Developmental psychology.pdf

112 The Human Organism
How do we know about such reactions? Consistently improved methods of
psychophysiological measurement have appeared in recent years, especially in the study
of intact human beings. Many of these techniques are now widely used and quite sophisticated,
and they lie behind most of the discoveries described in this chapter (Martin
& Venables, 1980).
EEG Method In the research on epilepsy, just as in Joseph Kamiya's study of brain
waves during relaxation, a record called the electroencephalogram (EEG) is often
obtained. No surgery is involved, and the subject can be prepared in a few minutes.
Pad electrodes are placed on the skull and, as brain waves are emitted and amplified,
the patterns are recorded by a writing stylus on a moving tape.
When the individual is resting, a regular EEG rhythm, called an alpha wave,
may appear. This wave occurs at a rate of about 10 cycles per second. Sometimes an
irregular rhythm occurs, indicating some type of brain disorder. Such a disorder may
be temporary, as among people who have changed time zones rapidly in transcontinental
flights and among those who have been deprived of sleep. After an appropriate
wake-sleep schedule, the deviant pattern disappears. Other irregular rhythms are permanent,
as in some psychoses and certain forms of brain damage, including epilepsy.
Normal patterns are also associated with different states of consciousness, such
as the various stages of sleep. Of particular interest in sleep is the stage in which
dreaming occurs, which reappears predictably every one and one-half to two hours.
The absence of recordable brain waves is known as a flat EEG, indicating no
measurable brain activity. It occurs in death and also in traumatic injuries, and this
finding has led to a controversial issue.
It is possible for a person's brain to be permanently injured, as shown by the
total absence of recordable waves for several minutes yet, due to the action of subcortical
centers, there can be faint heartbeats. In all medical history, no one has recovered
consciousness from this condition, but death traditionally has been interpreted
as the cessation of heartbeat. With modern life-support apparatus the heart can continue
to function yet the person can never regain consciousness. The question of life
and death now involves the quality of life and the degree of consciousness, and it has
ethical, legal, physiological, and psychological dimensions.
EKG Method For measuring changes in the rate and rhythm of the heartbeat, an
instrument known as the electrocardiograph is used. In one procedure, an electrode is
attached to each arm and each leg and another electrode is placed at various positions
on the chest. With additional apparatus, tracings are made by a stylus on a moving
sheet of paper, and this record is called an electrocardiogram (EKG). The examiner
looks for various patterns in this record, of which about a dozen have been established,
indicating different heart activity.
One significant development in the measurement of heart rate includes a portable
tape recorder attached to the small monitor. This relatively inconspicuous apparatus
can be worn on one's belt, providing a basis for measuring cardiac activity in
daily life, apart from the laboratory. Interest in this possibility for studying long-term
cardiac patterns has grown considerably in recent years (Siddle & Turpin, 1980; Figure
4.18).
GSR Method Another body response that has been of particular interest to psychologists
is the activation of the sweat glands during emotional arousal. The resulting
perspiration, especially in the palms of the hands, causes a lowering of the electrical
resistance of the skin, called the galvanic skin response (GSR). The skin becomes wet
and thus a better conductor of electricity. To measure this change, two electrodes from
a galvanometer, which records electrical potential, are connected to the palm of the
hand. The lowered resistance, or GSR, is registered by a swing of the needle of the
galvanometer.