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Module 1.6a

Module 1.6a Sensation: Basic Concepts

LEARNING TARGETS

1.6-1 Explain the three steps that are basic to all of our sensory systems.
1.6-2 Explain the difference between absolute thresholds and difference
thresholds.

1.6-3 Explain the function of sensory adaptation.
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.

hen Indiana Adams awoke on New Year’s Day in 2020, she decided to buy her
Copyright © Bedford, Freeman & Worth Publishers.
husband exercise equipment. As she scrolled through the social media market-
Wplace, a used psychology textbook cover caught her attention. Adams’ vision is
perfect, but her perception is not. A former model and actor, Adams noted that the woman
on the textbook cover wore clothes that evoked memories of one of her photoshoots. But
Adams has prosopagnosia — face blindness — which means she can’t even recognize her
own face.
She went into her bedroom and showed her husband the picture. “That’s you!” he said.
And we [DM and ND] were that textbook’s authors.
People with face blindness sometimes struggle socially.
On one occasion, Adams was shopping and complimented
another woman on her cute clothes. When the woman
didn’t respond, Adams realized she was actually looking
at herself in the mirror — and talking to her own reflec-
tion! Other people with face blindness report being aloof
or experiencing distress when they confuse coworkers and
strangers with loved ones. Face-blind people sometimes
pretend to recognize people, just in case they turn out to
be someone they know. One woman found a way to use
her face blindness to build friendships (Dingfelder, 2019).
“When I was walking to class, if someone seemed to look
my way, I smiled. If they smiled, I stopped to chat,” she said.
“Before long, the whole campus was brimming with close,
personal friends of mine.”
Unlike Adams, most of us have a functioning area on
the underside of our brain’s right hemisphere that helps
us recognize a familiar human face, including our own,
as soon as we detect it — in only one-seventh of a second
(Jacques & Rossion, 2006). Our remarkable ability illus-
trates a broader principle: Nature’s sensory gifts enable each
animal to obtain essential information. Other examples:
• Human ears are most sensitive to sound frequencies
that include human voices, especially a baby’s cry. Red Chopsticks/Getty Images
• Frogs, which feed on flying insects, have cells in their
eyes that fire only in response to small, dark, mov-
ing objects. A frog could starve to death knee-deep in Could that be me?

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