Chapter 6

7. Nociceptors initiate the sensation of

pain

feature detectors

: nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement. (p. 241)

How does the eye transform light energy into neural messages?

After entering the eye and being focused by a lens, light-energy particles strike the eye's inner surface, the retina. The retina's light-sensitive rods and color-sensitive cones convert the light energy into neural impulses which, after processing by bipolar and ganglion cells, travel through the optic nerve to the brain.

How do we perceive motion?

As objects move, we assume that shrinking objects are retreating and enlarging objects are approaching. But sometimes we miscalculate. A quick succession of images on the retina can create an illusion of movement, as in stroboscopic movement or the phi phenomenon

What are the common causes of hearing loss, and why does controversy surround cochlear implants?

Conduction hearing loss results from damage to the mechanical system that transmits sound waves to the cochlea. Sensorineural hearing loss (or nerve deafness) results from damage to the cochlea's hair cells or their associated nerves. Diseases and accidents can cause hearing loss, but age-related disorders and prolonged exposure to loud noises are more common causes. Artificial cochlear implants can restore hearing for some people, but members of the Deaf culture movement believe cochlear implants are unnecessary for people who have been Deaf from birth and who can speak their own language, sign.

How do we see the world in three dimensions?

Depth perception is our ability to see objects in three dimensions and judge distance. The visual cliff and other research demonstrates that many species perceive the world in three dimensions at, or very soon after, birth. Binocular cues, such as retinal disparity, are depth cues that rely on information from both eyes. Monocular cues (such as relative size, interposition, relative height, relative motion, linear perspective, and light and shadow) let us judge depth using information transmitted by only one eye.

4: What is the energy that we see as visible light?

Each sense receives stimulation, transforms (transduces) it into neural signals, and sends these neural messages to the brain. In vision, the signals consist of light-energy particles from a thin slice of the broad spectrum of electromagnetic radiation. The hue we perceive in a light depends on its wavelength, and its brightness depends on its intensity.

How did the Gestalt psychologists understand perceptual organization?

Gestalt psychologists searched for rules by which the brain organizes fragments of sensory data into gestalts (from the German word for "whole"), or meaningful forms. In pointing out that the whole is more than the sum of its parts, they noted that we filter sensory information and infer perceptions in ways that make sense to us.

4. The frequency of a sound wave is measured in:

Hertz

How do human factors psychologists work to create user-friendly machines and work settings?

Human factors psychologists contribute to human safety and improved design by encouraging developers and designers to consider human perceptual abilities, to avoid the curse of knowledge, and to test users to reveal perception-based problems.

How does the brain process visual information?

Impulses travel along the optic nerve, to the thalamus, and on to the visual cortex. In the visual cortex, feature detectors respond to specific features of the visual stimulus. Higher-level supercells integrate this pool of data for processing in other cortical areas. Parallel processing in the brain handles many aspects of a problem simultaneously, and separate neural teams work on visual subtasks (color, movement, depth, and form). Other neural teams integrate the results, comparing them with stored information, and enabling perceptions.

2: What are the absolute and difference thresholds, and do stimuli below the absolute threshold have any influence?

Our absolute threshold for any stimulus is the minimum stimulation necessary for us to be consciously aware of it 50 percent of the time. Signal detection theory demonstrates that individual absolute thresholds vary, depending on the strength of the signal and also on our experience, expectations, motivation, and alertness. Our difference threshold (also called just noticeable difference, or jnd) is the barely noticeable difference we discern between two stimuli 50 percent of the time. Priming shows that we can process some information from stimuli below our absolute threshold for conscious awareness. But the effect is too fleeting to enable people to exploit us with subliminal messages. Weber's law states that two stimuli must differ by a constant proportion to be perceived as different.

How do we sense touch and sense our body's position and movement? How do we experience pain?

Our sense of touch is actually several senses—pressure, warmth, cold, and pain—that combine to produce other sensations, such as "hot." Through kinesthesis, we sense the position and movement of body parts. We monitor the body's position and maintain our balance with our vestibular sense. Pain is an alarm system that draws our attention to some physical problem. One theory of pain is that a "gate" in the spinal cord either opens to permit pain signals traveling up small nerve fibers to reach the brain, or closes to prevent their passage. The biopsychosocial approach views pain as the sum of three sets of forces: biological influences, such as nerve fibers sending messages to the brain; psychological influences, such as our expectations; and social-cultural influences, such as the presence of others. Treatments to control pain often combine physiological and psychological elements.

How adaptable is our ability to perceive?

Perceptual adaptation is evident when people are given glasses that shift the world slightly to the left or right, or even upsidedown. People are initially disoriented, but they manage to adapt to their new context.

How do perceptual constancies help us organize our sensations into meaningful perceptions?

Perceptual constancy enables us to perceive objects as stable despite the changing image they cast on our retinas. Shape constancy is our ability to perceive familiar objects (such as an opening door) as unchanging in shape. Size constancy is perceiving objects as unchanging in size despite their changing retinal images. Knowing an object's size gives us clues to its distance; knowing its distance gives clues about its size, but we sometimes misread monocular distance cues and reach the wrong conclusions, as in the Moon illusion. Lightness (or brightness) constancy is our ability to perceive an object as having a constant lightness even when its illumination—the light cast upon it—changes. The brain perceives lightness relative to surrounding objects. Color constancy is our ability to perceive consistent color in objects, even though the lighting and wavelengths shift. Our brain constructs our experience of the color of an object through comparisons with other surrounding objects.

How do our expectations, contexts, and emotions influence our perceptions?

Perceptual set is a mental predisposition that functions as a lens through which we perceive the world. Our learned concepts (schemas) prime us to organize and interpret ambiguous stimuli in certain ways. The surrounding context helps create expectations that guide our perceptions. Emotional context can color our interpretation of other people's behaviors, as well as our own.

What theories help us understand pitch perception?

Place theory proposes that our brain interprets a particular pitch by decoding the place where a sound wave stimulates the cochlea's basilar membrane. Frequency theory proposes that the brain deciphers the frequency of the pulses traveling to the brain. Place theory explains how we hear high-pitched sounds, but it cannot explain how we hear low-pitched sounds. Frequency theory explains how we hear low-pitched sounds, but it cannot explain how we hear high-pitched sounds. Some combination of the two helps explain how we hear sounds in the middle range.

1: What are sensation and perception? What do we mean by bottom-up processing and top-down processing?

Sensation is the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment. Perception is the process of organizing and interpreting this information. Although we view sensation and perception separately to analyze and discuss them, they are actually parts of one continuous process. Bottom-up processing is sensory analysis that begins at the entry level, with information flowing from the sensory receptors to the brain. Top-down processing is analysis that begins with the brain and flows down, filtering information through our experience and expectations to produce perceptions.

3: What is the function of sensory adaptation?

Sensory adaptation (our diminished sensitivity to constant or routine odors, sounds, and touches) focuses our attention on informative changes in our environment.

What are the characteristics of air pressure waves that we hear as sound?

Sound waves are bands of compressed and expanded air. Our ears detect these changes in air pressure and transform them into neural impulses, which the brain decodes as sound. Sound waves vary in frequency, which we experience as differing pitch, and amplitude, which we perceive as differing loudness.

How do we locate sounds?

Sound waves strike one ear sooner and more intensely than the other. The brain analyzes the minute differences in the sounds received by the two ears and computes the sound's source.

How do we experience taste?

Taste, a chemical sense, is a composite of five basic sensations—sweet, sour, salty, bitter, and umami—and of the aromas that interact with information from the taste receptor cells of the taste buds. The influence of smell on our sense of taste is an example of sensory interaction, the ability of one sense to influence another.

What theories help us understand colorvision?

The Young-Helmholtz trichromatic (three-color) theory proposed that the retina contains three types of color receptors. Contemporary research has found three types of cones, each most sensitive to the wavelengths of one of the three primary colors of light (red, green, or blue). Hering's opponent-process theory proposed three additional color processes (red-versus-green, blue-versus-yellow, black-versus-white). Contemporary research has confirmed that, en route to the brain, neurons in the retina and the thalamus code the color-related information from the cones into pairs of opponent colors. These two theories, and the research supporting them, show that color processing occurs in two stages.

How does the ear transform sound energy into neural messages?

The outer ear is the visible portion of the ear. The middle ear is the chamber between the eardrum and cochlea. The inner ear consists of the cochlea, semicircular canals, and vestibular sacs. Through a mechanical chain of events, sound waves traveling through the auditory canal cause tiny vibrations in the eardrum. The bones of the middle ear amplify the vibrations and relay them to the fluid-filled cochlea. Rippling of the basilar membrane, caused by pressure changes in the cochlear fluid, causes movement of the tiny hair cells, triggering neural messages to be sent (via the thalamus) to the auditory cortex in the brain.

What are the claims of ESP, and what have most research psychologists concluded after putting these claims to the test?

The three most testable forms of extrasensory perception (ESP) are telepathy (mind-to-mind communication), clairvoyance (perceiving remote events), and precognition (perceiving future events). Most research psychologists' skepticism focuses on two points. First, to believe in ESP, you must believe the brain is capable of perceiving without sensory input. Second, psychologists and parapsychologists have been unable to replicate (reproduce) ESP phenomena under controlled conditions.

How do we experience smell?

There are no basic sensations for smell. Smell is a chemical sense. Some 5 million olfactory receptor cells, with their approximately 350 different receptor proteins, recognize individual odor molecules. The receptor cells send messages to the brain's olfactory bulb, then to the temporal lobe and to parts of the limbic system. Odors can spontaneously evoke memories and feelings, due in part to the close connections between brain areas that process smell and memory.

How do figure-ground and grouping principles contribute to our perceptions?

To recognize an object, we must first perceive it (see it as a figure) as distinct from its surroundings (the ground). We bring order and form to stimuli by organizing them into meaningful groups, following the rules of proximity, similarity, continuity, connectedness, and closure.

retinal disparity:

a binocular cue for perceiving depth: By comparing images from the retinas in the two eyes, the brain computes distance—the greater the disparity (difference) between the two images, the closer the object. (p. 267)

cochlea: [KOHK-lee-uh]

a coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses. (p. 246)

cochlear implant:

a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea. (p. 250)

visual cliff:

a laboratory device for testing depth perception in infants and young animals. (p. 266)

perceptual set:

a mental predisposition to perceive one thing and not another. (p. 275)

iris:

a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening. (p. 237)

signal detection theory:

a theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes there is no single absolute threshold and that detection depends partly on a person's experience, expectations, motivation, and level of fatigue. (p. 231)

pitch:

a tone's experienced highness or lowness; depends on frequency. (p. 246)

12. Immanuel Kant and John Locke would have been most likely to disagree about the extent to which perception is influenced by

a. cultural experience.

11. The Moon illusion refers to our tendency to perceive the Moon as unusually

a. large when it is near the horizon.

10. Railroad tracks appear to converge in the distance. This provides a cue for depth perception known as

a. linear perspective.

13. After some practice, Carol was able to read books while holding them upside down. This best illustrates

a. perceptual adaptation.

3. Multiple ________ send combined messages to a bipolar cell, whereas a single ________ may link directly to a single bipolar cell.

a. rods; cone

5. In the Poggendorf illusion involving a rectangular post with a line segment protruding from each side, most people fail to correctly align the two line segments because they:

a. underestimate the width of the rectangular post.

5. The opponent-process theory explains why we would see a ________ afterimage after staring at a blue object.

a. yellow

5. The opponent-process theory is most useful for explaining a characteristic of

afterimages.

phi phenomenon:

an illusion of movement created when two or more adjacent lights blink on and off in quick succession. (p. 269)

gestalt:

an organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes. (p. 263)

bottom-up processing:

analysis that begins with the sensory receptors and works up to the brain's integration of sensory information. (p. 230)

6. Damage to the basilar membrane is most likely to affect one's

b. audition.

3. In the Ponzo Illusion, most people ________ the length of the bar that appears to be more ________.

b. overestimate; distant

4. Some stroke victims lose the capacity to perceive motion but retain the capacity to perceive shapes and colors. Others lose the capacity to perceive colors but retain the capacity to perceive movement and form. These peculiar visual disabilities best illustrate our normal capacity for

b. parallel processing.

13. People perceive an adult-child pair as looking more alike when told they are parent and child. This best illustrates the impact of

b. perceptual set.

9. The way in which you quickly group the individual letters in this test item into separate words best illustrates the principle of

b. proximity.

7. The rubber-hand illusion best illustrates

b. sensory interaction.

5. Current understanding of pitch perception indicates that

b. some combination of place and frequency theories seems to handle the pitches in the intermediate range.

1. Interpreting new sensory information within the framework of a past memory illustrates

b. top-down processing.

subliminal:

below one's absolute threshold for conscious awareness. (p. 232)

8. Rules for organizing stimuli into coherent groups were first identified by

c. Gestalt psychologists.

2. The size of the difference threshold is greater for heavier objects than for lighter ones. This best illustrates

c. Weber's law.

2. The conversion of the mechanical energy produced by sound waves into neural impulses occurs in the:

c. cochlea.

4. The phenomenon of blindsight best illustrates that visual information can be processed without

c. conscious awareness.

2. The Ponzo Illusion illustrates that people judge the size of an object in terms of its perceived:

c. distance.

10. The fact that we recognize objects as having a consistent form regardless of changing viewing angles illustrates

c. perceptual constancy.

15. Psychics are unable to make millions of dollars betting on horse races. This undermines their claims to possess the power of

c. precognition.

3. The most common form of colorblindness is a(n) _______ color deficiency.

c. red-green

9. The distance between our right and left eyes functions to provide us with a cue for depth perception known as

c. retinal disparity.

2. If you move your watchband up your wrist an inch or so, you will feel it for only a few moments. This best illustrates

c. sensory adaptation.

11. A door casts an increasingly trapezoidal image on our retinas as it opens, yet we still perceive it as rectangular. This illustrates

c. shape constancy.

1. If a visual image is first presented subliminally, the chance of a person later recognizing the same briefly presented image is improved. This best illustrates

c. that information can be processed outside of conscious awareness.

8. Receptor cells for the vestibular sense send messages to the

cerebellum

transduction:

conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brains can interpret. (p. 236)

1. The stimulus energy underlying your experience of sound involves continuous changes in:

d. air pressure.

12. Grass seen through sunglasses appears equally as green as it does without glasses. This best illustrates

d. color constancy.

3. As compared to long objects, short objects vibrate ________ and produce sound waves of ________ frequency.

d. faster; higher

14. ATM machines are more complex than VCRs ever were but are easier to operate thanks to the efforts of

d. human factors psychologists.

6. The sensory experience of bending one's knees or raising one's arms exemplifies

d. kinesthesis.

14. After hearing that Bryce had served a prison sentence, Janet began to perceive his friendly behavior as insincere and manipulative. This best illustrates the impact of

d. perceptual set.

15. Racial and ethnic stereotypes can sometimes bias our perceptions of others' behaviors. This best illustrates the impact of

d. top-down processing.

4. In the horizontal/vertical illusion, most people perceive a ________ line as ________.

d. vertical; longer than an equally long horizontal line

4. When all three types of cones are stimulated at once, a person will see:

d. white.

monocular cues:

depth cues, such as interposition and linear perspective, available to either eye alone. (p. 267)

binocular cues:

depth cues, such as retinal disparity, that depend on the use of two eyes. (p. 266)

sensory adaptation:

diminished sensitivity as a consequence of constant stimulation. (p. 234)

place theory:

in hearing, the theory that links the pitch we hear with the place where the cochlea's membrane is stimulated. (p. 249)

frequency theory:

in hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch. (p. 249)

top-down processing:

information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations. (p. 230)

1. In the Müller-Lyer illusion, the arrowheads at the ends of the lines lead people to misjudge the ________ of the two horizontal lines.

length

color constancy:

perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object. (p. 271)

perceptual constancy:

perceiving objects as unchanging (having consistent shapes, size, lightness, and color) even as illumination and retinal images change. (p. 269)

cones:

retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine detail and give rise to color sensations. (p. 238)

rods:

retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond. (p. 238)

depth perception:

the ability to see objects in three dimensions although the images that strike the retina are two-dimensional; allows us to judge distance. (p. 266)

priming:

the activation, often unconsciously, of particular associations in memory. (p. 347)

pupil:

the adjustable opening in the center of the eye through which light enters. (p. 237)

intensity:

the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave's amplitude. (p. 237)

fovea:

the central focal point in the retina, around which the eye's cones cluster. (p. 239)

middle ear:

the chamber between the eardrum and cochlea containing three tiny bones (hammer, anvil, and stirrup) that concentrate the vibrations of the eardrum on the cochlea's oval window. (p. 246)

extrasensory perception (ESP):

the controversial claim that perception can occur apart from sensory input; includes telepathy, clairvoyance, and precognition. (p. 282)

hue:

the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth. (p. 237)

wavelength:

the distance from the peak of one light or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses of radio transmission. (p. 237)

inner ear:

the innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs. (p. 246)

retina:

the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information. (p. 237)

difference threshold:

the minimum difference between two stimuli required for detection 50 percent of the time. We experience the difference threshold as a just noticeable difference (or jnd). (p. 234)

absolute threshold:

the minimum stimulation needed to detect a particular stimulus 50 percent of the time. (p. 231)

optic nerve:

the nerve that carries neural impulses from the eye to the brain. (p. 238)

frequency

the number of complete wavelengths that pass a point in a given time (for example, per second). (p. 246)

figure-ground:

the organization of the visual field into objects (the figures) that stand out from their surroundings (the ground). (p. 264)

grouping:

the perceptual tendency to organize stimuli into coherent groups. (p. 265)

blind spot:

the point at which the optic nerve leaves the eye, creating a "blind" spot because no receptor cells are located there. (p. 238)

sensory interaction:

the principle that one sense may influence another, as when the smell of food influences its taste. (p. 259)

Weber's law:

the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount). (p. 234)

sensation:

the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment. (p. 230)

accommodation:

the process by which the eye's lens changes shape to focus near or far objects on the retina. (p. 237)

perception:

the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events. (p. 230)

parallel processing:

the processing of many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision. Contrasts with the step-by-step (serial) processing of most computers and of conscious problem solving. (p. 242)

vestibular sense:

the sense of body movement and position, including the sense of balance. (p. 254)

audition:

the sense or act of hearing. (p. 245)

parapsychology:

the study of paranormal phenomena, including ESP and psychokinesis. (p. 282)

psychophysics:

the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them. (p. 231)

kinesthesis: [kin-ehs-THEE-sehs]

the system for sensing the position and movement of individual body parts. (p. 254)

opponent-process theory:

the theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green. (p. 244)

Young-Helmholtz trichromatic (three-color) theory:

the theory that the retina contains three different color receptors—one most sensitive to red, one to green, one to blue—which, when stimulated in combination, can produce the perception of any color. (p. 244)

gate-control theory:

the theory that the spinal cord contains a neurological "gate" that blocks pain signals or allows them to pass on to the brain. The "gate" is opened by the activity of pain signals traveling up small nerve fibers and is closed by activity in larger fibers or by information coming from the brain. (p. 255)

lens:

the transparent structure behind the pupil that changes shape to help focus images on the retina. (p. 237)

5. The waveform of a sound determines our experience of:

timbre

2. The theory that humans have receptors in the retina that are specialized for red, blue, and green light is called the ________ theory.

trichromatic

1. The hue (or color) of light depends on its:

wavelength

What does research on sensory restriction and restored vision reveal about the effects of experience

People who were born blind but regained sight after surgery lack the experience to recognize shapes, forms, and complete faces. Animals who have had severely restricted visual input suffer enduring visual handicaps when their visual exposure is returned to normal. There is a critical period for some aspects of sensory and perceptual development. Without early stimulation, the brain's neural organization does not develop normally.

human factors psychology:

a branch of psychology that explores how people and machines interact and how machines and physical environments can be made safe and easy to use. (p. 280)

3. The central focal point in the retina where cones are heavily concentrated is known as the

d. fovea.

sensorineural hearing loss:

hearing loss caused by damage to the cochlea's receptor cells or to the auditory nerves; also called nerve deafness. (p. 250)

conduction hearing loss:

hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea. (p. 250)