Sarah Grison Todd Heatherton Michael Gazzaniga Psychology in Your Life FIRST EDITION Chapter 5 Sensation and Perception 2014 W. W. Norton & Company, Inc.
Section 5.1 How Do Sensation and Perception Affect Us?
Sensation 5.1 How Do Sensation and Perception Affect Us? The sense organs detection of external physical stimulus and the transmission of information about this stimulus to the brain Perception The processing, organization, and interpretation of sensory signals in the brain; these processes result in an internal neural representation of the physical stimulus
Our Senses Detect Physical Stimuli, and Our Brains Process Perception From sensation to perception Sensory receptors: Sensory organs that detect physical stimulation from the external world and change that stimulation into information that can be processed by the brain Transduction: A process by which sensory receptors change physical stimuli into signals that are eventually sent to the brain See figures 5.2, 5.3 next slide
There Must Be a Certain Amount of a Stimulus for Us to Detect It Threshold to detect sensory information Absolute threshold: The smallest amount of physical stimulation required to detect a sensory input half of the time it is present Difference threshold: The minimum difference in physical stimulation required to detect a difference between sensory inputs Weber s law Just noticeable difference See figure 5.4 and table 5.1 next slide
There Must Be a Certain Amount of a Stimulus for Us to Detect It Signal detection theory Signal detection theory: Detection of a faint stimulus requires a judgment it is not an allor-none process See figures 5.5a, 5.5b next slide
There Must Be a Certain Amount of a Stimulus for Us to Detect It Sensory adaptation Sensory adaptation: A decrease in sensitivity to a constant level of stimulation
Section 5.2 How Do We See?
5.2 How Do We See? Every time you open your eyes, nearly half your brain springs into action
Sensory Receptors in Our Eyes Detect Light Focusing light in the eye The waves pass through the cornea of your eye The light then passes through the pupil The iris, a circular muscle, gives eyes their color and controls the pupil s size to determine how much light enters the eye
Sensory Receptors in Our Eyes Detect Light Focusing light in the eye Lens: The adjustable, transparent structure behind the pupil; this structure focuses light on the retina, resulting in a crisp visual image See figure 5.6 step 1 & 2 next slide
Sensory Receptors in Our Eyes Rods and cones Detect Light Retina: The thin inner surface of the back of the eyeball; this surface contains the sensory receptors Rods: Sensory receptors in the retina that detect light waves and transduce them into signals that are processed in the brain as vision. Rods respond best to low levels of illumination, and therefore do not support color vision or detection of fine detail
Sensory Receptors in Our Eyes Rods and cones Detect Light Cones: Sensory receptors in the retina that detect light waves and transduce them into signals that are processed in the brain as vision. Cones respond best to higher levels of illumination, and therefore they are responsible for seeing color and fine detail Each retina holds approximately 120 million rods and 6 million cones. Near the center of the retina is a small region called the fovea where cones are densely packed
Sensory Receptors in Our Eyes Detect Light From the eye to the brain Information about what the eye has sensed is delivered to the ganglion cells The axons of each ganglion cell are gathered into a bundle. This bundle is called the optic nerve Blind spots in your left and right visual fields, where the optic nerve exits the retina
Sensory Receptors in Our Eyes Detect Light From the eye to the brain Half of the axons in the optic nerves cross to the other side of the brain. The rest of the axons stay on the same side of the brain. The point where the axons cross is known as the optic chiasm The information passes through the thalamus and travels to the primary visual cortex in the occipital lobes See figure 5.6 step 3 & 4 next slide
We Perceive Color Based on Physical Aspects of Light Physical experience of color The amplitude is the height of the light wave from base to peak; people experience this quality as brightness The wavelength of the light wave is the distance from peak to peak. This distance determines your perception of both hue and saturation
We Perceive Color Based on Physical Aspects of Light Physical experience of color Hue refers to the distinctive characteristics that place a particular color in the spectrum Saturation is the intensity of the color See figures 5.7, 5.8 next slide
We Perceive Color Based on Physical Aspects of Light Trichromatic theory Trichromatic theory: There are three types of cone receptor cells in the retina that are responsible for color perception. Each type responds optimally to different but overlapping ranges of wavelengths See figure 5.9 next slide
We Perceive Color Based on Physical Aspects of Light Trichromatic theory The combining of wavelengths is called additive color mixing The combining of pigments is called subtractive color mixing See figures 5.10a, 5.10b next slide
We Perceive Color Based on Physical Aspects of Light Opponent-process theory Opponent-process theory: The proposal that ganglion cells in the retina receive excitatory input from one type of cone and inhibitory input from another type of cone, creating the perception that some colors are opposites See figure 5.11 next slide
We Perceive Objects by Organizing Visual Information The founders of Gestalt psychology postulated a series of laws to explain how our brains group the perceived features of a visual scene into organized wholes Figure and ground Figure ground: An object is a figure that is distinct from the background. The background is referred to as the ground See figure 5.12 next slide
We Perceive Objects by Organizing Grouping Visual Information Grouping: The visual system s organization of features and regions to create the perception of a whole, unified object Group visual information based on the proximity of parts and by the similarity of parts See figure 5.13 next slide
We Perceive Objects by Organizing Visual Information Bottom-up and top-down processing Bottom-up processing: The perception of objects is due to analysis of environmental stimulus input by sensory receptors; this analysis then influences the more complex, conceptual processing of that information in the brain
We Perceive Objects by Organizing Visual Information Bottom-up and top-down processing Top-down processing: The perception of objects is due to the complex analysis of prior experiences and expectations within the brain; this analysis influences how sensory receptors process stimulus input from the environment
When We Perceive Depth, We Can Locate Objects in Space Binocular depth cues Cues of depth perception that arise because people have two eyes Monocular depth cues Cues of depth perception that are available to each eye alone
When We Perceive Depth, We Can Locate Objects in Space Binocular depth perception Binocular Disparity: We use both eyes to perceive depth through binocular disparity, where each retina has a slightly different view of the world See figure 5.15 next slide
When We Perceive Depth, We Can Locate Objects in Space Monocular depth perception Pictorial depth cues; occlusion, height in field, relative size, familiar size, linear perspective, and texture gradient See figure 5.16 next slide
Cues in Our Brains and in the World Allow Us to Perceive Motion Motion aftereffects Motion aftereffects may occur when you gaze at a moving image for a long time and then look at a stationary scene Stroboscopic motion Movies are made up of still images. Each image is slightly different from the one before it. When the series is presented fast enough, we perceive the illusion of motion pictures. This perceptual illusion is called stroboscopic motion
Section 5.3 How Do We Hear?
5.3 How Do We Hear? Hearing is also called audition. This sensory mechanism enables us to determine what is happening in our environments. It provides a medium for spoken language. It brings pleasure to our lives (through music, for example)
Auditory Receptors in Our Ears Detect Sound Waves From the ear to the brain The process of hearing begins when sound waves arrive at the shell-shaped structure of your outer ear Eardrum: A thin membrane that marks the beginning of the middle ear; sound waves cause the eardrum to vibrate See figure 5.18a next slide
Auditory Receptors in Our Ears Detect Sound Waves From the ear to the brain Cochlea: A coiled, bony, fluid-filled tube in the inner ear that houses the sensory receptors Hair cells: Sensory receptors located in the cochlea that detect sound waves and transduce them into signals that ultimately are processed in the brain as sound See figure 5.18b next slide
Auditory Receptors in Our Ears Detect Sound Waves From the ear to the brain Transduction initiates the creation of action potentials in the auditory nerve. The auditory nerve sends the information to the sensory processing center of the thalamus and finally to the primary auditory cortex in the brain See figure 5.18c next slide
We Perceive Sound Based on Physical Aspects of Sound Waves Loudness and pitch of sounds The height of the sound waves is called the amplitude. Amplitude determines our perception of loudness The distance between peaks of sound waves is the wavelength. The time between the peaks in wavelength is called the frequency. The frequency of the waves determines the pitch of the sound, from high to low See figure 5.19 next slide
We Perceive Sound Based on Physical Aspects of Sound Waves Temporal and place coding Temporal coding: The perception of lowerpitched sounds is a result of the rate at which hair cells are stimulated by sound waves of lower frequencies Place coding: The perception of higherpitched sounds depends on the point on the basilar membrane where hair cells are stimulated by sound waves of varying higher frequencies
We Perceive Sound Based on Physical Aspects of Sound Waves Localization The ear estimates the location of a sound based first on when the sound arrives and second on the amplitude, or intensity, of the sound wave See figure 5.20 next slide
Section 5.4 How Can We Taste and Smell?
5.4 How Can We Taste and Smell? Together, taste and smell produce the experience of flavor. In fact, flavor is based more on smell than on taste The sense of taste is also called gustation The sense of smell is also called olfaction
Receptors in Our Taste Buds Detect Chemical Molecules From mouth to brain Taste buds: Structures, located in papillae on the tongue, that contain the sensory receptors Called taste receptors Papillae: Structures on the tongue that contain groupings of taste buds See figure 5.21 next slide
Receptors in Our Taste Buds Detect Chemical Molecules Five main tastes Sweet, sour, salty, bitter, and umami (Japanese for savory or yummy ). Umami was discovered in 2007 and is the most recently recognized taste sensation Supertasters are highly aware of flavors and textures and are more likely than others to feel pain when eating very spicy foods. Supertasters have nearly six times as many taste buds as normal tasters
Receptors in Our Taste Buds Detect Chemical Molecules Taste preference Texture of food also affects taste preferences Whether the food causes discomfort Cultural influences on food preferences begin in the womb
Our Olfactory Receptors Detect Odorants When a dog is out for a walk, why does it sniff virtually every object and creature it encounters? The sense of smell, which is also called olfaction, is the dog s main way of perceiving the world
Our Olfactory Receptors Detect Odorants From the nose to the brain Olfactory epithelium: A thin layer of tissue, deep within the nasal cavity, that contains the olfactory receptors; these sensory receptors produce information that is processed in the brain as smell Chemical molecules are called odorants
Our Olfactory Receptors Detect Odorants From the nose to the brain Olfactory bulb: A brain structure above the olfactory epithelium in the nasal cavity; from this structure, the olfactory nerve carries information about smell to the brain See figure 5.22 next slide
Our Olfactory Receptors Detect Odorants Ten thousand smells Humans can detect about 10,000 smells, but researchers are still exploring how the receptors transduce odorants into the perception of these distinct smells
Our Olfactory Receptors Smell perception Detect Odorants Information about whether a smell is pleasant or unpleasant is processed in the brain s prefrontal cortex
Section 5.5 How Do We Feel Touch and Pain?
5.5 How Do We Feel Touch and Pain? When you see, hear, taste, or smell something, receptors in just one small part of your body have been stimulated. But touch receptors exist all over your body. In fact, the skin is the largest organ for sensory reception
Receptors in Our Skin Detect Temperature and Pressure From skin to the brain Warm receptors: Sensory receptors in the skin that detect the temperature of stimuli and transduce it into information processed in the brain as warmth Cold receptors: Sensory receptors in the skin that detect the temperature of stimuli and transduce it into information processed in the brain as cold
Receptors in Our Skin Detect Temperature and Pressure From skin to the brain Pressure receptors: Sensory receptors in the skin that detect tactile stimulation and transduce it into information processed in the brain as different types of pressure on the skin Touch information travels first through the thalamus and then to the somatosensory cortex, which processes the information See figure 5.23 next slide
Receptors in Our Skin Detect Temperature and Pressure Perception of touch Penfield discovered that electrical stimulation of the primary somatosensory cortex could evoke the perception of touch in different regions of the body For the most sensitive regions of the body, such as lips and fingers, a great deal of the cortex is dedicated to processing touch
We Detect Pain in Our Skin and Throughout the Body Two types of pain receptors Fast fibers: Sensory receptors in the skin, muscles, organs, and membranes around both bones and joints; these myelinated fibers quickly convey intense sensory input to the brain, where it is perceived as sharp, immediate pain
We Detect Pain in Our Skin and Throughout the Body Two types of pain receptors Slow fibers: Sensory receptors in the skin, muscles, organs, and membranes around both bones and joints; these unmyelinated fibers slowly convey intense sensory input to the brain, where it is perceived as chronic, dull, steady pain
We Detect Pain in Our Skin and Throughout the Body Controlling pain Distraction can reduce your perception of pain Listening to music is an extremely effective way to reduce postoperative pain, perhaps because it helps patients relax
Internal Sensory Systems Help Us Function in Space Our kinesthetic sense tells us how our body and limbs are positioned in space Kinesthetic sensations come from receptors in muscles, tendons, and joints Our vestibular sense allows us to maintain balance The vestibular sense uses information from receptors in structures of the inner ear called the semicircular canals