Chapter 4 SENSATION AND PERCEPTION

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Chapter 4SENSATION AND PERCEPTION

• Section 1 Sensation and Perception The Basics
• Section 2 Vision
• Section 3 Hearing
• Section 4 Other Senses
• Section 5 Perception

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Question In what ways do sensation and
perception contribute to an understanding of our
environment?
Section 1 Sensation and Perception The Basics

• SENSATION AND PERCEPTION CONTRIBUTE TO AN
  UNDERSTANDING OF OUR ENVIRONMENT
• Sensation provides information to the central
  nervous system about the physical environment
• Perception is the process through which people
  interpret sensory stimulation

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Section 1 Sensation and Perception The Basics

• Sensationthe stimulation of sensory receptors
  and the transmission of sensory information to
  the central nervous system (the spinal cord and
  brain).
• The stimulation of the senses is automatic
• Perceptionthe psychological process through
  which we interpret sensory stimulation.
• Perception reflects learning, expectations, and
  attitudes.
• Stimulation of the senses and the ways in whi9ch
  people interpret that stimulation are affected by
  several concepts, These concepts include
  absolute threshold, difference threshold,
  signal-detection theory and sensory adaptation.

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Absolute Threshold
Section 1 Sensation and Perception The Basics

• When you have your hearing tested you must sit in
  a booth or quiet room with earphones on your
  ears. You hear nothing at first but then
  suddenly you hear a beep. This is your absolute
  threshold for hearing.
• Prior to hearing that beep the tester was trying
  different beeps but you just did not hear them.
  The one you heard was the weakest one you were
  capable of hearing.
• Dogs can hear certain sounds that the human ear
  can not hear.
• Absolute thresholds have been determined for the
  senses of vision, hearing, smell, taste, and
  touch.
• These absolute thresholds vary from person to
  person.

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Difference Threshold
Section 1 Sensation and Perception The Basics

• Difference thresholdthe minimum amount of
  difference that can be detected between two
  stimuli.
• For example someone shows you two dark blue paint
  chips. You may think they are the same color,
  even if they are slightly different.
• Now imagine that one of the paint chips is
  removed and replaced with another chip that is
  just a bit lighter or darker.
• The smallest amount of difference you can see in
  order to distinguish between the two shades of
  blue is your difference threshold.

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Signal-Detection Theory
Section 1 Sensation and Perception The Basics

• Signal-detection theorya method of
  distinguishing sensory stimuli that takes into
  account not only their strengths but also such
  elements as the setting, your physical state,
  your mood, and your attitudes.
• Signal-detection theory considers psychological
  factors such as motivations, expectations, and
  learning.
• We focus on whatever we consider important and
  shut out everything else.

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Sensory Adaptation
Section 1 Sensation and Perception The Basics

• Sensory adaptationthe process by which we become
  more sensitive to weak stimuli and less sensitive
  to unchanging stimuli.
• For example, city dwellers adapt to the sounds of
  traffic (unchanging stimuli) except for the
  occasional car backfire or fire engine siren.
• At the movies, Marc, Linda and Todd could see the
  people around them betterthe people were weak
  stimuli.

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Homework Practice Online
Section 1 Sensation and Perception The Basics

• Go to http//go.hrw.com
• Type in SY 7 Ch 4
• Complete Section 1 of Homework Practice Online
• Remember to print your answer sheet

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Light

• No other sense allows us to gather so much
  information from nearby and distant sources.
• To understand vision, is important to know how
  light works and how our eyes function.
• Light is electromagnetic energy and is described
  in wavelengths.
• The light humans can see makes up only a small
  part of the spectrum of electromagnetic energy.
• Sunlight can also be broken down into colors by
  means of a glass structure called a prism.
• The main colors of the spectrum from longest to
  shortest wavelengths are Red, Orange, Yellow,
  Green, Blue, Indigo and Violet (Roy G. Biv)

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Homework Practice Online

• Go to http//go.hrw.com
• Type in SY 7 Ch 4
• Complete Section 2 of Homework Practice Online
• Remember to print your answer sheet

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Question How does the eye enable vision?
Section 2 Vision

• THE EYE AND VISION
• Light enters the eye and then is projected onto a
  surface
• The amount of light that enters the eye is
  determined by the size of the pupil which adjusts
  automatically to the amount of light entering the
  eye.
• Pupil size is also sensitive to our emotions
• We can be literally wide-eyed with fear meaning
  that the pupils open widely when we are afraid.
• Once light enters the eye, it encounters the lens
  which adjusts to the distance of objects by
  changing its thickness

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Question How does the eye enable vision?
Section 2 Vision

• These changes project a clear image of the object
  onto the retina, which consists of neurons that
  are sensitive to the light called photoreceptors
• Once the light hits the photoreceptors, a nerve
  carries the visual input into the brain where the
  information is relayed to the visual area of the
  occipital lobe

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The Blind Spot
Section 2 Vision

• Look at Figure 4.3 and find the point where the
  optic nerve leaves the eye. When light hits that
  point, the eye registers nothing because that
  area lacks photoreceptors or the blind spot.
• We all have one. If we did not have one we would
  never be able to see anythingno visual input
  would reach the brain through the optic nerve for
  interpretation.

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Rods and Cones
Section 2 Vision

• Two kinds of photoreceptorsrods and cones.
• Rodsare sensitive only to the brightness of
  light. They allow us to see in black and white.
• Cones provide color vision.

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Dark and Light Adaptation
Section 2 Vision

• When you first enter a movie theater, it may be
  too dark for you to find a seat. As time passes,
  you come to see the seats and the other people
  more clearly. This adjustment to lower lighting
  is called dark adaptation.
• Your ability to see in low light continues to
  improve for up to 45 minutes.
• Adaptation to bright light happens much more
  quickly than adaptation to the dark ( one to two
  minutes).

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Visual Acuity
Section 2 Vision

• Visual acuitythe sharpness of vision.
• It is determined by the ability to see visual
  details in normal light.
• Nearsightedyou would have to be particularly
  close to an object to make out its details.
• A person standing 20 feet from the Snellen Chart
  and can only read the T or the E would have a
  vision of 20/100.
• Farsightedyou need to be farther away from an
  object than a person with normal vision to see it
  clearly

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Color Vision
Section 2 Vision

• People with normal color vision see any color in
  the spectrum of visible light.
• Dogs and cats see far fewer colors than humans.
• Insects, birds, fish and reptiles experience a
  wide variety of colors.

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The Color Circle
Section 2 Vision

• Complete the color circle activity
• It is the colors of the spectrum bent into a
  circle.
• The colors across from each other are called
  complementary.
• This is not pigment color but light

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Cones and Color Vision
Section 2 Vision

• Cones enable us to perceive color.
• Some are sensitive to blue, some to green, and
  some to red
• For example, the images you see on a television
  screen actually consist of thousands of very
  small dots called pixels. Each is either blue,
  green or red
• Other colors are created from various
  combinations of blue, green and red

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Afterimages
Section 2 Vision

• Look at the strangely colored flag in Figure 4.5
  for at least half a minute. Then look at a white
  sheet of paper. What do you see?
• You should see a flag composed of the familiar
  red, white and blue. This is an afterimage.

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Color Blindness
Section 2 Vision

• If you can see the colors of the visible spectrum
  you have normal color vision.
• People who are partially or totally unable to
  distinguish color due to an absence of or
  malfunction in the cones.
• Partial color blindness is fairly common. These
  individuals see some colors but not others.
• Figure 4.6 shows one of the types of tests that
  are used to check for color blindness.

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Eye Diagram
Section 2 Vision
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Homework Practice Online

• Go to http//go.hrw.com
• Type in SY 7 Ch 4
• Complete Section 2 of Homework Practice Online
• Remember to print your answer sheet

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Question How does the ear perceive sound?
Section 3 Hearing

• Sound travels through the air in waves
• Caused by changes in air pressure that result
  from vibration.
• Each of these vibrations is called a cycle or a
  sound wave.
• Every sound has its own pitch and loudness
• Sound enters the outer ear and is funneled to the
  eardrum
• Inside the middle ear, the hammer, anvil, and
  stirrup vibrate, transmitting the sound to the
  inner ear
• Within the brain, auditory input is projected
  onto the hearing areas of the cerebral cortex

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Pitch
Section 3 Hearing

• Sound waves can be very fast, occurring many
  times per second.
• The pitch of a sound depends on it frequency or
  the number of cycles per second.
• The more cycles per second, the higher the
  pitch of a sound.
• The human ear can hear sound waves that vary from
  20 to 20,000 cycles per second.
• Dogs and dolphins hear sounds well beyond 20,000
  cycles per second

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Loudness
Section 3 Hearing

• Loudness is determined by the height or
  amplitude of sound waves.
• The loudness of a sound is measured in decibels,
  a unit that is abbreviated dB
• Zero dB is considered the threshold of hearing
• Zero dB is about as loud as the ticking of a
  watch 20 feet away in a very quiet room

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The Ear
Section 3 Hearing

• The ear is the instrument for sensing all the
  sounds around us.
• We have an outer ear, middle ear and an inner ear
• The ear drum is the gateway from the outer ear to
  the middle ear.
• It vibrates when sound waves strike it.
• Sound waves are transmitted to three small bones
  in the middle ear ( the hammer, the anvil and the
  stirrup).
• The inner ear consist of the cochlea Greek for
  snail
• The cochlea is a bony tube that contains fluids
  as well as neurons that move in response to the
  vibrations of the fluids.
• The movement generates neural impulses that are
  transmitted to the brain via the auditory nerve.

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Deafness
Section 3 Hearing

• Deafness can be inherited or caused by disease,
  injury or old age.
• Conducive deafness occurs because of damage to
  the middle ear.
• People with conducive deafness are often helped
  by hearing aids.
• Hearing aids provide the amplification that the
  middle ear does not.

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Deafness

• Sensorineural Deafness is caused by damage to the
  inner ear.
• Neurons in the cochlea are destroyed
• Sensorineural deafness is due to damage to the
  auditory nerve, either through disease or through
  prolonged exposure to very loud sounds.
• People who go to high-volume rock concerts and
  leave, with a ringing sensation in your ears,
  means you have destroyed neurons in your ear.

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Ear Diagram
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Homework Practice Online

• Go to http//go.hrw.com
• Type in SY 7 Ch 4
• Complete Section 3 of Homework Practice Online
• Remember to print your answer sheet

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Question What are the chemical, skin, and body
senses?
Section 4 Other Senses

• CHEMICAL, SKIN, AND BODY SENSES
• Smell allows a person to taste
• If your sense of smell were not working, an onion
  and an apple would taste very much alike to you
• Odors are detected by receptor neurons high in
  each nostril
• The receptors send information about the odors to
  the brain via the olfactory nerve
• One odor can also be masked by another which is
  how air fresheners work.

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Taste
Section 4 Other Senses

• Taste sweetness, sourness, saltiness,
  bitterness, and umami (meaty or savory)
• Dogs can taste sweetness but cats cannot.
• The flavor of a food is more complex than taste
  alone.
• Flavor depends on odor, texture, and temperature
  as well as taste
• For example apples and onions taste similar but
  their flavors differ greatly
• Taste is sensed through receptor neurons located
  on taste buds on the tongue.
• Sensitivities to different tastes can be
  inherited
• Taste cells reproduce rapidly enough to
  completely renew themselves in a week.
• The taste system is one of the most resilient of
  all the bodys sensory systems
• It is very rare for anyone to suffer a complete
  permanent taste loss.

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The Skin Senses--Touch
Section 4 Other Senses

• Touch is a combination of pressure, temperature,
  and pain
• Example Premature infants grow more quickly and
  stay healthier if they are touched
• Older people seem to do better if they have a dog
  or cat to stroke and cuddle.
• Sensory receptors located around the roots of
  hair cells fire where the kin is touched.
• Different parts of the body are more sensitive to
  pressure than others.
• The fingertips, lips, nose, and cheeks are more
  sensitive than the shoulders, thighs and calves.

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Touch--Temperature
Section 4 Other Senses

• Normal body temperature is 98.6F
• The receptors for temperature are neurons just
  beneath the skin
• Example When you first jump into a swimming
  pool, the water may seem cold. Yet, after a few
  moments the water feels warmer as your body
  adjusts to it.

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Senses--Pain
Section 4 Other Senses

• Headaches, backaches, tootaches are only a few of
  the types of pain most of us experience from time
  to time.
• More serious health problems such as arthritis,
  cancer, and wounds also cause pain.
• See figure 4.9 Distribution of Pain Receptors
• Pain originates at the point of contact
• Pain message to the spinal cord to the thalamus
  in the brain then to the cerebral cortex where
  the person registers the location and severity of
  the pain.
• Aspirin and ibuprofen are common pain-fighting
  drugs that work by curbing production of
  prostaglandins.

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Gate Theory
Section 4 Other Senses

• Gate theory suggests that only a certain amount
  of information can be processed by the nervous
  system at a time.
• Rubbing or scratching the area transmits
  sensations to the brain that compete with pain
  messages for attention. Many neurons cannot get
  their pain messages to the brain. The flooding
  prevents many or all of the calls from getting
  through.

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Body Senses--Vestibular and kinesthetic
Section 4 Other Senses

• Try this activity
• Stand up and close your eyes
• Do you have to look in a mirror to be certain
  that you are still upright? No
• Vestibular sense tells you whether you are
  physically upright without having to use your
  eyes.
• Sensory organs in you ears monitor your bodys
  motion and position in relation to gravity.
• It also tells you whether your body is changing
  speeds, such as in an accelerating automobile.

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Body Senses--Kinesthetic
Section 4 Other Senses

• Try this activity
• Close your eyes then touch your nose with your
  index fingers (right then left)
• How did you locate your nose with your eyes
  closed?
• Kinesthesis is the sense that informs people
  about the position and motion of their bodies.
• Sensory information is fed to the brain from
  sensory organs in the joints, tendons, and
  muscles.

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Homework Practice Online

• Go to http//go.hrw.com
• Type in SY 7 Ch 4
• Complete Section 4 of Homework Practice Online
• Remember to print your answer sheet

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Rules of Perceptual Organization
Section 5 Perception

• Perceptionthe way in which we organize or make
  sense of our sensory impressions.
• There are many different ways in which people
  make sense of sensory information.
• The rules of perceptual organization are closure,
  figure-ground perception, proximity, similarity,
  continuity, and common fate.

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LAWS OF SENSORY PERCEPTION
Section 5 Perception

• Gestalt psychologists apply the principle that
  the whole is more than the sum of the parts
• Gestalt psychologists refer to this as the
  principle of closure
• Closure the tendency to perceive a complete or
  whole figure even when there are gaps in what
  your senses tell you.
• Look at figure 4.10 What do you see?
• If you perceive the dog, it is not just because
  of the visual sensations provided by the drawing.
  
• It is because you are familiar with dogs and that
  you try to fit the pieces of information into a
  familiar pattern.

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LAWS OF SENSORY PERCEPTION (continued)

• Look at figure 4.11 What do you see?
• In the center of the drawing, you probably see a
  vase. Look again, can you see the two profiles
  that form the sides of the vase?
• Figure-ground perception the perception of a
  figure against a background.
• The vase was against a dark background, the
  profiles were against a light background.
• What we perceive as te figure and what we
  perceive as the background influences our
  perception.

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LAWS OF SENSORY PERCEPTION (continued)

• Look at Part A of figure 4.12
• If you saw 3 pairs of lines, you were influenced
  by the proximity, or nearness, of some of the
  lines to each other.
• Proximity the tendency to group together visual
  and auditory events that are near each other.
• Look at Part B of the figure, did you perceive it
  as a six-by-six grid or as three columns of xs
  and three columns of os?
• If you said xs and os then you were grouping
  according to the law of similarity.
• What about Part C? Again what do you see? If you
  saw the wavy line and the straight line, you were
  probably organizing your perceptions according to
  the rule of continuity.
• Finally there is the law of common fate. Have
  you ever noticed how when you see things moving
  together, you perceived them as belonging
  together? Example a group of people running in
  the same direction.

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Perception of Movement Stroboscopic Motion
Section 5 Perception

• To sense movement, humans need to see an object
  change its position relative to other objects.
• Psychologists study the illusions of movement or
  stroboscopic motion.
• Stroboscopic Motionis produced by showing the
  rapid progression of images or objects that are
  not moving at all.
• For example, a little book designed to be flipped
  through quickly so that the figures on the pages
  appear to be moving.
• Another example movies the audience is shown 16
  to 22 pictures or frames per second. Each frame
  is slightly different from the previous one.
• Perception smoothes over the interruptions and
  fills in the gaps.

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Depth Perception

• Depth means distance away
• Without thinking you decide how far away a glass
  of juice is from you then you decide to reach out
  to take it.
• Monocular Cuesneed only one eye to be perceived.
• Monocular cues cause certain objects to appear
  more distant from the viewer than others

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Monocular Cues

• Monocular cues include perspective, clearness,
  overlapping, shadow, and texture gradient.
• See page 95 column 2
• Perspectivethe tendency to see parallel lines as
  coming closer together, or converging as they
  more away from us.
• The clearness of an object helps in telling us
  how far away it might be.
• Overlapping tells us which objects are far away
  and which ones are near.
• Shadows and highlights give us information about
  objects three-dimensional shapes and where they
  are placed in relation to the source of light.
• Texture is the surface quality and appearance of
  an object. Texture that is farther away fro us
  appears to be denser than texture that is closer
  and we see less detail.
• Gradient is a progressive change

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Monocular Cues

• The most complex of monocular cues of depth is
  called motion parallax.
• Motion parallaxinvolves not a stationary picture
  but the image of something as the viewer moves.
• Motion parallax is the tendency of objects to
  seem to more forward or backward depending on how
  far away they are from the viewer.

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Binocular Cues for Depth

• Both eyes are required to perceive binocular cues
  for depth.
• Two types are retinal disparity and convergence
• Retinal disparitythe difference between the two
  images as an object that the retina receives as
  the object moves closer or farther away
• Convergenceis associated with feelings of
  tension in the eye muscle.

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Perceptual Constancies

• Perceptual constancies develop from experience.
• Each persons experience creates perceptual
  constancies of size, color, brightness, and
  shape.
• Size constancy is the tendency to perceive an
  object as being of one size no matter how far
  away the object is, even though the size of its
  image on the retina varies with its distance.
• Color constancyis the tendency to perceive
  objects as keeping their color even though
  different light might change the appearance of
  their color.

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Perceptual Constancies

• Brightness constancyis the tendency to perceive
  an object as being equally bright even when the
  intensity of the light around it changes.
• Shape Constancy is the knowledge that an item has
  only one shape no matter what angle you view that
  item from.

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Homework Practice Online

• Go to http//go.hrw.com
• Type in SY 7 Ch 4
• Complete Section 5 of Homework Practice Online
• Remember to print your answer sheet

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Question What are the five types of sensation?
Senses
Body Senses
Vision
Hearing
Smell
Touch
Taste