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Motives are the needs, wants, interests, and desires that propel people
toward behavior.
Drive theories hold that motivation is based in an internal state of tension that
motivates an organism to engage in activities that should reduce this tension –
organisms seek to maintain homeostasis, or a state of equilibrium or stability.
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Incentive theories hold that motivation is regulated by external stimuli – for
example, ice cream, an A, or money. High-incentive goals, such as eating ice
cream, lead to higher drives, even if the need is low.
Most theories identify between 10 and 15 biological needs, reflecting automatic
processes for survival.
Social motives are more complicated, as they can vary depending
on experience.
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In the early 1900’s, Walter Cannon and A.L. Washburn hypothesized that there
is an association between stomach contractions and the experience of hunger;
Cannon hypothesized a causal relationship, yet people who have their
stomachs removed still experience hunger. This realization led to more
complicated theories focusing on the brain, blood sugar, and hormones.
Research in the 40’s and 50’s showed that the hypothalamus, particularly two areas called the
lateral hypothalamus (LH) and the ventromedial nucleus of the hypothalamus (VMH), are
important in hunger. The LH was thought to be the hunger center, while the VMH was thought
to be the satiety center. Subsequent research indicated that this was an oversimplified picture;
although the LH and VMH are part of the hunger circuit, they are not the key elements.
The paraventricular nucleus of the hypothalamus has recently been implicated as another
influential part of the hunger circuit.
Increased levels of ghrelin play a particularly crucial role in stimulating hunger. Ghrelin performs
double duty as a neurotransmitter in the nervous system and as a hormone in the endocrine
system. In both systems, elevated ghrelin levels are associated with increased food intake.
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Other research has focused on the role of blood glucose and digestive regulation on
hunger; when blood sugar goes down, hunger goes up. Glucostatic theory proposed
that fluctuations in blood glucose level are monitored in the brain by glucostats –
neurons sensitive to glucose in the surrounding fluid. It appears likely that hunger is
regulated, in part, through glucostatic mechanisms.
Clearly, hunger is related to biology; however, it is also regulated by
environmental factors like learned preferences. Studies show that people like
foods that are familiar to them; dog meat is a delicacy in some parts of the
world. Exposure and observational learning appear to play a part in what we
like to eat. Learning also appears to influence when and how much people eat.
Hormones circulating in the blood also appear to be related to hunger. Insulin, secreted
by the pancreas, must be present for cells to use blood glucose. Increases in insulin
increase hunger, and the mere sight and smell of food has been shown to increase
insulin.Recently, a new hormone, leptin, has been discovered to be released from fat
cells into the bloodstream. Leptin is believed to signal the hypothalamus about fat
stores in the body, causing decreases in hunger when fat stores are high.
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William Masters and Virginia Johnson conducted groundbreaking research in
the 1960s, using physiological recording devices to monitor the bodily changes
of volunteers engaging in sexual activity. They outlined four stages in the
sexual response cycle.
The excitement phase is the initial arousal, which escalates quickly. Muscle tension, respiration rate, heart rate
and blood pressure increase. Vasocongestion – engorgement of blood vessels occurs in the genitals. [Click
to continue.]
The plateau phase occurs when physiological arousal continues to build, but at a slower pace. [Click
to continue.]
The orgasm phase occurs when sexual arousal reaches its peak intensity and is discharged in a series of
muscular contractions that pulsate through the pelvic area. The subjective experience of orgasm is very similar
for men and women, although women can be multi-orgasmic. On the other hand, they are more likely to engage
in intercourse without experiencing an orgasm. [Click to continue.]
The resolution phase is characterized by subsiding physiological arousal. Men experience a refractory period
after orgasm, when they are largely unresponsive to further stimulation. This may last from a few minutes to a
few hours and increases with age.
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Evolutionary analyses of human sexual motivation have focused on the
difference between male and female parental investment. If males are to
maximize their number of fertile offspring, they might do so by mating with as
many females as possible. Females, on the other hand, must carry and then
feed their offspring, who will not survive without considerable investment on
her part. This difference in required investment has been used to explain other
gender differences in sexual activity and preferences.
Because female fertility is not itself observable, evolutionary theorists suggest that the best standin for female fertility are characteristics like youth and physical features that males have come to
regard as beautiful because they predict fertility. Males therefore should have a stronger
preference than do females for mates that are young and attractive. Conversely, females should
be more interested than are males in a mate who has resources to invest in children. Because
resources often come with age, females should generally prefer a mate older than themselves
and with characteristics predictive of future success, such as intelligence, ambition, and diligence.
Males think more about sex, and are more motivated to seek sex with many
different partners, than are females.
The resemblance between evolutionary psychologists’ predictions and common stereotypes
has led to intense criticism of these theories, and it is certainly the case that these evolutionary
considerations are not the only possible explanation of the data. More research is needed in
this area.
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Sexual orientation refers to a person’s preference for emotional and sexual
relationships with individuals of the same sex (homosexuality), the other sex
(heterosexuality), or either sex (bisexuality).
Many environmental theories explaining homosexuality have been put forth historically. Freud held that a person
must identify with the same sexed parent, or homosexuality results. Behaviorists assert that homosexuality is
learned through conditioning. Research has failed to support either theory. What has been found is that most
men and women with homosexual orientations can trace their leanings back to early childhood, suggesting a
biological basis.
Recent conceptualizations of sexuality hold that homosexuality and
heterosexuality are endpoints on a continuum.
Biological research suggests that there is a genetic predisposition to homosexuality, possibly based on the X
chromosome. Anatomical differences between gay and straight men in the size of the anterior hypothalamus
have also been found. This structure is larger in men than in women, and this study showed that gay men had
a 50% smaller AH than straight men.
Data on the prevalence of homosexuality suggests that 5-8% of the population
may have a homosexual orientation.
Some theorists believe that anatomical brain differences such as these may be due to the organizing effects of
prenatal hormones on neurological development.
The interactionist view holds that genes and prenatal hormones shape a child’s temperament, which initiates a
chain of events that ultimately shapes sexual orientation.
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Achievement motivation is generally measured using the Thematic Apperception Test,
a projective test which requires a subject to write or tell stories about what is happening
in pictures of people in ambiguous scenes. Achievement motivation involves the need
to excel, especially in competition with others.
The cognitive component of emotion involves subjective feelings that have an
evaluative aspect. The cognitive appraisal of an event is an important element
in emotional experience. Emotional processes are also tied to physiology, but
in extremely complex ways.
People who are relatively high in the need for achievement work harder and more
persistently, they tend to delay gratification well and to pursue competitive careers.
Situational factors have been shown to influence achievement motivation, causing it to
increase when the probability of success and the incentive value of success are high.
Additionally, the pursuit of achievement can be influenced by a fear of failure, so that
the motive to avoid failure stimulates achievement.
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The physiological arousal associated with emotion occurs through the actions
of the autonomic nervous system. The autonomic nervous system is
responsible for the highly emotional fight-or-flight response. The galvanic skin
response (GSR) measures autonomic activation – the device that measures
autonomic fluctuations while a person is questioned is called a polygraph or lie
detector (really an emotion detector). Polygraph tests measure emotion, which
may or may not be due to deceit; they are inaccurate often enough that they
are deemed not reliable enough to be submitted as evidence in most types
of courtrooms.
In the brain, the limbic system is the emotional circuit (the hypothalamus, the
amygdala, and adjacent structures); Joseph LeDoux (1996) has shown that
the amygdala plays a particularly central role in modulating emotions.Sensory
inputs that trigger fear arrive first in the thalamus and then take a fast path
directly to the amygdale, as well as a slow path through the cortex.
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Behaviorally, emotions are expressed through body language and facial
expressions. Research indicates considerable cross-cultural similarities in
the ability to differentiate facial expressions of emotion. The facial-feedback
hypothesis holds that facial muscles send signals to the brain that help it
recognize the emotion being experienced, as when we smile and feel better.
Cross-cultural similarities have also been found in the cognitive and behavioral
components, although display rules, or norms for regulating appropriate
expression of emotion, vary from culture to culture. In this video, researchers
explore different emotional expressions across cultures by interviewing and
surveying people from different cultures.
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The James-Lange theory of emotion holds that you see a snake, your pulse
races, and you feel afraid because your pulse is racing.
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The Cannon-Bard theory holds that you see a snake, the information is sent
to the thalamus, which relays the signals simultaneously to the cortex and to
the autonomic nervous system.
Schacter’s Two-Factor theory holds that you feel autonomic arousal and
search your environment to see why: if there’s a snake, for example, you
feel fear.
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