with a way of determining distance. © McGraw Hill LLC 32  Depth Perception: Translating 2-D to 3-D 2 Monocular cues permit humans to obtain a sense of depth and distance with just one eye. EX: Linear perspective: objects in the distance appear to converge. © McGraw Hill LLC 33  Sound Waves Frequency ~ pitch the number of wave cycles that occur in a second. Low frequencies are very low in pitch—the characteristic that makes sound seem “high” or “low.” Amplitude ~ loudness The range of sound we can hear is measured in decibels. © McGraw Hill LLC 34 34  MODULE 10 FIGURE 2 The sound waves produced by different stimuli are transmitted—usually through the air —in different patterns, with lower frequencies indicated by fewer peaks and valleys per second. © McGraw Hill LLC 35  Sensing Sound 1 Sound localization: the process by which we identify the direction from which a sound is coming. Location of the outer ears on different sides of the head helps. Sound: the movement of air molecules brought about by a source of vibration. Eardrum: the part of the ear that vibrates when sound waves hit it. Vibrations are then transferred into the middle ear, which contains three bones—the hammer, anvil, and stirrup—that transmit vibrations to the oval window leading to the inner ear. © McGraw Hill LLC 36  Sensing Sound (2) The inner ear changes the sound vibrations into a form transmittable to the brain. Cochlea: a coiled tube in the ear filled with fluid that vibrates in response to sound. Basilar membrane: a vibrating structure through the center of the cochlea, containing sense receptors for sound. Hair cells: tiny cells covering the basilar membrane that, when bent by vibrations entering the cochlea, transmit neural messages to the brain. © McGraw Hill LLC 37  Ear The major parts of the ear. https://www.nidcd.nih.gov/health/journey-of-sound-video Access the text alternative for slide images. © McGraw Hill LLC 38  Decibels © McGraw Hill LLC 39 39  The Physical Aspects of Sound 3 Place theory of hearing: different areas of basilar membrane respond to different frequencies. Frequency theory of hearing: the entire basilar membrane acts like a microphone, vibrating as a whole in response to a sound. After an auditory message leaves the ear, it is transmitted to the auditory cortex of the brain. Auditory neurons respond to specific types of sounds. Speech perception requires fine discriminations among sounds. Echolocation © McGraw Hill LLC 40  The Physical Aspects of Sound 4 Several structures of the ear are related more to our sense of balance than to our hearing. This vestibular system responds to the pull of gravity and allows us to maintain our balance. Semicircular canals: three tube-like structures of the inner ear containing fluid that sloshes when the head moves, signaling rotational or angular movement to the brain. © McGraw Hill LLC 41  HEARING LOSS Deafness – the partial or complete inability to hear. Congenital deafness – deafness from birth. Conductive hearing loss: - Associated with a failure in the vibration of the eardrum and/or movement of the ossicles. Can be caused by: - Age - Genetic predisposition - Environmental effects – exposure to extreme noise, certain illnesses or damage due to toxins. Sensorineural hearing loss – failure to transmit neural signals from the cochlea to the brain. - Can be caused by Meniere’s disease which results in degeneration of inner ear structures. © McGraw Hill LLC 42  Cochlear Implants 43 https://www.youtube.com/watch?v=QBi1Bij39H8 https://www.youtube.com/watch?v=lfbQbQ- NWB0&t=122s © McGraw Hill LLC 43  Taste The sense of taste (gustation) involves receptor cells that respond to four basic stimulus qualities: sweet, sour, salty, and bitter. A fifth category, umami, involves food stimuli that contain amino acids. The receptor cells are located in roughly 10,000 taste buds. These wear out and are replaced every 10 days or so. “Supertasters” are highly sensitive to taste. “Nontasters” are insensitive to taste. © McGraw Hill LLC 44  Figure 5.21 (a) Taste buds are composed of a number of individual taste receptors cells that transmit information to nerves. (b) This micrograph shows a close-up view of the tongue’s surface. 45 © McGraw Hill LLC 45  Smell The human sense of smell—called olfaction— permits us to detect more than 10,000 separate smells. Smells are strongly linked with memory. The sense of smell is sparked when the molecules of a substance enter the nasal passages and meet olfactory cells, the receptor neurons of the nose. Smell may also act as a hidden means of communication, through the release of pheromones. These chemicals produce a social response in other members of the same species. © McGraw Hill LLC 46  Smell Figure 5.22 Olfactory receptors are the hair-like parts that extend from the olfactory bulb into the mucous membrane of the nasal cavity. © McGraw Hill LLC 47 47  The Skin Senses: Touch, Pressure, Temperature, and Pain 1 Skin senses: the senses of touch, pressure, temperature, and pain. Operate through nerve receptor cells located at various depths throughout the skin. Pain has both physical and psychological components. Susceptibility to pain is different from person to person. When a cell is damaged, it releases a chemical called substance P, which transmits pain messages to the brain. The experience of pain also depends heavily on emotions and thoughts. © McGraw Hill LLC 48  Skin sensitivity Skin sensitivity in various areas of the body. The lower the average threshold is, the more sensitive a body part is. The fingers and thumb, lips, nose, cheeks, and big toe are the most sensitive. © McGraw Hill LLC 49  The Skin Senses: Touch, Pressure, Temperature, and Pain 2 Gate-control theory of pain: particular nerve receptors in the spinal cord lead to specific areas of the brain related to pain. When receptors are activated, a “gate” to the brain is opened. Another set of receptors can, when stimulated, close the “gate,” thereby reducing the pain. Competing stimuli. Psychological factors. Cultural differences. Inflammatory pain vs. neuropathic pain © McGraw Hill LLC 50  Gate Control Theory of Pain © McGraw Hill LLC 51 51  The Gestalt Laws of Organization 1 Gestalt laws of organization: a series of classic principles in psychology that describe how we organize bits and pieces of information into meaningful wholes. 1) Closure: we usually group elements to form enclosed or complete figures rather than open ones. 2) Proximity: we perceive elements that are closer together as grouped together. © McGraw Hill LLC 52  The Gestalt Laws of Organization 2 3) Similarity: elements that are similar in appearance, we perceive as grouped together. 4) The overriding Gestalt principle is simplicity: when we observe a pattern, we perceive it in the most basic, straightforward manner that we can. © McGraw Hill LLC 53  MODULE 11 FIGURE 2 Organizing these various bits and pieces of information into meaningful wholes constitutes some of the most basic processes of perception, which are summed up in the gestalt laws of organization. © McGraw Hill LLC 54  Figure/Ground When the usual cues we use to distinguish figure from ground are absent, we may shift back and forth between different views of the same figure. In (a), you can see either a vase or the profiles of two people. In (b), the shaded portion of the figure, called a Necker cube, can appear to be either the front or the back of the cube. © McGraw Hill LLC 55