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motionless flies. But let one zoom by and the frog’s “bug detector” cells snap awake. (As
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
TEACH
Teaching Tip
Students may get bottom-up and top-
down processing confused. Help them
remember the difference between the
two concepts by picturing a pyramid,
with data points (pieces of information)
at the bottom and one consolidating
theory at the top. Then the terms may
make more sense:
• Bottom-up processing—we Copyright © Bedford, Freeman & Worth Publishers.
process this way when we have
no prior knowledge. We start at
the bottom with individual pieces
of data and work our way up to a
theory or conclusion.
• Top-down processing—we
process this way when we have
prior knowledge. We start at the
top with the theory and work down
as we process specific details
based on our expectations and
experiences.
03_myersAPpsychology4e_28116_ch01_002_163.indd
116 Unit 1 Biological Bases of Behavior
03_HammerTE4e_47547_ch01_2a_163_4pp.indd
Kermit the Frog said, “Time’s fun when you’re having flies.”)
• Male silkworm moths’ odor receptors can detect one-billionth of an ounce of chemical
sex attractant per second, released by a female one mile away (Sagan, 1977). That is why
there continue to be silkworms.
CULTURAL In Module 1.6, we’ll look at what psychologists have learned about how we sense our
AWARENESS world; in Module 2.1, we’ll explore how we perceive our world. Let’s begin by considering
Pay close attention to the difference some basic principles of both sensation and perception.
between sensation and perception.
Many people mistakenly believe that
the brain perceives situations in an Basic Concepts of Sensation and Perception
objective, calculating way. In fact,
the brain implements a number of How do we create meaning from the blizzard of sensory stimuli that bombards our body
biases and filters that influence our 24 hours a day? In its silent, cushioned, inner world, our brain floats in utter darkness. By
experience in the world, and those
applied are often influenced by our itself, it sees nothing. It hears nothing. It feels nothing. So, how does the world out there get
culture. in? To phrase the question scientifically: How do we construct our representations of the
external world? How do a campfire’s flicker, crackle, heat, and smoky scent activate neural
connections? And how, from this living neurochemistry, do we create our conscious experi-
ence of the fire’s motion and temperature, its aroma and beauty?
sensation the process by
which our sensory receptors Processing Sensations and Perceptions
and nervous system receive and Indiana Adams’ curious mix of perfect vision and face blindness illustrates the distinction
represent stimulus energies from
our environment. between sensation and perception. When she looks at a friend, her sensation is normal: Her
sensory receptors detect the same information any sighted person’s would, and her nervous
sensory receptors sensory
nerve endings that respond to system transmits that information to her brain. Her perception — the processes by which her
stimuli. brain organizes and interprets sensory input — is almost normal (see Module 2.1). Thus, she may
perception the process by recognize people from their hair,
which our brain organizes and gait, voice, or particular physique,
interprets sensory information, just not from their face. Her expe-
enabling us to recognize objects rience is much like the struggle
and events as meaningful.
bottom-up processing any human would have trying to
recognize a specific penguin.
information processing that Under normal circumstan-
begins with the sensory
receptors and works up to the ces, sensation and perception
brain’s integration of sensory blend into one continuous
information. process. In this module and
top-down processing Module 2.1, we slow down that
information processing process to study its parts; in
guided by higher-level mental real life, your sensory and per-
processes, as when we construct
ceptual processes work toge-
perceptions drawing on our
ther to help you decipher the
experience and expectations. world around you. As your
brain absorbs the information
in Figure 1.6-1, bottom-up
processing enables your sen-
sory systems to detect the lines,
Figure 1.6-1 angles, and colors that form the
What’s going on here?
Our sensory and perceptual images. Using top-down pro-
cessing, you interpret what your
processes work together to help
us sort out complex images, senses detect. We miss our
including the hidden donkey rider own typos because we know
in Sandro Del-Prete’s drawing, © Sandro Del-Prete what we intended, which (top-
Homage to Leonardo de Vinci. down) controls what we read.
116 Unit 1 Biological Bases of Behavior
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116 07/02/24 5:26 PM