PSYB64 Chapter 14 Emotion,Aggression, and Stress
an emotion has two major components: a physical sensation, such as a rapid
heartbeat, and a conscious, subjective experience or feeling, such as feeling scared.
Emotions typically demonstrate valence: A positive (attractive) or negative (aversive)
reaction to an object or event
So emotions possess a positive or negative quality.
The Evolution of Emotion
Charles Darwin concluded that emotional expression must have evolved. Evolution
implies beneficial change, so how have emotions improved our ancestors chances of
(1)One possible advantage of emotions is their contribution to general arousal.
When the brain perceives a situation requiring action, emotions provide the arousal
needed to trigger a response
As indicated by the Yerkes-Dodson law, arousal interacts with the complexity of a
task to predict performance.
For simple tasks, such as outrunning a predator, greater arousal tends to lead to
superior performance. For more complex tasks, however, we see deficits in
performance when arousal levels are too high ex: performing poorly on an
exam because we're too stressed or anxious
(2) Emotions also manage our approach and withdrawal behaviors relative to particular
The positive emotions associated with eating contribute to our seeking food when
we are hungry, and the negative emotions elicited by observing a large snake or
rotting food lead to avoidance, providing obvious advantages for survival
(3) Emotions also enhance survival by helping us communicate.
Nonverbal communication, consisting of facial expression and body language,
provides an important source of social information
Ex: body expressions of fear communicate important information in an
immediate, arousing, and contagious manner
Expression and Recognition of Emotion
Human adults are typically good at expressing and interpreting emotions accurately
Controlling Facial Expression:
Although we use our whole bodies to express emotion, humans pay the most attention
to the face, in particular to the eyes
Movement of the human face is controlled by two cranial nerves, the facial nerve
(cranial nerve VII) and the trigeminal nerve (cranial nerve V).
The facial nerve controls the superficial muscles attached to the skin which are
primarily responsible for facial expressions
The trigeminal nerve controls the deeper facial muscles attached to the bones of
the head that are responsible for chewing food and speaking
The facial nerve has five major branches, with each branch serving a different portion
of the face.
The facial nerves originate in the two facial nuclei located on either side of the
midline in the pons
These nuclei do not communicate directly with each other. This organization makes
it possible for emotional expression to vary in intensity from one half of the face to the other
The facial nuclei receive input from the primary motor cortex located in the
precentral gyrus of the frontal lobe as well as from several subcortical motor areas.
The upper third of the face is controlled differently than the lower two thirds
The upper third of the face receives input from both the ipsilateral and contralateral
facial nerves, whereas the lower two thirds of the face are controlled primarily by
the contralateral facial nerve.
When a person suffers damage to the motor cortex of one hemisphere, there is
relatively little impact on the muscle tone of the upper face, which continues to
receive ipsilateral input from the healthy hemisphere.
However, the contralateral lower face will be paralyzed and will appear to sag.
Two major pathways control facial expression: One involves input from the motor
cortex and is primarily responsible for voluntary expression. The second is a subcortical
system that is primarily responsible for spontaneous expression
People with damage to the primary motor cortex are unable to smile on command
on the side of the mouth contralateral to their damage. However, when they hear a
good joke, they can show some spontaneous smiling on the otherwise paralyzed
side of the face.
This condition is known as volitional (voluntary) facial paresis (paralysis)
because the ability to express voluntary emotion is impaired.
In contrast, people with Parkinsons disease, which involves subcortical motor
structures including the substantia nigra and basal ganglia, lose the ability to smile
spontaneously while retaining the ability to smile on command.
This condition is referred to as emotional facial paresis because the ability to
express spontaneous emotions is impaired
Biological Influences on Emotional Expression:
Some major emotional expressions appear to be universal across human cultures:
anger, sadness, happiness, fear, disgust, surprise, contempt, and embarrassment
Most people, regardless of culture, have little difficulty identifying these major
Also supporting the notion that emotional expression has a strong biological basis is
that Childrens capacities for emotional expression and recognition develop according
to a fairly regular timeline, with relatively little influence by experience.
Infants who are blind from birth show a progression in the development of social
smiling that is similar to that of sighted infants, in spite of being unable to learn by
Monozygotic (identical) twins are more similar than dizygotic (fraternal) twins in the
age at which they begin to show fear of strangers
Consistent timelines for the development of emotional expression and recognition also
characterize nonhuman primate development.
Rhesus monkeys raised in isolation still showed fear of pictures of other monkeys
engaged in threatening behaviors. The development of their fear response was
about the same as that of monkeys raised in normal social circumstances
Environmental Influences on Emotion:
Although our basic emotional responses seem largely innate, the influences of culture
and learning modify emotional expression.
Ex: medical doctors undergo training to withhold emotions, such as disgust, that
would be inappropriate to express to patients.
People make more intense facial expressions in response to odors when in a group as
opposed to when they are alone
Japanese students watching an emotional film alone were more expressive than when they watched with unfamiliar peers.
In contrast, the emotional expression of American students did not vary
significantly depending on whether they viewed the film alone or in a group
Blind babies exhibit social smiles at about the same age as sighted infants (around the
age of three months), but by adulthood, differences in emotional expression have
Congenitally blind adults show the same numbers and types of facial expressions as
sighted adults. However, observers have more difficulty interpreting their
expressions, with the interesting exception of happiness, perhaps the ultimate
Individual Differences in Emotion:
Individuals are quite different from one another in their overall levels of emotional
Infants who are highly reactive to environmental stimuli are at greater risk for
anxiety and mood disorders later in life. Extremely low-reactive infants have a
greater tendency toward antisocial behavior.
A study of psychopaths incarcerated for murder indicated that these men
responded much less than control participants to slides of pleasant, neutral, and
One source of these individual differences appears to be the amygdala, which plays a
crucial role in the interpretation of emotional stimuli
Individuals with major depressive disorder show higher levels of activity in the
amygdala than participants without any mood disorder
When participants are shown photographs designed to elicit negative or neutral
moods, those with higher amygdala activity in response to viewing negative photos
also reported more negative mood
Can We Spot a Liar?:
People who are deliberately lying slip in predictable ways: The normally articulate
person stumbles verbally, adding ums and uhs as he or she struggles to assemble
a plausible lie.
Tend to stiffen the head and upper body. In contrast to the stiffer upper body, the feet
They nod their heads less frequently and do not use hand gestures as much as when
theyre telling the truth
Inappropriate smiling and laughing can result from the nervousness caused by lying.
In the United States, lack of eye contact is interpreted as a sign of dishonesty, but in
many other cultures, eye contact is viewed as an impolite expression of dominance.
Polygraph, or lie-detector, tests are widely used by both law enforcement and
employers, in spite of their unreliability
a panel of experts evaluated polygraph data and dec