PSYC 1313_Chapter 3_ToPost.pptx

CHAPTER 3 Sensation and Perception  AGENDA Attendance This Week: Chapter 3 – Sensation & Perception Upcoming Next Week: Learning Chapter Friday, September 13 – Exam 1 at 1:00 PM O u r S e n s a t i o n a l S e n s e s v s. Pe r c e p t i o n s...

CHAPTER 3 Sensation and Perception  AGENDA Attendance This Week: Chapter 3 – Sensation & Perception Upcoming Next Week: Learning Chapter Friday, September 13 – Exam 1 at 1:00 PM O u r S e n s a t i o n a l S e n s e s v s. Pe r c e p t i o n s The Riddle of Separate Sensations Sensation –The detection of physical energy emitted by physical objects Perception –A set of mental operations that organizes sensory impulses into meaningful patterns  OUR SENSATIONAL SENSES The Riddle of Separate Sensations Sense receptors Specialized cells that convert physical energy into electrical energy that can be transmitted as nerve impulses to the brain 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 Synesthesia – A condition in which stimulation of one sense also evokes another Figure 3.1 The General Process of Sensation Although the individual senses respond to different kinds of energy in the world, the overall process of sensation is the same. Our Sensational Senses Measuring the Senses – Psychophysics ▪The study of how the physical properties of a stimulus are related to our psychological experience of that stimulus – Absolute threshold ▪The smallest quantity of physical energy that can be reliably detected by an observer Measuring the Senses Our absolute thresholds – Vision A single candle flame from 30 miles on a clear night – Smell One drop of perfume in a 3-room apartment – Touch The wing of a bee falling on the cheek from 1 cm – Taste One teaspoon of sugar in 2 gallons of water Figure 3.2 The Visible Spectrum of Electromagnetic Energy Our visual system detects only a small fraction of the electromagnetic energy around us.  OUR SENSATIONAL SENSES Measuring the Senses Difference Threshold – The smallest difference in stimulation that can be reliably detected by an observer when two stimuli are compared – Also called the Just Noticeable Difference (JND)  OUR SENSATIONAL SENSES Measuring the Senses Signal-Detection Theory A psychophysical theory that divides the detection of a sensory signal into a sensory process and a decision process Four possible outcomes: Detecting a present signal (“a hit”) Detecting a signal that is absent (“false alarm”) Fail to detect a present signal (“a miss”) Correctly say that an absent signal is not there (“a correct rejection”)  Our Sensational Senses Sensory Adaptation – The reduction or disappearance of sensory responsiveness when stimulation is unchanging or repetitious – Spares us from having to continuously respond to unimportant information Sensory Deprivation – The absence of normal levels of sensory stimulation Change and Contrast Sensation depends on change and contrast in the environment. Hold your hand over one eye and stare at the dot in the middle of the circle on the right. You should have no trouble maintaining an image of the circle. However, if you do the same with the circle on the left, the image will fade. The gradual change from light to dark does not provide enough contrast to keep your visual receptors firing at a steady rate. The circle reappears only if you close and reopen your eye or shift your gaze to the X.  Our Sensational Senses Sensing without Perceiving Selective attention – The focusing of attention on selected aspects of the environment and the blocking out of others Inattentional blindness – Failure to consciously perceive something you are looking at because you are not attending to it – One of the hazards of selective attention  WHICH IS CORRECT? Jane has prepared three cups of coffee, but can’t recall how much sugar is in each. The cup with the smallest amount of sugar is easy to identify, but Jane can’t taste any difference between the other two cups even though she knows one has more sugar. This describes which of the following concepts? A. Distribution of receptors B. Optimal levels of stimulation C. Sensory adaptation D. Difference threshold E. Signal detection theory  WHICH IS CORRECT? Jane has prepared three cups of coffee, but can’t recall how much sugar is in each. The cup with the smallest amount of sugar is easy to identify, but Jane can’t taste any difference between the other two cups even though she knows one has more sugar. This describes which of the following concepts? Correct answer: Difference threshold  WHICH IS CORRECT? John is looking all over for his glasses when his wife points them out at the top of his head. This describes which of the following concepts? A. Distribution of receptors B. Optimal levels of stimulation C. Sensory adaptation D. Difference threshold E. Signal detection theory  WHICH IS CORRECT? (4 OF 10) John is looking all over for his glasses when his wife points them out at the top of his head. This describes which of the following concepts? Correct answer: Sensory adaptation Vision What We See Hue – Visual experience specified by color names and related to the wavelength of light Brightness – Visual experience related to the amount of light emitted from or reflected by an object Saturation – Visual experience related to the complexity of light waves; vividness or purity of color Figure 3.3 What We See Variations in brightness, hue, and saturation represent psychological dimensions of vision that correspond to the intensity, wavelength, and complexity of wavelengths of light. Vision An Eye on the World Retina – Neural tissue lining the back of the eyeball’s interior containing visual receptors Rods – Visual receptors that respond to dim light Cones – Visual receptors involved in color vision Color Visio n Video  VISION An Eye on the World Dark adaptation – A process by which visual receptors become maximally sensitive to dim light Ganglion cells – Neurons in the retina of the eye, which gather information from receptor cells – Their axons make up the optic nerve Figure 3.5 The Retinal Image  YOUR TURN You have a hard time locating your red car at night, in the poorly lit mall parking lot. Why? A. Your rods are less sensitive to color in dim light. B. Your cones, which detect color, do not function well in dim light. C. Your ganglion cells receive insufficient overall stimulation to function. D. Your rods, which detect color, do not function well in dim light.  YOUR TURN (2 OF 4) You have a hard time locating your red car at night, in the poorly lit mall parking lot. Why? Correct answer: Your cones, which detect color, do not function well in dim light. Vision Why the Visual System is Not a Camera Feature-detector cells – Cells in the visual cortex that are sensitive to specific features of the environment Much visual processing is done in the brain. Some cortical cells respond to lines in specific orientations (e.g., horizontal) Other cortical cells respond to other shapes (e.g., bulls-eyes, spirals, faces) Vision How We See Colors The trichromatic theory –Also called the Young-Helmholtz theory –Proposed that the eye has 3 different cones that detect 3 different colors –Red, blue, and green –All other colors are derived by combination. –Malfunctioning of different cones explains different forms of color-blindness  VISION How We See Colors The opponent-process theory – A competing theory of color vision, which assumes that the visual system treats pairs of colors as opposing or antagonistic – Red-green pair – Blue-yellow pair – Black-white pair – Opponent-process cells are inhibited by a color, and have a burst of activity when it is removed – This explains negative afterimages  Figure 3.8 A Change of Heart Opponent-process cells that switch on or off in response to green send an opposite message—“red”—when the green is removed, producing a negative afterimage. Stare at the black dot in the middle of this heart for at least 20 seconds. Then shift your gaze to a white piece of paper or a white wall. Do you get a “change of heart”? You should see an image of a red or pinkish heart with a blue border. Vision Constructing the Visual World Form perception –Gestalt principles describe the brain’s organization of sensory building blocks into meaningful units and patterns  VISION Constructing the Visual World – Proximity Things that are near each other are grouped together  VISION Constructing the Visual World – Closure The brain tends to fill in gaps to perceive complete forms  VISION Constructing the Visual World Similarity Things that are alike are perceived as belonging together  VISION Constructing the Visual World – Continuity Seeing continuity in lines that could be interpreted as either continuous or abruptly shifting in direction  YOUR TURN (3 OF 4) Which Gestalt principle is illustrated by the fact that we see columns rather than rows of dots in this diagram? 1. Similarity 2. Proximity 3. Closure 4. Continuity  YOUR TURN (4 OF 4) Which Gestalt principle is illustrated by the fact that we see columns rather than rows of dots in this diagram? Correct answer: Proximity  VISION Constructing the Visual World Depth and distance perception – Binocular cues – Visual cues to depth or distance requiring two eyes – Convergence – Turning inward of the eyes, which occurs when they focus on a nearby object  VISION Constructing the Visual World Depth and distance perception – Retinal disparity – The slight difference in lateral separation between two objects as seen by the right and left eyes – Monocular cues – Visual cues to depth or distance which can be used by one eye alone  VISION Constructing the Visual World Visual constancies: when seeing is believing – Perceptual constancy The accurate perception of objects as stable or unchanged despite changes in the sensory patterns they produce – Size constancy – Shape constancy – Location constancy – Brightness constancy – Color constancy  WHICH IS CORRECT? A friend is walking toward you, but does not seem to be growing in size. This is called __________. A. shape constancy B. location constancy C. size constancy D. brightness constancy E. color constancy  WHICH IS CORRECT? A friend is walking toward you, but does not seem to be growing in size. This is called __________. Correct answer: size constancy  WHICH IS CORRECT? Snow remains white even on a cloudy day, and a black car remains black even on a sunny day. This is called ________. A. shape constancy B. location constancy C. size constancy D. brightness constancy E. color constancy  WHICH IS CORRECT? (10 OF 10) Snow remains white even on a cloudy day, and a black car remains black even on a sunny day. This is called ________. Correct answer: color constancy  VISION Constructing the Visual World Visual illusions: When seeing is misleading – Perceptual illusion – Systematic errors that provide us with hints about the perceptual strategies of the mind Figure 3.10 The Müller-Lyer Illusion The two lines in (a) are exactly the same length. We are usually fooled into perceiving them as different because the brain interprets the one with the outward-facing branches as farther away, as if it were the far corner of a room, and the one with the inward-facing branches as closer, as if it were the near edge of a building (b). Figure 3.11 Color in Context The way you perceive a color depends on the color surrounding it. In this example, the small squares are exactly the same color and brightness. Figure 3.12 Fooling the Eye Although perception is usually accurate, we can be fooled. In (a), the cats as drawn are exactly the same size; in (b), the diagonal lines are all parallel. To see the illusion depicted in (c), hold your index fingers 5 to 10 inches in front of your eyes as shown and then focus straight ahead. Do you see a floating “fingertip frankfurter”? Can you make it shrink or expand?  WHAT DO YOU THINK? Illusions are valuable because they are systematic errors that provide us with hints about the perceptual strategies of the mind. A. True B. False  WHAT DO YOU THINK? Illusions are valuable because they are systematic errors that provide us with hints about the perceptual strategies of the mind. Correct answer: True Hearing What We Hear Loudness – The dimension of auditory experience related to the intensity of a pressure wave – Measured in decibels (dB) Pitch – The dimension of auditory experience related to the frequency of a pressure wave; – Measured in hertz (Hz) Hearing What We Hear Timbre – The dimension of auditory experience related to the complexity of a pressure wave – Indicates the purity of a tone Hearing An Ear on the World Organ of Corti –A structure in the cochlea containing hair cells that serve as the receptors for hearing Cochlea –A snail-shaped, fluid-filled organ in the inner ear, containing the organ of Corti –The receptors for hearing are located here Hearing Constructing the Auditory World Gestalt principles in the auditory world –Figure –Ground –Proximity –Continuity –Similarity –Closure –Distance –Direction  WHAT DO YOU THINK? A sound arriving from the right reaches the right ear at the same time it reaches the left ear. A. True B. False  WHAT DO YOU THINK? A sound arriving from the right reaches the right ear at the same time it reaches the left ear. Correct answer: True Other Senses Taste: Savory Sensations Papillae –Knoblike elevations on the tongue, containing the taste buds Taste buds –Nests of taste-receptor cells  OTHER SENSES Taste: Savory Sensations Four basic tastes – Salty, sour, bitter, sweet – Umami (taste of MSG) disputed Different people have different tastes based on – Genetics – Culture – Learning Figure 3.15 Taste Test The green bars show the percentages of people who could identify a substance dropped on the tongue when they were able to smell it. The purple bars show the percentage that could identify the substance when they were prevented from smelling it (Mozell et al., 1969).  WHAT DO YOU THINK? The basic tastes (e.g., salty, sweet, etc.) are part of our evolutionary heritage. A. True B. False  WHAT DO YOU THINK? The basic tastes (e.g., salty, sweet, etc.) are part of our evolutionary heritage. Correct answer: True  Other Senses 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  WHAT DO YOU KNOW? Odors can have a psychological effect on you. A. True B. False  WHAT DO YOU KNOW? Odors can have a psychological effect on you. Correct answer: True Other Senses Senses of the Skin Basic skin senses –touch (or pressure) –warmth –cold –pain Variations within these four include –Itch, tickle, painful burning Other Senses The Mystery of Pain Gate-control theory –The experience of pain depends in part on whether pain impulses get past a neurological “gate” in the spinal cord and thus reach the brain –This may be why rubbing an arm or leg after painfully bumping it may create a reduction in the pain of the injury  OTHER SENSES The Mystery of Pain Phantom pain – The experience of pain in a missing limb or other body part – “Mirror therapy” fools the brain into thinking its owner has two healthy limbs – In most cases, phantom pain disappears  WHAT DO YOU THINK? Sometimes the sensation of pain can linger a long time after the pain inducing stimulus is removed. A. True B. False  WHAT DO YOU THINK? Sometimes the sensation of pain can linger a long time after the pain inducing stimulus is removed. Correct answer: True