ASSESSMENT: BRAIN ELECTRICAL ACTIVITY AND
CEREBRAL ASYMMETRY
The next time you ’re talking to some friends, you might try this quick experi-
ment. Ask your friends some reflective questions, such as “How do you feel
when you are anxious? ”or“Picture and describe the most joyous scene you
have recently been in. ”When people engage in a little reflective thought, most
tend to look off to one side. Some people consistently, although not always,
glance to the right, whereas others tend to look to the left. As described later,
the significance of this difference lies in what it may tell us about our friends ’
tendency to experience happiness or sadness. The direction in which people
look when contemplating may be a general indicator of brain activity patterns
psychologists associate with emotion.
The notion that we can examine personality with physiological measures
has been around a long time. Freud speculated that scientists would one day dis-cover the neurological underpinnings of personality. Similarly, Allport arguedthat future technological advances would identify differences in the central nerv-
ous system associated with different traits. Although we have yet to fulfill these
prophecies, personality researchers have come to use a wide variety of physio-
logical measures in their experiments. For many years now, researchers have
used physiological indicators of arousal, such as heart rate, respiration and gal-
vanic skin response. Other investigators examine hormones, immune systems,
neurotransmitters, respiration, automatic muscle reflexes, and enzymes in the
blood. More recently, researchers have turned to neuroimaging techniques to
pinpoint the location of neural activity in the brain. These techniques include
functional Magnetic Resonance Imaging ( fMRI) and positron emission tomo-
graphy (PET). In this section, we look at another example of how psychologists
use physiological measures to examine differences in brain activity level.
Measuring Brain Activity
How can we measure brain activity without going into a person ’ss k u l l ?
Fortunately, technology provides some relatively nonintrusive procedures for
obtaining these measurements. One relatively simple and inexpensive procedure
uses an instrument called an electroencephalograph (EEG) to measure electrical
activity in different parts of the human brain. Personality researchers find EEG
measurements particularly useful for several reasons. The procedure is relatively
simple and does not harm the individual in any way. Typically, small electrodesare attached to the person ’s head with hair clips and elastic straps. Participants
report that the procedure is not uncomfortable although electrode paste cansometimes leave messy spots in their hair. In addition, the EEG enables re-searchers to record brain activity in very quick intervals. Some instruments can
measure this activity within milliseconds. This sensitivity is particularly impor-
tant when looking at emotions, which often change very rapidly.
EEG data are usually described in terms of cycles per second, or waves.
One kind of wave identified through this process, known as an alpha wave ,
has proven particularly useful for research on personality and emotion. The
lower the alpha wave activity, the more activation in that region of the brain.Assessment: Brain Electrical Activity and Cerebral Asymmetry 243