Page 117 - 2024-bfw-MyersAP4e

Module 1.6a

Transduction

1.6-1 Which thr ee steps ar e basic to all of our sensory systems?
1.6-1 Which three steps are basic to all of our sensory systems?

Our sensory systems perform the amazing feat of transduction : They convert outside

energy into a form our brain can use. Vision processes light energy. Hearing processes sound
waves. All of our senses
• receive sensory stimulation, often using specialized receptor cells,
• transform that stimulation into neural impulses, and
• deliver the neural information to our brain.
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
Transduction is rather like translation — in this case, of a physical energy such as light

waves into the brain’s electrochemical language. Psychophysics studies the relation-
ships between the physical energy we can detect and its effects on our psychological
Copyright © Bedford, Freeman & Worth Publishers.
experiences. transduction conversion of one
Later in this module, we’ll focus on specific sensory systems. How do we see? Hear? form of energy into another. In
Feel pain? Taste? Smell? Keep our balance? In each case, a sensory system receives, trans- sensation, the transforming of
physical energy, such as sights,
forms, and delivers the information to our brain. And our senses work together. sounds, and smells, into neural
Let’s first explore some strengths and weaknesses in our ability to detect and interpret impulses the brain can interpret.
stimuli in the vast sea of energy around us. psychophysics the study
of relationships between the
Thresholds physical characteristics of stimuli,
such as their intensity, and our
psychological experience of them.
1.6-2 How do absolute thresholds and difference thresholds dif fer?
absolute thresholds
1.6-2 How do absolute thresholds and difference thresholds differ?
How do
How do
absolute threshold the
minimum stimulus energy
At this moment, each of us is being struck by X-rays and radio waves, ultraviolet and infra- needed to detect a particular
red light, and sound waves of very high and very low frequencies. To all of these we are blind stimulus 50 percent of the time.
and deaf. In contrast, other animals with differing needs detect a world that lies beyond our signal detection theory a
experience. Migrating birds stay on course aided by an internal magnetic compass. Bats and theory predicting how and
dolphins locate their prey using sonar, bouncing echoing sound off objects. Bees navigate when we detect the presence
on cloudy days by detecting invisible (to us) polarized light. of a faint stimulus ( signal )
Our senses open the shades just a crack, allowing us a restricted awareness of this vast amid background stimulation
( noise ); assumes there is no
sea of energy. But for our needs, this is enough. single absolute threshold and
that detection depends partly
Absolute Thresholds on a person’s experience,
expectations, motivation, and
To some kinds of stimuli we are exquisitely sensitive. Standing atop a mountain on an alertness.
utterly dark, clear night, most of us could see a candle flame atop another mountain 30 miles
(nearly 50 kilometers) away. We could feel the wing of a bee falling on our cheek. We could
smell a single drop of perfume in a three-room apartment ( Galanter, 1962 ).

German scientist and philosopher Gustav Fechner (1801–1887) studied the edge of SPOTLIGHT ON:

.
our awareness of these faint stimuli, which he called an absolute threshold To test your Gustav Fechner
absolute threshold for sounds, a hearing specialist would send tones, at varying levels, into

each of your ears and record whether you could hear each tone ( Figure 1.6-2 ). The test
results would show the point where, for any sound frequency, half the time you could detect
®
the sound and half the time you could not. That 50-50 point would define your absolute AP Science Practice
threshold. Research
Detecting a weak stimulus, or signal (such as a hearing-test tone), depends not only on
its strength but also on our psychological state — our experience, expectations, motivation, Depending on their research
question, signal detection theorists
and alertness. Signal detection theory predicts when we will detect weak signals (mea- might use non-experimental or

sured as our ratio of “hits” to “false alarms”). Signal detection theorists seek to understand experimental methods. Could
why people respond differently to the same stimuli, and why the same person’s reactions you identify the difference? These
methods are described in Unit 0 .
vary as circumstances change.
Sensation: Basic Concepts Module 1.6a 117

03_myersAPpsychology4e_28116_ch01_002_163.indd 117 15/12/23 9:24 AM