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Module 1.6a

Why, then, if we stare at an object without flinching, does it not vanish from sight?
Because, unnoticed by us, our eyes are always moving. This continual flitting from one spot
to another ensures that stimulation of the eyes’ receptors continually changes (Figure 1.6-3). ENGAGE 1.6-3
(20 minutes) To demonstrate how
Figure 1.6-3
The jumpy eye intrusions of changing stimuli can
Our gaze jumps from one spot harm performance, divide students
to another every one-third of
a second or so. Eye-tracking into small groups. Then have one
equipment recorded a person’s
eye jumps while looking at this person in each group perform a simple
photograph of Edinburgh’s task that requires attention, such as
Princes Street Gardens
(Henderson, 2007). The circles completing a crossword puzzle or
represent visual fixations, and
the numbers indicate the time word find. Have the other members of
of fixation in milliseconds
(300 milliseconds = 3/10ths of a the group test how different types of
second). noise interference affect the person’s
ability to complete the task. They
© John M. Henderson should record their results. Have them
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
consider the following questions:
®
AP Science Practice
What if we actually could stop our eyes from moving? Would sights seem to vanish, • Does noise with words (reading
as odors do? To find out, psychologists have devised ingenious instruments that maintain Research a story) interfere more than noise
a constant image on the eye’s inner surface. Imagine that we have fitted a volunteer, Mary, The ability to track and measure without words (static or yelling
Copyright © Bedford, Freeman & Worth Publishers.
with such an instrument — a miniature projector mounted on a contact lens. When Mary’s eye movements helped advance
the field of visual sensation.
eye moves, the image from the projector moves as well. So everywhere that Mary looks, the Investigators are now able to “blah, blah”)?
scene is sure to go. Can you guess the weird result? (See Figure 1.6-4.) obtain concrete evidence of the
way our eyes naturally avoid • Does music with words interfere
sensory adaptation. It is often
more than music without words?
“Stabilized images on the retina,” by R. M. Pritchard. Copyright © 1961 Scientific American, Inc. All evolve. • How loud does the noise have to
advances in technology or
equipment that help theories
be for it to become distracting?
Rights Reserved.
®
(a) (b) AP Science Practice PRACTICE
Research Research Methods & Design
Figure 1.6-4 Remember that there are strict (SP 2)
Sensory adaptation: Now you see it, now you don’t! guidelines for the ethical treatment
of human participants. So while (5 minutes) Ask students if they
(a) A projector mounted on a contact lens makes the projected image move with the the study presented here might
eye. (b) Initially, the person sees the stabilized image. But thanks to sensory adaptation, seem uncomfortable, the volun- would volunteer to participate in
her eye soon becomes accustomed to the unchanging stimulus. Rather than the full teers provide informed consent.
image, she begins to see fragments fading and reappearing. the study depicted in Figure 1.6-4.
Why or why not? In the discus-
Although sensory adaptation reduces our sensitivity, it offers an important benefit: free- sion, review the ethical guidelines
dom to focus on informative changes in our environment. Technology companies under-
stand the attention-grabbing power of changing stimulation: Our phone’s notifications are described in Module 0.5.
hard to ignore. If we’re performing other tasks, these intrusions can harm our performance
(Stothart et al., 2015).
Sensation: Basic Concepts Module 1.6a 121

ENGAGE 1.6-3
03_myersAPpsychology4e_28116_ch01_002_163.indd 121 hold a mouthful of vinegar and water until it
15/12/23 9:25 AM
becomes less bitter. The glass of fresh water
(10 minutes) Adaptation to the taste of one will taste sweet. The variability in the taste
substance can affect the taste of another, of ordinary tap water following adaptation
either decreasing or increasing our sensi- to various substances will surprise many
tivity to it. Using three glasses of water (one students.
mixed with salt, one mixed with vinegar, and
one fresh), have a student volunteer come to Information from Fisher, J. (1979). Body magic. Stein & Day.
the front of the classroom. Have the student
taste the saltwater and hold it in their mouth
for a time; it will gradually taste less salty. If
the student then takes a glass of fresh water,
it will taste bitter. Have another student
volunteer come to the front of the room and

Sensation: Basic Concepts Module 1.6a 121

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