ap psychology page 1 of 12 exploration: sensation study...

AP Psychology of 12 Exploration: Sensation Study Guide

____________ © Copyright 2002 Apex Learning, Inc. All rights reserved. This material is intended for the exclusive use of registered users only. No portion of these materials may be reproduced or redistributed in any form without the express written permission of Apex Learning, Inc.

Summary In this study sheet you'll learn about the important mechanisms of the sensory organs and how each functions to produce a sensation. Before you start this section, review the following terms. You should be able to fully define each term. sensation psychophysics receptor cells transduction absolute threshold difference threshold sensory adaptation signal detection theory Vision Vision is the primary way most of us gather information about our environment�the other senses complement and provide additional or supporting information. In this next section, you'll learn about the properties of light, the structures and functions of the eye, and how information is processed in the eye. The Properties of Light Light is a form of electromagnetic radiation. In other words, it's a form of energy that radiates as electrical and magnetic waves. As a student of psychology, it's not necessary to know everything there is to know about electromagnetism. But you do need to know that electromagnetic radiation can be thought of as waves. These waves have amplitude ("height"), wavelength (distance between "peaks"), and frequencies (the number of waves in that pass in one second). Shorter waves have higher frequencies. Visible light (what the human eye can see) is but one small part of a spectrum of electromagnetic wavelengths that includes microwaves, X-rays, and radio waves. The visible light portion of the spectrum is called the visible spectrum and it goes from red (the longest waves and lowest frequencies) all the way to violet (the shortest waves and highest frequencies). Ultraviolet (beyond violet) wavelengths are too short for your eyes to detect, and infrared (below red) wavelengths are too long for your eyes to detect. Eye Structure and Function In this section, we'll focus on the structures of the eye that detect the raw energy: light. The human eyeball is globe-shaped and measures about one inch in diameter. Light waves enter the eye through the cornea. The cornea is the tough, transparent, protective layer that covers the front of the eye. It's about the size of a dime and its function is to bend the light waves that enter through the pupil.



The pupil is nothing but a hole! It's the black dark opening in the center of the iris. The iris is the colored part of your eye. It's composed of muscles that change the size of the pupil and change the amount of light entering the eyeball. When you enter a dark room, your pupil dilates (the iris makes itself narrower/makes the pupil larger) to allow as much light as possible to enter. When you're in a bright, well-lit room, the iris closes down (makes itself wider/makes the pupil smaller) and limits the amount of light that enters the pupil. Once the light passes through the pupil, it goes to the lens. The lens is a transparent, elastic, disc-shaped structure. The lens of the eye is like that of a camera: It bends light waves to focus an image onto another surface, in this case the back of your eye (the retina). If you're viewing an object some distance away from you, the lens becomes elongated and flat in order to focus the image as sharply as possible on the retina. If you're viewing an object close to you the lens becomes thick and more curved. This flattening and curving of the lens is called accommodation. As you age, the lens loses some of its elasticity, and your eyes lose the ability to change shape to accommodate for near vision (causing a condition called presbyopia). Other abnormalities of the lens may interfere with the placement of the image onto the retina. For example, if you're nearsighted (myopic), the lights rays are focused in front of the retina, causing distant objects to appear blurred. If you're farsighted (hyperopic), light is focused on a point beyond the retina, causing near objects to appear blurred. The retina processes light that is focused upon it by the lens. The retina contains several layers of cells that include the sensory receptors for vision. The most important layer is composed of light-sensitive photoreceptor cells: the rods and cones. In this layer, light is changed from a raw stimulus into electrochemical nerve impulses, a process known as transduction. After transduction of the light stimulus by the retina, the resulting electrical energy goes to the next layer of cells called bipolar cells. From the bipolar cells, electrochemical energy is transferred to the ganglion cell layer or the retina. The ganglion cells make up the optic nerve, which carries information received by the receptor cells to the brain. Rods and Cones When you look directly at an object, the image is focused on the fovea. The fovea is located in the retina. It is a small pit filled with "cones," which are responsible for your sharpest vision. Each eye contains more than 6 million cones.

pupil

iris

lens

retina

optic nerve

cornea

pupil

iris

lens

retina

optic nerve

corneafovea

pupil

iris

lens

retina

optic nerve

cornea

pupil

iris

lens

retina

optic nerve

corneafovea



Cones allow you to see color and fine details, but they don't function in the dark. So when you enter a dark room the rods take over. Rods detect black, white, and gray, and they are also responsible for your peripheral (sideways) vision. Each eye has more than 120 million rods. Dark Adaptation and Light Adaptation Let's say you and your friends plan to see a movie. You arrive a few minutes late and you enter the darkened movie theater. Your iris immediately begins to dilate to allow as much light as possible to enter the pupil. At first, you have difficulty finding your friends because you can't see them. You remember that your best friend is wearing a red jacket and light blue pants, but that doesn't help because even your own red jacket looks black! This is because your cones have shut off and your rods, which have taken over in the dark, have no color detectors. After a few minutes in the dark, your eyes begin to adapt (dark adaptation) and you can see where you're going. Complete dark adaptation takes about 20 to 30 minutes. After the movie, you and your friends decide to go to an outdoor café for dinner. When you open the exit doors to the parking lot, the afternoon sun seems extremely bright. In fact, the light momentarily blinds you. Immediately, the rods are shut off and the iris contracts to limit the amount of light passing through to the pupil. The cones are turned on (light adaptation), and you're now ready to look for your green car. Now you're driving along on the freeway. You want to pass the car in front you, so you look in your side-view mirror to make sure your left side is clear. You also turn your head slightly to make sure there isn't a car in your blind spot. Your blind spot is located on the retina wall where the blood vessels and nerve pathways enter and exit the eyeball. Also leaving each eye at the blind spot is the optic nerve, which is composed of a million ganglion cells. The optic nerve from each eye comes together at the optic chiasma. At this junction, the nerve fibers cross over to the opposite side of the brain. This crossover of impulses allows the brain to process two sets of signals from an image, which helps you perceive objects in three dimensions. From the optic chiasma, the optic nerve travels to the thalamus. There it connects with other neurons that transmit impulses to the primary visual cortex (occipital lobe). A great deal of information processing occurs in the retina before the visual signals are sent to the brain. However, this information is useless until it's processed in the brain. The primary visual cortex in the brain is responsible for analyzing information from the fovea. Some neurons in the this area respond only to specific features such as right angles, light, movement, texture, and color. These specialized neurons are called feature detectors. Color Color plays an important role in how the world looks. However, color doesn't exist in the world outside of our minds. Color is a psychological experience, created when specialized cells process wavelength information about light as it bounces off an object. Two major theories have been offered to explain color perception. The trichromatic theory states that there are three types of cones in the retina. Each responds to one of three colors: blue, green, and red. The proponents of this theory (Young and Helmholtz) demonstrated that mixing these three colors in different combinations could yield the full spectrum of colors we're capable of perceiving.



The second theory, the opponent-process theory, was first proposed by Ewald Hering. Like Young and Helmholtz, Hering proposed a three-color system, but added that each cell is sensitive to two opposing colors, such as blue and yellow, red and green, black and white. When a cell is responding to one color, its less able to respond to its opposite. So when the yellow/blue cells have an increased response to yellow, they have a decreased response to blue. If the cell is responding it's less able to respond to YELLOW� to BLUE.

Yellow Blue The black and white combination increases the cells' response rate for white light and decreases it in the absence of light. Afterimage Effect If you're viewing this document in color, take a couple of minutes to do an interesting experiment. Stare at the white dot in the image below for 60 seconds. Keep your eyes as still as possible the whole time. After 60 seconds have passed, look away at a white surface and watch the afterimage form. What do you see? Here's what happened, according to opponent process theory: The cells that are responsive to green and black became tired as you stared at the image. Then when you looked at the white surface, only the red part of the green/red cells fired, and only the white part of the black/white cells fired. Today researchers have discovered that color vision occurs in two stages (duplicity theory) and that both traditional theories have a biological basis. The first stage of processing occurs in the retina's red, green, and blue cones that respond to different color stimuli, as Young and Helmholtz suggested. The second stage of processing occurs when cells in the retina and the visual cortex respond in opposite ways to red versus green and blue versus yellow. Hearing In this section you'll learn about the properties of sound, the structures and functions of the ear, and how sound waves are processed to enable hearing. Sound waves Sound is the movement of air molecules in a wave pattern. Sound is produced whenever there is a rapid change in air pressure caused by vibrating objects, such as violin strings or vocal cords. Sound has three psychological characteristics: pitch, loudness, and timbre.



Pitch and loudness are associated with the physical attributes frequency and amplitude, respectively. Frequency refers to the number of complete changes in air pressure occurring during a given unit of time. Frequency is measured in hertz (Hz). One Hz equals 1 cycle per second. You perceive sound as either a high or a low level of pitch, which is determined by its frequency. For example, the faster a violin string vibrates the higher the pitch. Amplitude of the sound wave determines the intensity or loudness of the sound. Amplitude is the energy of a sound wave, and it's measured in decibels (dB). A normal conversation has amplitude of about 60 dB. Sounds above 120 dB, such as the sound of a jet taking off, are uncomfortably loud and even painful. Timbre refers to the quality or complexity of a sound (the specific mixture of amplitudes and frequencies of which it consists). Ear Anatomy and Function The ear has three major parts: the outer ear, the middle ear, and the inner ear. The outer ear is composed of the pinna (the part you can see on the side of someone's head), the auditory canal, and the eardrum. Outer Ear The outer ear is responsible for gathering and funneling the external stimuli (sound) into the auditory canal, or ear canal. The auditory canal is a one-inch long, tube-like structure lined with hairs (cilia). At the end of the auditory canal is the eardrum, or tympanic membrane. It's a thin, flexible membrane about 1/3 inch in diameter. When sound waves hit the eardrum, it vibrates. This vibration then triggers activity in the middle ear. Middle Ear The middle ear consists of three very tiny bones, the malleus (hammer), the incus (anvil), and the stapes (stirrup). The bones of the middle ear are collectively called the ossicles, and they connect the eardrum to the oval window, a membrane on the inner ear. The stapes presses on the oval window causing it to vibrate. Inner Ear The movement of the oval window causes waves in the fluid that fills the cochlea, a snail-shaped, bony chamber. The movement of the fluid sets in motion the basilar membrane that lines the cochlea. Attached to the basilar membrane are the hearing receptors or hair cells (cilia). As the waves travel through the cochlea, the hair cells bend. At this point,

ear canal

cochlea

eustacean tube

eardrumauditory nerve

stapes inner ear

middle ear

outer ear ear canal

cochlea

eustacean tube

eardrumauditory nerve

stapes inner ear

middle ear

outer ear



transduction occurs. Transduction is the process by which physical energy (sound) becomes an electrochemical impulse transmitted via the auditory nerve to the midbrain (thalamus) and to the auditory cortex. Theories of Hearing Hearing theories fall into two major classes: place theories and frequency theories. Place theories suggest that different parts of the basilar membrane vibrate to different pitches. The perception of pitch occurs when a particular spot or place on the basilar membrane of the cochlea vibrates and stimulates different hair cells. In contrast, frequency theories claim that the perception of pitch corresponds to the rate or frequency at which the entire basilar membrane vibrates. The brain detects the signal at the rate at which the auditory nerve fires. Dual Theories Today researchers have developed theories of auditory processing that combine the best of both place and frequency theories. For example, some researchers believe that frequency theory best explains how we perceive low frequencies and place theory best explains how we perceive other frequencies. Routing of Sensory Information in the Brain The brain is so complex that it's rarely correct to say that sensory signals go to one place to be processed. However, certain parts of the brain play larger roles than others in processing impulses from certain senses. Nerve impulses for hearing, taste, vision, and touch are routed to the thalamus, which then routes the information to the cerebral cortex for higher-level processing and also to the hindbrain where the signals are linked to emotional responses. Information from the nose, balance, and vestibular sense organs go directly to the hindbrain and to the cerebral cortex without being routed through the thalamus. In the cerebral cortex, visual information is processed in the occipital lobes at the back of the brain just above the cerebellum. Hearing information is processed in the auditory cortex in each temporal lobe. Information from smell and taste receptors are also processed in the temporal lobes, although a great deal of processing also occurs in hindbrain areas such as the limbic system. Touch signals are processed in the sensory motor cortex, which is across the top of both hemispheres of the cerebral cortex. Balance and vestibular signals are also processed in the sensory motor cortex, although the cerebellum also plays a big role.



Summary of Sensory Mechanisms In introductory psychology, you should have a basic understanding how each sense organ works. In other words, you should understand how it accomplishes transduction. Below is a table of all the concepts and terms you should know about each sense. If you're not familiar with any of these, look them up in your textbook or in one of the Web resources listed below the table. NOTE: Though it's a good idea to understand some of the details of how each sense organ works, it's more important to have a good understanding of the concepts of signal detection and perception so you can apply that understanding to any of the five senses. Don't focus so much on the details of each sense that you lose sight of the larger concepts that underlie theories about all of the senses.

Sensory Receptor

Source of Stimulation Anatomy of Function Major Processing Theory

Eyes (Vision)

Light from the electromagnetic spectrum Light waves vary in: length, height, and range

Cornea: Pupil Iris Lens Retina: Rods Cones

1. Duplicity theory of vision 2. Trichromatic theory (color vision) 3. Opponent process theory (color vision)

Ears (Audition)

Sound waves from changes in the air pressure caused by vibrating objects Sound waves vary in: length, height, and range

Outer ear: Pinna Auditory canal Eardrum Middle ear: Malleus Incus Staples Esutachian tube Inner ear: Oval window Cochlea Cilia Organ of corti

1. Place theory 2. Frequency theory

Nose (Olfaction)

Chemical molecules in the air

Nasal cavity: Olfactory Epithelium Olfactory bulb

Lock and key theory of olfaction



Sensory Receptor

Source of Stimulation Anatomy of Function Major Processing Theory

Tongue (Gustation)

Chemical molecules that trigger sweet, salty, or sour taste

Papillae or taste buds Lock and key theory of gustation

Skin (Pressure,

temperature, and

pain)

Pressure, temperature, and pain

Receptors in the skin for pressure, temperature, and pain Scientists believe that there are probably specific receptors for each type or sensory experience. Most receptors are located where the body is most sensitive (fingertips, lips, etc.)

The neuromatrix theory (pain)

Kinethesis (Body posture

and body movement)

Body posture and orientation

Receptors located in muscles, joints, and tendons

Vestibular (Sense of balance or

equilibrium)

Gravity and three-dimensional space

Inner Ear Semicircular canals Vestibular sacs (cilia)

Useful Web Sites These pages include a lot of useful information about how vision and hearing works. Vision:

http://www.stlukeseye.com/anatomy.asp http://faculty.washington.edu/chudler/bigeye.html

Hearing:

http://www.augie.edu/perry/ear/ear.htm http://faculty.washington.edu/chudler/bigear.html

Dianna Mertz

Rectangle



Check your Understanding 1. Rods and Cones are located in the_________. 2. Head rotation is sensed via_________. 3. Information from the muscles, tendons and joints provide sensory information about

__________. 4. The oval window and cochlea are located in the _________. 5. Information from the papillae provides information about __________.

6. Light is the physical energy source needed for__________.

7. Sound waves are the physical energy source needed for_________.

8. Chemical molecules in the air are the physical source of energy for__________.

9. Elastic structure that flattens and bulges is located in the__________. 10. Psychophysics studies the relationship between:

a. physical stimuli and our conscious experience of them. b. input from a sensory organ of different senses. c. sensory inputs and our level of psychological health. d. cultural experience and the perception of illusions. e. I'm not sure.

11. Which of the following is an example of transduction?

a. Sound waves in the air being slowed down in a different medium b. Electrical waves being translated into sound waves by a loudspeaker c. Light energy being converted into neural impulse by the retina d. Colored light is converted into white light e. I'm not sure.

12. You're shopping for a new car, and you've test-driven several models to determine

which have the best handling and performance. You learn that you can't tell the difference between models A and C. The difference between cars A and C is probably below your:

a. difference threshold. b. response bias. c. sensory adaptation. d. absolute threshold. e. I'm not sure.

13. The absolute threshold depends on:

a. the strength of the difference threshold. b. the neurophysiological hierarchy of modalities. c. the stimulus energy level required by the sensory system. d. the strength of the background noise. e. I'm not sure.



14. The smell of your mother's fried chicken is more powerful when you first enter your house than when you have been there for some time because of:

a. the JND. b. sensory adaptation. c. perceptual set. d. feature detectors. e. I'm not sure.

15. Which approach to sensory thresholds is concerned with biases, such as experience and

expectation? a. Absolute thresholds b. Classical conditioning c. Difference threshold theory d. Signal detection theory e. I'm not sure.

16. Name the type of retinal cell that helps you see in daylight. 17. Name the type of retinal cell that helps you see at night. 18. Contemporary research supports the trichromatic theory because of the discovery of

specialized_________? 19. What part of the retina is responsible for visual acuity and fine details? 20. Higher visual processing takes place in the________. 21. What type of photoreceptor cell is located on the edges of the retina?



Parts of the Eye Name each of the following parts of the eye and point to its location. See the section above (on vision) for answers. 22. The dark opening in the center of the eye. 23. The portion of the eye on which an image is

focused. 24. The colored circular portion of the eye. 25. Light first enters the light through the

___________. 26. Camera-like structure that changes shape to

help you see objects in the distance or close-up.

27. Where transduction occurs. 28. Carries the neural impulse to the visual

cortex.



Answers

1. retina

2. semicircular canals

3. kinethesis

4. inner ear

5. taste

6. vision

7. hearing

8. olfaction or smell

9. eye

10. a

11. c

12. a

13. c

14. b

15. d

16. cones

17. rods

18. cones

19. fovea

20. visual cortex

21. rods

ap psychology page 1 of 12 exploration: sensation study...

Documents