AP Psych – Duez LEARNING TARGETS - Chapter 4 "Sensation & Perception"

If you learn only 4 things from this chapter for the AP Test...1. Perception is the interpretation of sensory information; it relies on experience.2. The difference between sensation and perception3. The structure and function of the eye4. The structure and function of the ear

Sensation and perception are areas that have been of interest topsychologists for most of the history of psychology. As we sit here, oursenses receive literally thousands of messages. We need to make senseof this information. Our senses take in the information, and they doso from birth. Yet the interpretive part -perception- requiresknowledge.

In this chapter, we will discuss the first two senses and thenhow those senses pass the raw data on to the perceptual processes wehave developed over time.

English physicist Sir Isaac Newton, in an experiment, observed that a ray of sunlight, or white light, was broken upinto the brilliant colors of the spectrum when it passed through a glass prism. He then noticed that the ray recombined intowhite light when it was beamed back through another prism. It occurred to Newton that since light rays are notcolored, color must not be an actual physical quality in the world. He concluded that color must exist onlyin the mind and not in nature.

If color does not actually exist in the world around us, then where do colors come from? To answer this question, wewill need to understand how our visual sensory system translates different wavelengths of light into neural impulses so thatour brain can interpret the information it receives as the sensation of color.

The other types of sensation we experience - such as sound, smell, taste, touch, and pain - are also products of the brain’sresponse to various kinds of sensory stimuli. But, typically two main types of systems are described when discussingsensation: vision & hearing. They are the most powerful ways that humans experience their world.

● How do we convert light into images?● How does the ear responds to sound waves?● How do we taste or smell?● How does the somatic sensory system function?

1. Psychophysics: Basic Concepts and Issues in Measuring PerceptionOne key to understanding perception is the accurate measurement of the processes of perception. Psychologists have workedhard to develop strategies for measuring perception. The concepts are not nearly as clear as other concepts in psychology, butlet’s address some of these measurement techniques.

How is stimulus intensity related to absolute thresholds?How does Just Noticeable Difference JND fit with Weber/Fechner's Laws?Central Idea of signal-detection?Practical significance of subliminal perception, sensory adaptation, and possible evolutionary

significance?

Psychophysicists use a variety of methods to relate sensory inputs to subjective perception. Thresholds are limits of yourperception. The absolute threshold is the least amount of information for our ability to perceive a stimulus. Adifference threshold is similar to absolute in that it is the amount of stimulus needed to determine a change in astimulus.

Absolute thresholds are not really absolute.Weber's law states that the size of a JND is a constant proportion of the size of the initial stimulus.

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AP Psych – Duez LEARNING TARGETS - Chapter 4 "Sensation & Perception"

Fechner's law states that larger and larger increases in stimulus intensity are required to produce JND in themagnitude of sensation.

Signal-detection theory = the detection of sensory inputs is influenced by noise in the system & bydecision-making strategies. It replaces Fechner's sharp threshold w/ detect ability & emphasizes that factorsbesides stimulus intensity influence detect ability.

Signal-Detection Theory addresses how participants are able to perceive information from the world. It argues that there iseither a detected stimulus (a hit), a miss, a correct rejection, or a false positive. A participant is presented with a variety ofstimuli, and each judgement is recorded. Good ability to detect results in more hits than misses and more correct rejectionsthan false positives.

2. Our Sense of Sight: The Visual SystemWhat are the 3 properties of light?What do the lens, pupil, rods and cones do?How do visual receptive fields function?How are visual signals routed from the eye to the primary cortex?

Light varies in terms of wavelength, amplitude, & purity.Light enters the eye through the cornea (part of the eye responsible for bending light) & pupil & is focused upside down

on the retina by the lens.The pupil is very important for vision. The pupil changes size depending on the amount of ambient light present. If there is a

lot of ambient light, the pupil constricts to limit the amount of light coming in. If there is a lot of surrounding darkness, thepupil dilates to allow in as much ambient light as possible.

The lens is just behind the pupil. The lens works in conjunction with the cornea to bend light so that it falls on theappropriate space in the rear of the eye.

White part of the eye = sclera. It is filled with blood vessels to provide nutrients to the eye. In addition, the sclera providesstructure to the eye.

Nearsighted = Distant objects appear blurry.Farsighted = Close objects appear blurry.Retina = neural tissues in eye, absorb light, process images, & send visual signals to the brain. It is the structure most

responsible for visual acuity. The retina stretches across the back half of the eye, with a differential distribution of types ofcells across the structure.

Rods & Cones are two types of photoreceptor cells that directly receive light stimulation.Cones (in fovea or center of the retina) key role in daylight vision and color perception.Rods (greatest density just outside of fovea) - critical to night & peripheral vision. Dark/Light adaptation involve changes in

the retina's sensitivity to light - allowing the eye to adapt to changes in illumination.Retina - transforms light into neural impulses & send info to brain through optic nerve. Receptive fields are areas in retina

that affect the firing of visual cells. Optic nerves from the inside 1/2 of each eye cross at the optic chiasm & then projectto the opposite side of the brain.

Bipolar cells in the first layer translate the information from rods and cones back out to the ganglion cells. Ganglion cellsthen transfer the information down toward the optic nerve. The point where the optic nerve exits the eye is a blind spot.You cannot see anything because there are no photo-receptors at the point at which those cells exit the retina.

The information is carried down the optic nerve, where it undergoes additional processing. Color information is added at thethalamus. At the end of the optic nerve is the occipital lobe, the structure most responsible for visual processing.

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AP Psych – Duez LEARNING TARGETS - Chapter 4 "Sensation & Perception"

How are additive & subtractive color mixing different?How have trichromatic & opponent process theories been reconciled to explain color vision?Difference between top-down & bottom-up processing?What is Gestalt psychology & Gestalt principles of form perception?How do perceptual hypotheses contribute to form perception?

Perceptions of color (hue) are primarily a function of light wavelength, while amplitude affects brightness & purityaffects saturation. 2 types of color-mixing: additive & subtractive. Human color perception depends on processes thatresemble additive.

Trichromatic theory = people have 3 types of receptors sensitive to red, green & blue.The opponent process theory = color perception depends on receptors that make antagonistic responses to red vs green,

blue vs yellow, & black vs white. The evidence now suggests that both theories are necessary.Reversible figures & perceptual sets demonstrate that the same visual input can result in very different perceptions.

According to feature analysis theories, people detect specific elements in stimuli & build them into recognizable formsthrough bottom-up processing. However, form perception also involves top-down processing, which progressesfrom the whole to the elements.

Gestalt psychology emphasized that the whole may be greater than the sum of its parts (features), as illustrated by Gestaltprinciples of form perception (figure-ground, proximity, similarity, closure, & simplicity).

What are some binocular and monocular depth cues?Are there cultural differences in depth perception?Why do hills look steeper than they are? What are perceptual constancies?What do optical illusions reveal about perceptual processes?Are there cultural disparities in susceptibility to illusions?

Binocular cues such as retinal disparity & convergence can contribute to depth perception (depends primarily onmonocular cues - texture gradient, linear perspective, light & shadow, interposition, relative size, & height in plane).

Conscious perceptions of geographical slant (visual & verbal estimates of pitch), tend to be greatly exaggerated.Haptic (tactile) judgments seem largely immune to this perceptual bias. Perceptual constancies in vision help viewersdeal with ever-shifting nature of proximal stimuli. A proximal stimuli is one that is received and transformed by theperceiver, while the distal stimulus is the stimulus in the environment. We do not have direct access to information in theworld. Rather, we use what our senses gather to make sense of the world. We use the information gathered from the distalstimulus to generate the proximal stimulus so that we have a representation of the world.

Optical illusions demonstrate that perceptual hypotheses can be inaccurate & perceptions are not simple reflections ofobjective reality (research: Muller-Lyer & Ponzo illusions).

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AP Psych – Duez LEARNING TARGETS - Chapter 4 "Sensation & Perception"

3. Our Sense of Hearing: The Auditory SystemLike the visual system, the auditory system is a mechanical system designed to translate external stimuli into a code that isunderstandable by the brain. The mechanical process of audition is very interesting, and in many ways, it is amazing that itworks as well as it does. The main goal of the auditory system is to translate acoustic energy into sound. It does this bypassing sound waves down through the ear until specialized cells are able to translate this sound into code that isinterpretable.

Key properties of sound & relation to auditory perceptions?Key structures in the ear in processing sound?How were central ideas of place theory & frequency theory reconciled?How are cues used to locate sounds in space?

The first structure of the ear is the pinna, or external ear. The pinna is the part of the ear that we see. It is composed ofcartilage and fat deposits, serves to funnel sound into the ear. The pinna is not essential - if you don’t have one, you canstill hear - yet the pinna helps us determine the location of sound in space by providing us with a more efficient collection ofsound from the front than from the back.

Inside the pinna is the auditory canal. At about 2.5 centimeters in length, this canal is the longest depression in the skull. Itspurpose is to focus the sound waves toward the tympanic membrane or eardrum: a thin tissue stretched over a bone,vibrates in sympathy with the sound waves, creating a message of the same amplitude as the original sound waves.

Sound waves are physical features. Sound varies in terms of wavelength (frequency), amplitude, & purity. Mainly they areperceptions of pitch, loudness, & timbre. Human ear sensitive = 2000 & 4000 Hz. Brief exposure to 120+ decibels can bepainful & damaging.

Sound transmitted through external ear via air conduction to the middle ear, sound waves are then translated into vibration oftiny bones called ossicles (the malleus - or hammer, the incus - or anvil, and the stapes - or stirrup). These are thesmallest bones in the human body and they work together to move the sound from the tympanic membrane into the innerear. The bones vibrate in sympathy with the sound waves that are causing the tympanic membrane to vibrate. The bonesend at the beginning of the inner ear.

The inner ear is the location of the cochlea. The cochlea is fluid filled. Here fluid conduction vibrates hair cells along thebasilar membrane in the cochlea (hair cells are the receptors for hearing).

Place theory = pitch perception depends on where vibrations occur along the basilar membrane.Frequency theory = pitch perception depends on the rate at which the basilar membrane vibrates.Modern evidence = the theories are complementary rather than incompatible.Auditory localization involves locating the source of a sound in space. People pinpoint where sounds have come from by

comparing inter-ear differences in the intensity & timing of sounds.

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AP Psych – Duez LEARNING TARGETS - Chapter 4 "Sensation & Perception"

4. Our Chemical Sense: Taste and SmellWhat are some binocular & monocular depth cues?Where are the receptors for taste?How many basic tastes are there?How do people vary in taste sensitivity?Where are the receptors for smell?What are the primary odors?

Taste buds are sensitive to 4 basic tastes: sweet, sour, bitter, and salty. Distributed unevenly across the tongue.Taste preferences = learned & heavily influenced by cultural background. Flavor influenced by odor of food.Smell is a chemical sense. Chemical stimuli activate receptors lining the nasal passages = olfactory cilia. Most receptors

respond to multiple odors.

5. Our Sense of Touch: Sensory Systems in the Skin AND Our Other Senses (Kinesthetic & Vestibular)What are tactile & thermal data routed to the brain?Gate-control theory?What does kinesthetic system and vestibular system do/monitor?

Sensory receptors in the skin respond to pressure, temperature, & pain. Tactile localization depends on receptive fieldssimilar to those seen for vision. Some cells in the somotosensory cortex appear to function like feature detectors. There arenerve fibers that respond specifically to warmth and cold.

Pain signals are sent to the brain along two pathways that are characterized as fast & slow. The perception of painis highly subjective & may be influenced by mood, attention, and culture.

Gate-control theory holds that incoming pain signals can be blocked in the spinal cord.Endorphins and a descending neural pathway appear responsible for the suppression of pain in the central nervous

system.Kinesthetic system monitors the position of various body parts. Receptors in joints/muscles send signals to the brain along

the same pathways as tactile stimulation.

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AP Psych – Duez LEARNING TARGETS - Chapter 4 "Sensation & Perception"

Sense of balance is primarily dependent on activity in the semicircular canals in the vestibular system.

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AP Psych – Duez LEARNING TARGETS - Chapter 4 "Sensation & Perception"

REVIEW QUESTIONS:1. When physical energy is transformed into neural impulses, it is referred to as

(reception, transduction, perception, sensation, induction)2. An object as it appears in the world as a visual stimulus is referred to as

(distal stimulus, proximal stimulus, figure, ground, retinal image)3. ____ is receiving data from the external environment; ____ is how our brains make sense of that data.

(induction; reception … gestalt; detection … comprehension; transduction … perception; sensation … sensation;perception)

4. The amount of stimulus required to determine that a stimulus has changed just a little bit is called the(difference threshold, absolute threshold, just noticeable difference, just noticable threshold, taste aversion)

5. The part of the eye responsible for receiving photons of light and then translating them into neural messages is the(sclera, lens, cornea, pupil, retina)

6. The part of the ear responsible for translating information into neural impulses is the(pinna, cochlea, semicircular canals, tympanic membrane, incus)

7. The part of the retina in which there is no visual receptors is the point at which the optic nerve exists the eye. What is theterm for this point?

(rod, blind spot, cone, fovea, pupil)8. What is the term for the smallest amount of a sensation that is necessary for a person to actually notice that it is present?

(absolute threshold, difference threshold, perceptual set, perceptual adaption, sensory adaption)9. The part of the brain responsible for coding auditory information is the

(temporal lobe, occipital lobe, somatosensory cortex, frontal lobe, hypothalmus)10. The part of the brain responsible for coding visual information is the

(temporal lobe, somatosensory cortex, hypothalamus, occipital lobe, frontal lobe)11. The __ is the first structure involved in focusing photons of light.

(cornea, lens, retina, sclera, vitreous humor)12. In signal detection theory, when a participant responds that a stimulus was present and it was, the response is called a

(correct rejection, ROC curve, miss, hit, false positive)13. Gestalt principles are used to make order out of perceptions so that we see things as connected and not just random bits of

information. Which of these is NOT a common Gestalt principle?(Similarity, Localization, Closure, Proximity, Good continuation)

14. The structure in the eye that changes shape to accommodate the closeness or distance of an object is the(cornea, retina, lens, sclera, iris)

15. The structure in the ear that is responsible for gathering sound initially is the(pinna, tympanic membrane, cochlea, semicircular canals, stapes)

16. The receptor cells that make the ransduction for the auditory system are called the(basilar membrane, hair cells, cochlea, semicircular canals, stapes)

17. The cells responsible for coding for color in the eyes are the(rods, iris, cones, retina, fovea)

18. The point of the focus for the eye that contains mostly cones is the(rods, iris, cones, retina, fovea)

19. Which part of our auditory system is best able to aid us in the localization of sounds?(Ossicles, Pinna, Tympanic membrane, Occipital lobe, Eardrum)

20. The structure that contains the main receptor cells in the auditory system is the(semicircular canals, tympanic membrane, pinna, malleus, cochlea)

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