Sensation and Perception - Part V: Content Review for the AP Psychology Exam

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Sensation and Perception
Part V: Content Review for the AP Psychology Exam


To study sensation is to study the relationship between physical stimulation and its psychological effects. Sensation is the process of taking in information from the environment. Perception refers to the way in which we recognize, interpret, and organize our sensations.


In psychophysics, the branch of psychology that deals with the effects of physical stimuli on sensory response, researchers determine the smallest amount of sound, pressure, taste, or other stimuli that an individual can detect. Psychologists conducting this type of experiment are attempting to determine the absolute threshold—the minimal amount of stimulation needed to detect a stimulus and cause the neuron to fire 50 percent of the time. At the absolute threshold, we cannot detect lower levels of stimuli, but we can detect higher levels.

In a typical absolute-threshold experiment, an experimenter plays a series of tones of varying volume to determine at exactly what volume the participant first reports that she can hear the tone. Another approach to measuring detection thresholds involves signal detection theory (SDT). This theory takes into consideration that there are four possible outcomes on each trial in a detection experiment: the signal (stimulus) is either present or it is not, and the participants respond that they can detect a signal or they cannot. Therefore, we have the following four possibilities:

· Hit—the signal was present, and the participant reported sensing it.

· Miss—the signal was present, but the participant did not sense it.

· False alarm—the signal was absent, but the participant reported sensing it.

· Correct rejection—the signal was absent, and the participant did not report sensing it.

Weber’s Law

Ernst Weber (1795—1878) noticed that at low weights, say one ounce, it was easy to notice one-half-ounce increases or decreases in weight; however, at high weights, say 32 ounces, participants were not well able to judge one-half-ounce differences. The observation that the JND is a proportion of stimulus intensity is called Weber’s law. Simply put, this law states that the greater the magnitude of the stimulus, the larger the differences must be to be noticed.

SDT takes into account response bias, moods, feelings, and decision-making strategies that affect our likelihood of having a given response.

Another type of threshold is the discrimination threshold, which is point at which one can distinguish the difference between two stimuli. The minimum amount of distance between two stimuli that can be detected as distinct is called the just noticeable difference (JND) or difference threshold.

In this case, the experiment might involve playing pairs of tones of varying volumes. The participants would try to determine if the tones that they heard were the same or different.

That moment at the optometrist’s when they ask which is better — lens 1 or lens 2? Lens 1 or lens 2? — and you freak out because they seem the same. Don’t worry! You’re right at the JND!

Subliminal perception is a form of preconscious processing that occurs when we are presented with stimuli so rapidly that we are not consciously aware of them. When later presented with the same stimuli for a longer period of time, we recognize them more quickly than stimuli we were not subliminally exposed to. Clearly, there was some preconscious processing, known as priming, occurring even if we were not aware of it. Another example of preconscious information processing can be seen in the tip-of-the-tongue phenomenon, in which we try to recall something that we already know is available but is not easily available for conscious awareness. This phenomenon demonstrates that certain preconscious information may be available to the conscious mind but quite difficult to access.


Sensory organs have specialized cells, known as receptor cells, which are designed to detect specific types of energy. For example, the visual system has specialized receptor cells for detecting light waves. The area from which our receptor cells receive input is the receptive field. Incoming forms of energy to which our receptors are sensitive include mechanical (such as in touch), electromagnetic (such as in vision), and chemical (such as in taste). No matter what the form of the input at the level of the receptor, it must first be converted into the electrochemical form of communication used by the nervous system. Through a process called transduction, the receptors convert the input, or stimulus, into neural impulses, which are sent to the brain. For example, when we hear something, tiny receptor cells in the inner ear first convert mechanical vibrations into electrochemical signals. These signals are then carried by neurons to the brain. Transduction takes place at the level of the receptor cells, and then the neural message is passed to the nervous system. The incoming information from all of our senses, except for smell, travels to the sensory neurons of the thalamus. The thalamus, as you may recall from the neuroanatomy section, redirects this information to various sensory cortices in the cerebral cortex where it is processed. It is at the level of the thalamus that the contralateral shift occurs, in which much of the sensory input from one side of the body travels to the opposite side of the brain. Olfaction, or the sense of smell, travels in a more direct path to the cerebral cortex, without stopping at or being relayed by the thalamus.


Sensory receptors deal with a wide range of stimuli, and we experience a wide variety of input within each given sensory dimension. Imagine, for example, the gamut of colors and intensities that the eye can sense and relate to the brain. Sensory coding is the process by which receptors convey such a range of information to the brain. Every stimulus has two dimensions: what it is (its qualitative dimension) and how much of it there is (its quantitative dimension). The qualitative dimension is coded and expressed by which neurons are firing. For example, neurons firing in the occipital lobe would indicate that the sensory information is light, and neurons firing in the temporal lobe might indicate that the sensory stimulus is sound. In contrast, the quantitative information is coded by the number of cells firing. Bright lights and loud noises involve the excitation of more neurons than those brought on by dim lights and quiet noises. The wavelengths of light and frequency of sound are perceived as hue and pitch, respectively. The physical characteristic of amplitude is perceived as brightness for light and loudness for sound. Similarly, the physical trait of complexity is known as saturation, when dealing with light, and timbre, when referring to sound. Sensory neurons respond to differing environmental stimuli by altering their firing rate and the regularity of their firing pattern. Single-cell recording is a technique by which the firing rate and pattern of a single receptor cell can be measured in response to varying sensory input.

Visual Mechanisms

Sensation occurs in differing ways for the various sensory systems. Visual sensation occurs when the eye receives light input from the outside world. Note that the object as it exists in the environment is known as the distal stimulus, whereas the image of that object on the retina is called the proximal stimulus. Because of the shape of the retina and the positions of the cornea and the lens, the proximal stimulus is inverted. The brain, through perceptual processes, is then capable of interpreting this image correctly.


Visual sensation is a complex process. First, light passes through the cornea, which is a protective layer on the outside of the eye. Just under the cornea is the lens. The curvature of the lens changes to accommodate for distance. These changes are called, logically, accommodations. The retina is at the back of the eye and serves as the screen onto which the proximal stimulus is projected. The retina is covered with receptors known as rods and cones. Rods, located on the periphery of the retina, are sensitive in low light. Cones, concentrated in the center of the retina, or fovea, are sensitive to bright light and color vision. After light stimulates the receptors, this information passes through horizontal cells to bipolar and amacrine cells. Some low-level information processing may occur here. The stimulation then travels to the ganglion cells of the optic nerves. The optic nerves cross at the optic chiasm, sending half of the information from each visual field to the opposite side of the brain. Each visual field includes information from both the left and right eye. From here, information travels to the primary visual cortex areas for processing. The brain processes the information received from vision—color, movement, depth, and form—in parallel, not serial, fashion. In other words, the brain is simultaneously identifying the patterns of what is seen. Serial processing occurs when the brain computes information step-by-step in a methodical and linear matter, while parallel processing happens when the brain computes multiple pieces of information simultaneously. Over time and through practice, serial processes can turn into parallel processes, just as riding a bike initially requires a person to consider each decision, but later is done seemingly automatically. Feature detector neurons “see” different parts of the pattern, such as a line set at a specific angle to the background. Like pieces of a jigsaw puzzle, these parts are amalgamated to produce the pattern in the environment. This process starts at the back of the occipital lobe and moves forward. As the information moves forward, it becomes more complex and integrated. This process, by which information becomes more complex as it travels through the sensory system, is known as convergence and occurs across all sensory systems. Once lines and colors have been sensed, the information travels through two pathways: the dorsal stream and the ventral stream. The ventral stream is the “what” pathway that connects to the prefrontal cortex, allowing a person to recognize an object. The dorsal stream is the “where” pathway that integrates visual information with the other senses through a connection to the somatosensory cortex at the top of the brain.


Think C for cones and C for color.

Two different processes contribute to our ability to see in color. The first is based on the Young-Helmholtz or trichromatic theory. According to this theory, the cones in the retina of the eyes are activated by light waves associated with blue, red, and green. We see all colors by mixing these three, much as a television does. However, this does not tell the whole story. Another theory, known as opponent process theory, contends that cells within the thalamus respond to opponent pairs of receptor sets—namely, black/white, red/green, and blue/yellow. If one color of the set is activated, the other is essentially turned off. For example, when you stare at a red dot on a page and then you turn away to a blank piece of white paper, you will see a green dot on the blank piece of paper because the red receptors have become fatigued and, in comparison, the green receptors are now more active. This is known as an afterimage. Color blindness responds to this theory, as well.

Most color blindness occurs in males, which provides strong evidence that this is a sex-linked genetic condition. Dichromats are people who cannot distinguish along the red/green or blue/yellow continuums. Monochromats see only in shades of black and white (this is much more rare). Most color blindness is genetic.

Auditory Mechanisms

Auditory input, in the form of sound waves, enters the ear by passing through the outer ear, the part of the ear that is on the outside of your head, and into the ear canal.


Q: What are the ossicles?

Answer on this page.

The outer ear collects and magnifies sound waves. The vibrations then enter the middle ear, first vibrating the tympanic membrane. This membrane abuts the ossicles, the three tiny bones that comprise the middle ear. Vibration of the tympanic membrane vibrates the ossicles. The last of the three ossicles is the stapes, which vibrates against the oval window. The oval window is the beginning of the inner ear. The vibrations further jiggle the cochlea. Within the cochlea are receptor cells, known as hair cells, so named for their hair-like cilia which move in response to the vibrations. The hair cells line a structure in the cochlea called the basilar membrane. From the cochlea, sound energy is transferred to the auditory nerve and then to the temporal lobe of the auditory cortex. The inner ear is also responsible for balance and contains vestibular sacs, which have receptors sensitive to tilting.

Various theories have been suggested for how hearing occurs. Current thinking relies on the work of Georg von Békésy, which asserts that a traveling wave energizes the basilar membrane. As frequencies get higher, so do the peaks of the traveling wave, increasing the stimulation of the receptors for hearing. This accounts for recognition of sound above 150 Hz. However, humans can hear from 20 to 20,000 Hz. The volley principle—which states that receptor cells fire alternatively, increasing their firing capacity—appears to account for the reception of sound in the lower ranges. Place theory asserts that sound waves generate activity at different places along the basilar membrane. Frequency theory in hearing states that we sense pitch because the rate of neural impulses is equal to the frequency of a particular sound. Deafness can occur from damage to the ear structure or the neural pathway.

Conductive deafness refers to injury to the outer or middle ear structures, such as the eardrum. Impairment of some structure or structures from the cochlea to the auditory cortex results in sensorineural, or nerve, deafness.

Other Sensory Mechanisms

Olfaction (smell) is a chemical sense. Scent molecules reach the olfactory epithelium, deep in the nasal cavity. The scent molecules contact receptor cells at this location. Axons from these receptors project directly to the olfactory bulbs of the brain. From there, information travels to the olfactory cortex and the limbic system. Because the amygdala and hippocampus connect to olfactory nerves, it is easy to understand why certain smells trigger memories.

Gustation (taste) is also a chemical sense. The tongue is coated with small protrusions known as papillae. Located on the papillae are the taste buds, the receptors for gustatory information. There are five basic tastes: sweet, salty, bitter, sour, and umami (savory). These five tastes may have evolved for specific reasons. For example, sweetness, which we tend to like, is often accompanied by calories. Most poisonous plants, in contrast, taste bitter, a taste we generally do not like. Information from the taste buds travels to the medulla oblongata and then to the pons and the thalamus. This information is then relayed to the gustatory areas of the cerebral cortex, as well as the hypothalamus and limbic system.

The skin has cutaneous and tactile receptors that provide information about pressure, pain, and temperature. The receptor cells sensitive to pressure and movement are fast-conducting myelinated neurons, which send information to the spinal cord. From here, the information goes to the medulla oblongata, the thalamus, and finally, to the somatosensory cortex. Pain information is sent via two types of neurons; C fibers are unmyelinated and responsible for the throbbing sense of chronic pain, while myelinated A-delta fibers send information about acute pain. The pain signal first reaches the spinal cord and triggers the release of “substance P” (a neuropeptide, or chemical signal similar to a neurotransmitter, that alerts the spinal cord to the presence of a painful stimulus). The signal then travels to the thalamus and to the cingulate cortex, which is responsible for attention. Once pain is perceived, the brain begins to reduce the intensity of the signal through a process known as “pain-gating.” A signal is sent from the brain to opiate receptors in the spinal cord, which reduces the sensation of pain. This information projects to the limbic system and then to the somatosensory cortex. The receptor cells for temperature can be divided into cold fibers, which fire in response to cold stimuli, and warm fibers, which are sensitive to warm stimuli.

Other senses include the vestibular sense, which involves the sensation of balance. This sense is located in the semicircular canals of the inner ear. Kinesthesis, found in the joints and ligaments, transmits information about the location and position of the limbs and body parts.


Use this table to compare and contrast different sensory systems.


A: The ossicles are three tiny bones in the middle ear, called the malleus, incus, and stapes, that connect the eardrum to the oval window.


Our sensory systems need to do more than simply detect the presence and absence of stimulation. They also need to do more than detect the intensity or quality of stimuli. A key feature of our sensory systems is that they are dynamic, that is, they detect changes in stimuli intensity and quality. Two processes are used in responding to changing stimuli: adaptation and habituation.

Adaptation is an unconscious, temporary change in response to environmental stimuli. An example of this process is our adaptation to being in darkness. At first, it is difficult to see, but our visual system soon adapts to the lack of light. Sensory adaptation to differing stimuli leaves our sensory systems at various adaptation levels. The adaptation level is the new reference standard of stimulation against which new stimuli are judged. A familiar example is that of the swimming pool. If you enter a 75-degree swimming pool directly from an air-conditioned room, it will feel warm, as your adaptation level is set for the cold room. If, however, you are on a hot beach and then enter the same pool, it will feel cold, as your adaptation level is set for the heat of the beach.

Habituation is the process by which we become accustomed to a stimulus, and notice it less and less over time. Dishabituation occurs when a change in the stimulus, even a small change, causes us to notice it again. Dishabituation also occurs when a stimulus is removed and then re-presented. A good example of this pair of processes is in the noise from an air conditioner. We may notice a noisy air conditioner when we first enter a room, but after a few minutes, we barely even notice it; we have habituated to the noise. However, when the air conditioner’s compressor turns on, slightly altering the sound being generated, we once again notice the noise. This noticing is dishabituation. Although habituation is not typically a conscious process, we can control it under certain circumstances. If, in the examples above, we are unaware of the air-conditioner noise, but then someone asks us whether the noise of the air conditioner sounds like something else, we can force ourselves to dishabituate, and again notice the noise. This control over our information processing is the key to distinguishing habituation from sensory adaptation: you cannot control sensory adaptation; for example, you cannot force your eyes to adapt to darkness by mere force of will. You can, however, force yourself to pay attention to things to which you have habituated.


The term attention refers to the processing through cognition of a select portion of the massive amount of information incoming from the senses and contained in memory. In common terms, attention is what allows us to focus on one small aspect of our perceptual world, such as a conversation, while constantly being assailed by massive input to all of our sensory systems. Attention serves as a bottleneck, or funnel, that channels out some information in order to focus on other information. This process is essential because the brain is not equipped to process and pay attention to all of the information it is presented with at a particular moment. The fact that the brain must take shortcuts and focus on particular information is a key issue in perception, which explains why the brain can be tricked through illusions. A good example of attention in action is selective attention, by which we try to attend to one thing while ignoring another. For example, we try to attend to a movie, while trying to ignore the people having a conversation behind us. An example of selective attention is called the “cocktail party phenomenon,” which refers to our ability to carry on and follow a single conversation in a room full of conversations. At the same time, our attention can quickly be drawn to another conversation by key stimuli, such as someone saying our names. This recognition of our names is a demonstration that, although we are not paying very much attention to those other conversations, we are definitely attending to information we are not consciously aware of at that moment. This phenomenon has been studied in the laboratory with headphones, by playing a different message in each of a participant’s ears. The participant is instructed to repeat only one of the conversations. This repetition is referred to as shadowing. The message played into the nonshadowed ear is largely ignored, however. Changes in that message or key words, like names, can draw attention to that message. There are two main types of theories explaining selective attention: filter theories and attentional resource theories. Filter theories propose that stimuli must pass through some form of screen or filter to enter into attention. Donald Broadbent proposed a filter at the receptor level. However, the notion of a filter at this level has generally been discarded, based on findings showing that meaningful stimuli, such as our own names, can catch our attention. Therefore, the filter must be at a higher processing level than that of the receptors because meaning has already been processed.

Differentiating Messages

It is easiest for people to tell the difference between messages when they are physically different, such as when one message is spoken by a woman and the other by a man.

Attentional resource theories, in contrast, posit that we have only a fixed amount of attention, and this resource can be divided up as is required in a given situation. So, if you are deeply engrossed in this book, you are giving it nearly all of your attentional resources. Only strong stimulation could capture your attention. This theory is also inadequate, however, because all attention is not equal. For example, a conversation occurring near you is more likely to interfere with your reading than is some other nonverbal noise.

Divided attention, trying to focus on more than one task at a time, is most difficult when attending to two or more stimuli that activate the same sense, as in watching TV and reading. The ability to successfully divide attention declines with age.


When we were describing sensory mechanisms, we talked about how environmental stimuli affect the receptor systems. This section deals with perceptual processes—how our mind interprets these stimuli. There are two main theories of perception—bottom-up and top-down.

Bottom-up processing achieves recognition of an object by breaking it down into its component parts. It relies heavily on the sensory receptors. Bottom-up processing is the brain’s analysis and acknowledgement of the raw data. Top-down processing, by contrast, occurs when the brain labels a particular stimulus or experience. For example, let’s think about the first time a person tastes the sourness of a lemon. In this example, the neurons firing to alert the brain of the presence of some taste in the mouth is a bottom-up process, whereas labeling it “sour” is the top-down process. However, the next time the person sees a lemon, they might salivate or wince before ever tasting the lemon. This is top-down processing because the expectation based on experience influences the perception of the lemon.

Remember This!

Sensation = bottom-up process

Perception = top-down process

Visual perception is quite complex. We need to perceive depth, size, shape, and motion. Depth perception is facilitated by various perceptual cues. Because of the limited ability of the brain to process information, it must take certain shortcuts and educated guesses based on how the world is normally structured. As such, the brain uses these cues but can also fall victim to illusions.

Visual perception cues can be divided into monocular and binocular cues. Monocular depth cues are those that we need only one eye to see. As such, they can be depicted in two-dimensional representations. Relative size refers to the fact that images that are farther from us project a smaller image on the retina than do those that are closer to us. Therefore, we expect an object that appears much larger than another to be closer to us. Related to this idea is the idea of texture gradient. Textures, or the patterns of distribution of objects, appear to grow more dense as distance increases. If we are looking at pebbles in the distance, they appear smooth and uniform, but close up may appear jagged and rough. Another monocular depth cue is interposition, also known as occlusion, which occurs when a near object partially blocks the view of an object behind it. Linear perspective is a monocular cue based on the perception that parallel lines seem to draw closer together as the lines recede into the distance. Picture yourself standing on a train track, looking at the two rails. As the rails move away from you, they appear to draw closer together. The place where the rails seem to join is called the vanishing point. This is the point at which the two lines become indistinguishable from a single line and then disappear. Objects present near the vanishing point are assumed to be farther away than those along the tracks at a point where they diverge greatly. Aerial perspective, another perceptual cue, is based on the observation that atmospheric moisture and dust tend to obscure objects in the distance more than they do nearby objects. An example of this notion occurs when one is driving in the fog; a far-off building looks more distant than it really is through the fog, but its image quickly becomes clearer and clearer as you approach. Relative clarity is a perceptual clue that explains why less distinct, fuzzy images appear to be more distant. Motion parallax is the difference in the apparent movement of objects at different distances, when the observer is in motion. For example, when riding on a train, a person sees distant objects out of a window as seeming to move fairly slowly; they may appear to move in the same direction as the train. Nearer objects seem to move more quickly and in the opposite direction to the movement of the train. Note that motion parallax differs from other monocular depth cues in that it requires motion and cannot be represented in a two-dimensional image.

Binocular depth cues rely on both eyes viewing an image. They result from the fact that each eye sees a given image from a slightly different angle. Stereopsis refers to the three-dimensional image of the world resulting from binocular vision. Retinal convergence is a depth cue that results from the fact that your eyes must turn inward slightly to focus on near objects. The closer the object, the more the eyes must turn inward. The complement to stereopsis is binocular disparity, which results from the fact that the closer an object is, the less similar the information arriving at each eye will be. This process can be demonstrated by covering one eye, then the other, while looking at something directly in front of you. This procedure reveals two very different views of the object. Repeat this procedure with an object across the room, however, and the two views appear more similar.

Nature, Nurture, and the Visual Cliff

Together, the binocular cues for vision enable us to have depth perception. To test whether depth perception was innate (nature) or learned (nurture), researchers Eleanor Gibson and Richard Walk developed the visual cliff to test depth perception. The visual cliff was a glass tabletop that appeared to be clear on one side and had a checkerboard design visible on the other side. Infants were placed on the checkerboard side of the “cliff,” and researchers tracked whether they would crawl onto the clear side, thus going “over the cliff.” Most infants refused to do so, which implies that depth perception is at least partially innate. Because the infant had to be a few months old, it was unclear how much learning had influenced depth perception. With other animals tested (chicks, pigs, kittens, turtles), it was concluded that the animal’s visual skills depended on the importance of vision to the organism’s survival.

As previously stated, the visual system also needs to perceive and recognize form, that is, size and shape. The Gestalt approach to form perception is based on a top-down theory. This view holds that most perceptual stimuli can be broken down into figure-ground relationships. Figures are those things that stand out, whereas the ground is the field against which the figures stand out. The famous vase-face example shows us that figure and ground are often reversible.


Some basic Gestalt principles of figure detection include the following:

· Proximity—the tendency to see objects near each other as forming groups


· Similarity—the tendency to prefer grouping like objects together


· Symmetry—the tendency to perceive forms that make up mirror images


· Continuity—the tendency to perceive fluid or continuous forms, rather than jagged or irregular ones


· Closure—the tendency to see closed objects rather than those that are incomplete


These Gestalt principles represent the Law of Prägnanz, or minimum tendency, meaning that we tend to see objects in their simplest forms.

A different theory of form recognition is based on a feature detector approach. This approach differs from the Law of Prägnanz, which reduces an image to its simplest form, by positing that organisms respond to specific aspects of a particular stimulus. For example, when driving a car, we use feature detection to anticipate the movement of other cars and pedestrians that demand our immediate attention, helping us to be more aware of the environment.

Constancy is another important perceptual process. Constancy means that we know that a stimulus remains the same size, shape, brightness, weight, and/or volume even though it does not appear to. People who have never seen airplanes on the ground will have trouble perceiving the actual size of a plane because of their experience with the size of the object when airborne. The ability to achieve constancy, which is innate, and the experience, which is learned, both contribute to our development of the various types of constancy.

One of the most complex abilities we have is motion detection. We perceive motion through two processes. One records the changing position of an object as it moves across the retina. The other tracks how we move our heads to follow the stimulus. In both cases, the brain interprets the information with special motion detectors. A related issue is the perception of apparent motion. Examples of apparent movement include blinking lights on a roadside arrow, which give the appearance of movement (phi phenomenon); a motion picture, where still pictures move at a fast enough pace to imply movement (stroboscopic effect); and still light that appears to twinkle in darkness (autokinetic effect).






absolute threshold

detection thresholds

signal detection theory (SDT)



false alarm

correct rejection

discrimination threshold

just noticeable difference (JND) (difference threshold)

Ernst Weber

Weber’s law

subliminal perception


tip-of-the-tongue phenomenon

Receptor Processes

receptor cells

receptive field


contralateral shift

Sensory Mechanism

sensory coding

qualitative dimension

quantitative dimension

single-cell recording

visual sensation

distal stimulus

proximal stimulus








bipolar cells

amacrine cells

optic nerves

optic chiasm

serial processing

parallel processing

feature detector


Young-Helmholtz theory (trichromatic theory)

opponent process theory


color blindness



auditory input

tympanic membrane




vestibular sacs

place theory

frequency theory


conductive deafness

sensorineural deafness



cutaneous receptors

tactile receptors

cold fibers

warm fibers

vestibular sense


Sensory Adaptation






selective attention

cocktail party phenomenon


filter theories

attentional resource theories

divided attention

Perceptual Processes

perceptual processes

bottom-up processing

top-down processing

visual perception

monocular depth cues

relative size

texture gradient


linear perspective

vanishing point

aerial perspective

relative clarity

motion parallax

binocular depth cues


retinal convergence

binocular disparity

Eleanor Gibson and Richard Walk

visual cliff

Gestalt approach

top-down theory






Law of Prägnanz

feature detector approach


motion detection

apparent motion

phi phenomenon

stroboscopic effect

autokinetic effect

Chapter 9 Drill

See Chapter 19 for answers and explanations.

1.If a person is supposed to press a button when he sees a red triangle but instead presses the button when he sees a green triangle, what is this called?

(A)Opponent process


(C)False alarm


(E)Correct rejection

2.The five basic gustatory sensations that most animals possess are

(A)bitter, salty, sweet, tangy, sour

(B)salty, sweet, bitter, sour, umami

(C)smooth, grainy, cold, hot, prickly

(D)grain, fruit, meat, vegetable, dairy

(E)salty, sharp, umami, sour, bitter

3.Cats tend to notice slight movements under low lighting conditions with greater ease than do humans; they do not, however, find it easy to distinguish colors. This is primarily due to their retinas containing, in comparison to humans,

(A)relatively fewer amacrine cells and relatively more bipolar cells

(B)relatively fewer ganglion cells and relatively more osmoreceptors

(C)relatively fewer cilia and relatively more optic nerve cells

(D)relatively fewer cones and relatively more rods

(E)relatively fewer mechanoreceptors and relatively more ossicles

4.The Gestalt concept of perceptual continuity refers to

(A)our tendency to see objects near to each other as belonging to the same group

(B)our tendency to see objects that are closer to us as larger than objects that are farther away

(C)our tendency to see fluid or complete forms rather than irregular or incomplete ones

(D)our tendency to see similar-looking objects as part of the same group

(E)our tendency to see two slightly different images from each of our eyes

5.Which of the following would be the best illustration of Weber’s law?

(A)Most people can recognize the difference between a 40- and 80-decibel sound, but not an 80- and 82-decibel sound.

(B)A person can recognize an imperceptible amount of perfume in a ten-foot-by-ten-foot room.

(C)People cannot attend to more than one stimulus at a time.

(D)A person has the ability to tell the difference between a 20-watt bulb and a 100-watt bulb 50 percent of the time.

(E)All auditory stimuli above a certain frequency “sound” as if their frequencies are the same.

6.What structure in the middle ear generates vibrations that match the sound waves striking it?

(A)Basilar membrane

(B)Tympanic membrane




7.In the human visual pathway, what cell type comprises the bundle of fibers called the optic nerve?


(B)Bipolar cells

(C)Ganglion cells

(D)Fovea cells


8.In a given drawing, instead of perceiving a series of lines, humans perceive two shapes: a circle and a rectangle. What best accounts for this phenomenon?

(A)The principles of Gestalt psychology

(B)Bottom-up processing

(C)Parallel processing

(D)Weber’s law



9.Claire views the figure above and reports seeing a triangle in the center supported by some concentric discs. Which Gestalt principle does Claire rely on most heavily to render this description?






10.Laretta walks into a classroom and notices a strange odor. She sits down for class and, over time, forgets about the smell. When she returns to class the next day, she notices the odor again. This phenomenon is known as







Respond to the following questions:

· Which topics in this chapter do you hope to see on the multiple-choice section or essay?

· Which topics in this chapter do you hope not to see on the multiple-choice section or essay?

· Regarding any psychologists mentioned, can you pair the psychologists with their contributions to the field? Did they contribute significant experiments, theories, or both?

· Regarding any theories mentioned, can you distinguish between differing theories well enough to recognize them on the multiple-choice section? Can you distinguish them well enough to write a fluent essay on them?

· Regarding any figures given, if you were given a labeled figure from within this chapter, would you be able to give the significance of each part of the figure?

· Can you define the key terms at the end of the chapter?

· Which parts of the chapter will you review?

· Will you seek further help, outside of this book (such as a teacher, Princeton Review tutor, or AP Students), on any of the content in this chapter—and, if so, on what content?