1 Vocabulary –perception –psychophysics –absolute threshold –Weber’s law –signal-detection theory –sensation Section 1-2 Reader’s Guide (cont.)

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Vocabulary

– perception

– psychophysics

– absolute threshold

– Weber’s law

– signal-detection theory

– sensation

Section 1-2

Reader’s Guide (cont.)

Click the Speaker button to listen to Exploring

Psychology.

Click the mouse button or press the Space Bar to display the information. Section 1 begins on page 207 of your textbook.

Blindfold Activity

• Blindfold Activity– Walk around school

with a partner– Hear, Smell, Taste,

Touch– How do our other

senses overcompensate?

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Section 1-4

Click the mouse button or press the Space Bar to display the information.

• The world is filled with physical changes.

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

• An alarm, an electric light, and an aching muscle are all stimuli for human beings.

What Is Sensation?

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Section 1-5


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

sensationwhat occurs when a stimulus activates a receptor

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

What Is Sensation? (cont.)

• The sense organs detect physical changes in energy such as heat, light, sound, and physical pressure.

• Sensory Deprivation– This tank allows

users to escape gravity

– Helps recover from strenuous activity

– Too much sensory deprivation can lead to loss of IQ

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Section 1-6


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

perceptionthe organization of sensory information into meaningful experiences

• A perception is the organization of sensory information into meaningful experiences.


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Figure -1-1

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 the circle carefully. Your finger will always come back to its starting point.

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Section 1-7

• What is the relationship between color and wavelength?

psychophysicsthe study of the relationships between sensory experiences and the physical stimuli that cause them

• How does changing a light’s intensity affect your perception of its brightness?



• The psychological study of such questions is called psychophysics.

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Section 1-8


• How much of a stimulus is needed to notice?

absolute thresholdthe weakest amount of a stimulus that a person can detect half the time

• Experiments can detect the absolute threshold–the weakest amount of a stimulus required to produce a sensation.

Threshold

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Figure 1-2

The Human Senses

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Section 1-9

• Another type of threshold is the difference threshold.

difference thresholdthe smallest change in a physical stimulus that can be detected between two stimuli

• The difference threshold refers to the minimum amount of difference a person can detect between two stimuli.

• A related concept is the just noticeable difference, or JND.

Sensory Differences and Ratios

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Section 1-10


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

Weber’s lawthe principle that the larger or stronger a stimulus, the larger the change required for an observer to notice a difference

• By experimenting with variations in sounds, temperatures, pressures, colors, tastes, and smells, psychologists are learning more about how each sense responds to stimulation.

Sensory Differences and Ratios (cont.)

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Section 1-11


• People who can detect minute changes in sensation are called experts.

• Experts who can detect small differences work as food tasters, wine tasters, smell experts, perfume experts, and so on.

Sensory Differences and Ratios (cont.)

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Section 1-12


• What happens whenyou eat a ton of HOT CHEETOS

• Senses are most responsive to increases and decreases, and to new events rather than to ongoing, unchanging stimulation.

• A good example of this sensory adaptation is the increase in visual sensitivity that you experience after a short time in a darkened movie theater.

Sensory Adaptation

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Section 1-13


• Sensory adaptation allows us to notice differences in sensations and react to the challenges of different or changing stimuli.

• This principle is helpful when performing many activities, such as the work of police, security guards, and home inspectors.

• These people may notice minute changes and act appropriately.

Sensory Adaptation (cont.)

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Figure 1-3

The Disappearing Circle

Sensation 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 circle reappears only if you close and reopen your eye or you shift your gaze to the X.

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Section 1-14


• There is no sharp boundary between stimuli that you can perceive and stimuli you cannot perceive.

signal-detection theorythe study of people’s tendencies to make correct judgments in detecting the presence of stimuli

• The signal-detection theory studies the relations between motivation, sensitivity, and decision making in detecting the presence or absence of a stimulus (Green & Swets, 1966).

Signal-Detection Theory

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Section 1-15


• Detection thresholds involve recognizing some stimulus against a background of competing stimuli.

• In studying the difficulties faced by radar operators, psychologists have reformulated the concept of absolute threshold to take into account the many factors that affect detection of minimal stimuli.

• As a result, signal-detection theory abandons the idea that there is a single true absolute threshold for a stimulus.

Signal-Detection Theory (cont.)

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Name the color of the squares.

Figure 1-4a

The Stroop Effect

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Name the color of the words in the figure below.

Figure 1-4b

The Stroop Effect (cont.)

Why was it more difficult to name the color of the words?

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Section 1-Assessment 1

Section Assessment

Review the Vocabulary What is the difference between sensation and perception?

A sensation is the activation of a sensory receptor by a stimulus. A perception is the organization of sensation into meaningful experiences.

Click the mouse button or press the Space Bar to display the answer.

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Section 1-Assessment 4

Section Assessment (cont.)

Think Critically Why do you think we do not respond to all stimuli present in our environment?

We do not respond to all stimuli present in our environment because our bodies would be overloaded with stimuli. Our bodies would soon be unable to process more sensory information.

Click the mouse button or press the Space Bar to display the answer.

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Section 1-Assessment Close

Section Assessment (cont.)

What would happen if you asked a four-year-old child who knew his colors but could not read to complete the Stroop effect activity? What if you tried this experiment with someone who did not speak English? What if you used noncolor words?

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1 Vocabulary –perception –psychophysics –absolute threshold –Weber’s law –signal-detection theory –sensation Section 1-2 Reader’s Guide (cont.)