心理学与生活-第31章
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babies was weakening。 Doctors quickly performed a Cesarean section。 Within minutes； 4…pound Nicole and
3…pound 14…ounce Alexis entered the world。
Immediately after birth； Nicole and Alexis joined half a dozen other babies in the Neonatal Intensive Care
Unit。 For two…and…a…half weeks； electronic devices monitored their vital signs。 Experienced nurses tended to
their physical needs and held them frequently。 Christine spent a good part of each day with her babies；
holding and rocking them and feeding them her breast milk from bottles； awaiting the day when she could
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CHAPTER3： THE BIOLOGICAL BASES OF BEHAVIOR
actually breast feed them。 Wearing diapers barely the size of cocktail napkins； the twins looked fragile and
unfinished。 With no layers of baby fat； every little rib showed。
Had Nicole and Alexis been born 20 years earlier； their first few weeks of life would have been quite
different。 Until the late 1970s； premature infants were touched as little as possible。 Parents and medical
personnel feared that any unnecessary contact with the outside world might harm the babies。 Fortunately
for Nicole and Alexis； we now know better。
Research with infant rats and humans has led scientists to conclude that brain functioning can be altered
by touch； and that； for newborns； touch is essential for normal growth and development。 Biologist Saul
Schanberg found that when rat pups were removed from their mothers； the levels of an enzyme important
for growth decreased dramatically。 The longer they were deprived of maternal contact； the less responsive
the pups became。 The effects of maternal deprivation could be reversed in only two ways： by returning them
to their mother； who immediately started to lick them； or by having a researcher vigorously stroke them with
a small paintbrush。 Shanberg concluded that； “the need for a mother’s touch is really brain based。 It is not
just nice to have it。 It’s a requirement for the normal development and growth of the baby。”
Psychologist Tiffany Field； who had collaborated with Schanberg； conducted similar stimulation studies of
premature human infants。 Her research team randomly selected 20 preemies to receive periodic massages
throughout the day； while 20 others received normal hospital treatment in the intensive care unit； treatment
that did not include massage。 According to Field； “The premature babies who were massaged for 45
minutes a day for ten days before they were discharged gained 47 percent more weight than the babies who
did not get massaged。 They were more active。 They were more alert。” Eight months later； the massaged
babies had maintained their weight advantage and were more advanced in motor； cognitive； and emotional
development。 This research is being extended and replicated in larger samples of preemies in order to
establish the power of human touch on biological and psychological health。
In the United States； more than 0。25 million infants are born prematurely each year。 Those who are touched
and cuddled leave the hospital several days sooner than usual； reducing care costs by about 3；000 per
child。 Unfortunately； not all hospitals apply what scientists have learned about the positive effects of early
touch on development。 If they did； the lives of thousands of children would be improved； saving billions of
dollars each year—both practical benefits of this basic research。
When Nicole and Alexis left the hospital； they were still small； but were developing so well that doctors felt
confident they would be all right。 At home； the babies shared a crib in the living room； where relatives and
friends who remarked on their tiny size were encouraged to pick up the babies gently and cuddle them。
Christine and her husband were acutely aware of the important role played by human touch in the optimal
development of the brain and the mental and psychical processes that it controls。
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CHAPTER 4
Sensation
LEARNING OBJECTIVES
On pletion of this chapter； students should be able to：
1。 Understand the basic processes through which sensory stimuli are converted into neural
events
2。 Describe Müller’s doctrine of specific nerve energies
3。 Relate the differences in thresholds （absolute and difference） and know why these concepts
are relevant
4。 Discuss the concepts of response bias and signal detection theory
5。 Identify the parts and functions of the human visual system
6。 Understand the basic processes involved in color vision； and the theories supporting those
processes
7。 Describe the physiological ponents of the auditory system
8。 Explain the two theories of pitch perception
9。 Define pheromones and describe their role in olfaction
CHAPTER OUTLINE
I。 Sensory Knowledge of the World
A。 Sensation is the process by which stimulation of sensory receptors produces neural
impulses that represent experiences inside or outside the body
B。 This chapter deals with sensory processes； with the sense organs and peripheral aspects of
the nervous system that put you in contact with the world around you
C。 Your senses have two basic functions
1。 Survival
2。 Sensuality
D。 While some animals specialize in one sensory medium； such as the sight of hawks； humans
are equipped with a variety of sensory mechanisms
E。 Psychophysics
1。 The study of the relationship between physical stimuli and the
behavior or mental experiences the stimuli evoke。 The oldest field in
psychology。
2。 Gustav Fechner （1801–1887）
a） The most significant figure in psychophysics
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CHAPTER 4： SENSATION
b） Coined the term “psychophysics” and developed procedures to
relate the intensity of physical stimulus to the magnitude of the
sensory experience。
3。 Absolute Thresholds and Sensory Adaptation
a） The absolute threshold for stimulation is the smallest； weakest
stimulus energy that the organism can detect
b） Operationally defined as the stimulus level at which a sensory
input is detected half of the time
c） Sensory Adaptation is the diminishing responsiveness of sensory
systems to prolonged stimulus input。 Sensory systems are more
sensitive to change in stimulus input than to steady input。
4。 Response Bias
a） The systematic tendency for an observer to favor responding in a
particular way that is unrelated to the qualities of the sensory
stimulus。 For instance； tending to say “yes” or “no” all of the time。
There are at least three sources of response bias。
i） Desire
ii） Expectation
iii） Habit
5。 Signal Detection Theory
a） A systematic approach to the problem of response bias
b） Focuses on the process of making a judgment about the presence
or absence of a stimulus
c） Unlike classical psychophysics which conceptualized a single
absolute threshold； Signal Detection Theory identifies two distinct
processes in sensory detection： Sensory Processes and Decision
Processes
i） Sensory Processes reflect an observer’s sensitivity to the
stimulus
ii） Decision Processes reflect an observer’s response bias to
the stimulus
6。 Difference Thresholds
a） The difference threshold for stimulation is the smallest physical
difference between two stimuli that can still be recognized as a
difference
b） Operationally defined as the point at which the stimuli are
recognized as different half of the time
c） The difference threshold value is known as the Just Noticeable
Difference （JND）
7。 Weber’s Law
a） The JND between stimuli is a constant fraction of the intensity of
the standard stimulus
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PSYCHOLOGY AND LIFE
F。 From Physical Events to Mental Events
1。 Sensory Physiology
a） The study of the way biological mechanisms convert physical
events into neural events
b） Transduction is the conversion of one form of energy； such as
light； into another form； such as nerve impulses
2。 The Doctrine of Specific Nerve Energies
a） Proposed by Johannes Müller in 1826
b） Different sensory experiences； such as sight and smell； do not
produce different types of nerve activity。 Rather they produce the
same type of nerve activity； but in differen
