CHAPTER 8: SENSATION AND

PERCEPTION

Did you do anything AWESOME this weekend?! Explain..

Of your five senses, which do you find to be most important?

If you had to lose one, either seeing or hearing, which would you rather keep and why?

List the five senses 1-5, 1 being the most important or necessary, and 5 being the least important.

JOURNAL #1

Objectives

Describe the field of study known as psychophysics.

Define and discuss threshold, Weber ’s law, and signal detection.

8.1

8.1 Sensation

• A sensation occurs anytime a stimulus activates one of your receptors.

• Any aspect of or change in the environment to which an organism responds is called a stimulus.

• Ex.- light turn on/ off, alarm clock, hand touch

• A stimulus can be measured in many physical ways, including its size, duration, intensity, or wavelength.

8.1- SENSATION

• A sensation can be combined with other sensations and your past experiences to yield a perception.

• Psychophysics—the study of the relationship between sensory experiences and the physical stimuli that causes them.

FIGURE 1

Fraser’s SpiralFraser’s spiral illustrates the difference between sensation and perception. Our perception of this figure is that of a spiral, but it is actually an illusion. Trace a circle carefully. Your finger will always come back to its starting point.

8.1

• Psychologists conduct experiments to determine the absolute threshold of the senses.

• Absolute threshold- Weakest amount of a stimulus required to produce a sensation, detected 50% of the time

8.1

• The absolute threshold for the five senses is as follows:

– Vision—seeing a candle flame 30 miles away on a clear night.

– Hearing—hearing a watch ticking 20 feet away.

– Taste—tasting 1 teaspoon of sugar dissolved in 2 gallons of water.

– Smell—smelling 1 drop of perfume in a 3-room house.

– Touch—feeling a bee’s wing falling a distance of 1 centimeter onto your cheek.

8.1

The Human SensesThis chart lists the fundamental features that make up the human sensory system.

8.1

• The difference threshold is the smallest change in a physical stimulus that can be detected between two stimuli half the time.

• Ex.- shine two lights and detect which is brighter

• The just noticeable difference (JND) refers to the smallest increase or decrease in the intensity of a stimulus that a person is able to detect half the time.

8.1

• A particular sensory experience depends more on the changes in the stimulus than on the absolute size or amount.

• Weber’s law: the larger or stronger a stimulus, the larger the change required for a person to notice that anything has happened to it.

• Ex.- backpack full of oranges

8.1

• Our senses have an ability to adapt, or adjust themselves, to a constant level of stimulation sensory adaptation

• They get used to a new level and respond only to deviations from it.

Answer the following questions What does psychophysics study?

What is a sensation?

What is a perception?

Explain the difference between absolute threshold and difference threshold.

What is Webster’s law?

How can our bodies use sensory adaptation?

ON THE BACK OF YOUR LAB

It 's easy to make a model of the eardrum (also called the "tympanic membrane") and see how sound travels through the air. Just stretch a piece of plastic wrap over a large bowl or pot (any container with a wide opening wil l work). Make sure the plastic wrap is stretched tightly over the container. The plastic represents the eardrum. Place about 20-30 grains of uncooked rice on the top of the plastic wrap. Now you need a noise maker. A tin cookie sheet or baking tray works well. Hold the cookie sheet close to the plastic wrap. Hit the cookie sheet to create a "big bang" noise and watch the rice grains jump.

The "big bang" produces sound waves (changes in air pressure) that cause the plastic sheet to vibrate which causes the rice grains to move. Sound waves vibrate the eardrum in much the same way.

Materials: Plastic wrap Container with wide opening Uncooked rice (any other small grain wil l work) Tin cookie sheet (or other noise maker)

8.2- The senses

8.1

The Disappearing CircleSensation depends on change and contrast in the environment. Hold your hand over one eye and stare at the dot in the middle of the circle on the right. You should have no trouble maintaining the image of the circle. If you do the same with the circle on the left, however, the image will fade. The gradual change from light to dark does not provide enough contrast to keep the visual receptors in your eye firing at a steady rate. The circle reappears only if you close and reopen your eye or you shift your gaze to the X.

FIGURE 4

The Stroop EffectTry to name the colors of the boxes in a as fast as you can. Then try to read the words in b as fast as you can. Finally, try to name the colors of the words in b as fast as you can. You probably proceeded more slowly when naming the colors in b.

SECTION 2-OBJECTIVES

• Describe the nature and function of the sense organs.

• Identify the skin and body senses and explain how they work.

Define the following words Pupil Lens Retina Optic Nerve

Label the human eyeLabel the human ear

PAGE 215- 220 IN YOUR BOOK

SECTION 2Vision

• How does vision occur?

– Light enters the eye through the pupil and reaches the lens, which focuses light on the retina.

– The retina contains two types of light-sensitive receptor cells, or photoreceptors: rods and cones.

The Human Eye

SECTION 2Vision (cont.)

– Rods: sensitive to much lower levels of light and are the basis for night vision.

– Cones: work best in the daylight and are sensitive to color.

–When some or all of a person’s cones do not function properly, he or she is said to be color deficient.

– These create impulses, that travel along the optic nerve to the brain, where they are routed to the occipital lobe.

COLOR BLIND TEST

FIGURE 5

The Human EyeThis cross section of the human eye shows the passage of light. Note that the retina receives an inverted image.

BLIND SPOT TEST

instructions.

SECTION 2

• Binocular fusion—the process of combining the images received from the two eyes into a single, fused image.

Vision (cont.)

• There is a difference between the images on the retinas, called retinal disparity.

SECTION 2

• Nearsightedness—having an eyeball that is too long, which causes problems seeing objects that are distant.

• Farsightedness—having an eyeball that is too short, which causes problems seeing up close.

Vision (cont.)

FIGURE 7

A Changing FlagStare steadily at the lowest right-hand star for about 45 seconds. Then stare at the blank space to the left. You should see a negative afterimage of this figure. This occurs because the receptors for green, black, and yellow become fatigued or neuronal firing rates shift, allowing the complementary colors of each to predominate when you stare at the white paper.

SECTION 2Hearing

• Hearing is caused by sound waves that pass through various bones until they reach the inner ear, which contains tiny hairlike cells that move back and forth.

• These hair cells change sound vibrations into neuronal signals that travel through the auditory nerve to the brain.

FIGURE 9

The Human EarThe earflap funnels sound waves down the ear canal to the eardrum. The bones of the middle ear pick up the vibrations and transmit them to the inner ear.

SECTION 2Hearing (cont.)

• The auditory nerve carries impulses from the inner ear to the brain, resulting in the perception of sound.

– Sound pressure energy is measured in decibels.

FIGURE 8

Decibel LevelsThe loudness of a second (its amplitude) is measured in decibels. Each increase of 10 decibels makes a sound 10 times louder. A normal conversation at 3 feet measures about 60 decibels, which is 10,000 times louder than a whisper of 20 decibels. Sound becomes painful at 130 decibels.

SECTION 2

• Two types of deafness:

– Conduction deafness- anything hinders physical motion through the outer or middle ear, or when bones in middle ear become ridged and cannot carry sound

– Hearing aid can help this by detecting sound waves

– Sensorineural deafness- occurs from damage to the cochlea, hair cells, or auditory neurons.

– Hearing aid can typically not help this, a cochlea implant possibly can

Hearing (cont.)

Do vision tests fi rst

10 QUESTIONS

SECTION 2

Balance

• The body’s sense of balance is regulated by the vestibular system inside the inner ear.

• Kinesthesis cooperates with the vestibular and visual senses to maintain posture and balance.

• muscles, tendons, and joints that send messages to the brain upon movement.

SECTION 2Smell and Taste

• Smell and taste are referred to as the chemical senses because their receptors are sensitive to chemical molecules.

• In order to smell, the appropriate gaseous molecules must come into contact with the smell receptors in your nose.

• These receptors send messages about smells through the olfactory nerve to the brain.

SECTION 2

Smell and Taste (cont.)

• Olfactory nerve—the nerve that carries smell impulses from the nose to the brain.

• In order to taste, appropriate liquid chemicals must stimulate receptors in the taste buds on your tongue.

• Taste information is relayed to the brain, along with data about the texture and temperature of the substance in your mouth.

SECTION 2

• Four primary sensory experiences—sour, salty, bitter, and sweet—make up taste.

• Smell plays a large role in taste.

• The combination of taste, smell, and tactile sensations is known as flavor.

The Human Tongue

FIGURE 10

The Human TongueWhen you chew, chemicals of the food mix with saliva and run down into trenches in your tongue. Once there, taste buds react to chemicals dissolved in saliva.

SECTION 2

The Skin Senses

• Receptors in the skin are responsible for sensing pressure, warmth, cold, and pain.

SECTION 2

The Skin Senses (cont.)

• There are two types of pain sensations:

– The sharp, localized pain you may feel immediately after an injury.

– The dull, generalized pain you may feel later.

SECTION 2

• Gate control theory of pain: we can lessen some pains by shifting our attention away from the pain impulses.

• This limits the number of impulses that can be transmitted, and can dull the pain.

The Skin Senses (cont.)

Can you trust your eyes?

THE STROOP TEST – PART 1

Say the name of the color of each square from left to right as quickly as you can.

3 VOLUNTEERS

STROOP TEST - PART 2

Say the name of the color of the following words as quickly as you can.

THE STROOP TEST – PART 3

Say the name of the color of the following words as quickly as you can – again.

8.3-

Listen to Sophie’s poem

Follow up to “The Eyes of Me”

What does the title of the documentary mean?What was the most surprising thing you saw or

learned in the documentary?What do you think would be most diffi cult about being

blind? What would you miss seeing the most?Which of the teenagers was most relatable to you?

Why? If you were blind, what would the eyes of you be?

JOURNAL #2

SECTION 3-OBJECTIVES

• Outline the principles involved in perception.

• Describe how we learn to perceive and what illusions are.

SECTION 3-POLLING QUESTION

Which of the following phone numbers are you more likely to remember?

A. 555-723-9927

B. 555748975

C. 5 5 5 8 84 98 74

D. 55-5879-5178

Perception- Brain receives information from the senses and organizes and interprets it into meaningful experiences

Perceptual thinking is essential for us to adapt to change

We don’t just see colors, hear noises, feel temps, etc., we see cars, buildings, hear voices, music, etc.

8.3- PERCEPTION

SECTION 3

Principles of Perceptual Organization• The brain makes sense of the world by

creating whole structures out of bits and pieces of information in the environment.

• Gestalt- whole is more important than the sum of its parts

SECTION 3

Principles of Perceptual Organization (cont.)

• Principles used in organizing patterns include:– Proximity-similar objects seen as a group

– Continuity- We see continuous patterns, not disrupted ones

– Similarity-similar and dissimilar objects mixed up, we see in groups

– Simplicity - We see the most simple shapes possible

– Closure- familiar patterns appear, even when pieces are missing

FIGURE 11

Gestalt PrinciplesHumans see patterns and groupings in their environment rather than disorganized arrays of bits and pieces.

SECTION 3

Figure-Ground Perception

• Figure-ground perception is the ability to discriminate properly between a figure and its background.

• It is applicable to both sight and hearing.

FIGURE 12

What Is It?What did you see the first time you looked at this illustration—a vase or two profiles? People invariably organize their experience into figure and ground.

SECTION 3

Perceptual Inference

• Perceptual inference—filling in the gaps based on past experiences with our senses.

O Iny srmat people can raed tihs.Cdnuolt blveiee that I cluod aulacity uesdnatnrd what I was Rdanieg. The phaonmneal pweor of the hmuan mnid, aoccdrnig to a rscheearch at Cmabrigde Uinervtisy.It deosn’t mttaer in what oredr the ltteers in a word are, the olny iprmoatnt tihng is that the frist and lsat ltteer be in the rghit pclae.The rset can be a taotl mses and you can still raed it wouthit a porbelm.This is bcuseae the huamn mnid deos not raed ervey lteter by istlef,But the word as a wlohe. Amzanig huh? Yaeh and I awlyas tghuhot slpelingwas ipmorantt!

SECTION 3

Learning to Perceive

• An active involvement in one’s environment is important for accurate perception.

• We must learn to perceive.

• This learning process is influenced by our needs, beliefs, and expectations.

• Perceptual set—the idea that we see what we want to see.

• Ex.- old lady and wallet

FIGURE 14

The Necker CubeThe Necker cube is an ambiguous figure. You can will yourself to see it as if you were looking down on it, with corner X closest to you, or as if you were looking up at it, with corner Y closest to you.

FIGURE 13

Pop-Out FeaturesReality is a jumble of sensations and details. The letter P probably pops out to you. The Qs may also pop out, but not as much as the P. You may not have noticed the O, though.

SECTION 3

Learning to Perceive (cont.)

• Subliminal messages- brief auditory or visual messages that are presented below the absolute threshold

• Subliminal perception—the ability to notice stimuli that affect only the unconscious mind.

• Ex.- Movie theater and coke sales

SECTION 3

Depth Perception

• Depth perception is the ability to recognize distances and three-dimensionality.

• Develops during infancy

• Monocular depth cue—a cue that can be used with a single eye to perceive distance and depth.

Monocular cues

8.3

SECTION 3

Depth Perception (cont.)

• Monocular depth clues include:– Relative height

– Interposition- overlapping images

– Light and shadows

– Texture-density gradient- farther an object is, less detail we see

– Motion parallax- apparent movement of stationary objects relative to one another

– Linear perspective

SECTION 3

Depth Perception (cont.)

• Binocular depth cue—a cue that depends upon the existence or movement of both eyes.

SECTION 3

Depth Perception (cont.)

• Binocular depth cues include:

– Convergence- eyes turn inward to see close object

– Retinal disparity- two images into one

SECTION 3

Constancy• Constancy is the tendency to perceive

certain objects in the same way regardless of changing angle, distance, or lighting.

Shape ConstancyWe perceive the opening door as being rectangular in shape, although our view of the shape of it changes as it opens.

SECTION 3

• Illusions are incorrect perceptions that are created when perceptual cues are distorted.

FIGURE 16

Lines of Different Lengths?The lines between the arrowheads in (a) are exactly the same length, as are the heavy black lines in (b). Some psychologists believe that the reason the lines in (a) seem of different lengths is because they are interpreted as offering different cues to their distance from the viewer. The lines in (b) may appear to be different in length because the brain interprets this diagram as though it is from a scene such as that in (c).

SECTION 3

Extrasensory Perception

• Extrasensory perception (ESP) includes the following four types:

– Clairvoyance-perceiving objects with no sensory input

– Telepathy- Reading someone’s mind or transferring thoughts

– Psychokinesis- moving objects through mental effort

– Precognition- Ability to foretell events