Psychology 1000 Lecture Notes - Cholecystokinin, Absenteeism, Prenatal Development

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16 Jan 2013
Chapter 10
Motivation and Emotion
The term “motivation” often triggers images of people who persevere to attain their dreams and stretch the
boundaries of human achievement. Motivation is a process that influences the direction, persistence, and vigour of
goal-directed behaviour.
Instinct Theory and Modern Evolutionary Psychology
Instinct is an inherited predisposition to behave in a specific and predictable way when exposed to a
particular stimulus.
Have a genetic basis, do not depend on learning
By conducting twin and adoption studies, behaviour geneticist seek to establish how strongly heredity
accounts for differences among people in many aspects of motivated behaviour, such as tendencies to be
outgoing or anti social
o Student reading books, playing sports, riding roller coasters
Modern evolutionary psychologists propose that many “psychological” motives have evolutionary
underpinnings expressed through the actions of genes
From this perspective, the adaptive significance of behaviour is a key to understanding motivation
o Why are we social creatures? shared resources, protection etc,
Homeostasis and Drive Theory
Homeostasis is a state of internal physiological equilibrium that the body strives to maintain
Maintaining homeostasis requires a sensory mechanism for detecting changes in the internal environment, a
response system that can restore equilibrium, and a control centre that receives information from the
sensors and activated the response system
Homeostatic regulation can also involve learned behaviours
When were hot we not only perspire, but also may seek a shady place or a cool drink
Drive Theory of motivation, physiological disruptions to homeostasis produce drives, states of internal
tension that motivate an organism to behave in ways that reduce this tension
o Hunger and thirst arise from tissue deficits
Less influential than in the past
o People behave in ways that increase rather than reduce states of arousal skipping meals in order
to diet
Incentive and Expectancy Theories
Whereas drives are viewed as internal factors that “push” organisms into action, incentives represent
environmental stimuli that “pull” an organism toward a goal
Incentive theories focus attention on external stimuli
Clark Hull argued that all reinforcement involves some kind of biological drive reduction (e.g., food is an
incentive because it reduces the drive of hunger), but this view is no longer held
Modern incentive theory emphasizes the “pull” of external stimuli and how stimuli with high incentive value
can motivate behaviour, even in the absence of biological need
o Finish a meal and be full, but eat dessert in the absence of a biological need
Incentive theories of motivation have also been powerfully applied to the study of drug abuse
Seeking and administering a drug is motivated by the positive incentive value of the drug’s effect
Incentive theories have had more in common with classical conditioning than with cognition, but expectancy
theory has broken from this tradition and given a larger role to cognition.
Expectancy X value theory, proposes that goal-directed behaviour is jointly determined by two factors: the
strength of the person’s expectation that particular behaviours will lead to a goal, and the value the
individual places on that goaloften called incentive value
These two factors are multiplied, producing the following equation: motivation = expectancy x incentive
o James works hard because she believes it will get him an A, and he values it highly
o Harrison believes working hard will get him an A, but values it lowly
Can external incentives ever decrease motivation?
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Many cognitive theorists distinguish between:
o extrinsic motivation performing an activity to obtain an external reward or to avoid punishment
o intrinsic motivation, performing an activity for its own sakebecause you find it enjoyable
According to the over justification hypothesis, giving people extrinsic rewards to perform activities that
they intrinsically enjoy may “over justify” that behaviour and reduce intrinsic motivation
If we begin to perceive that we are performing for the extrinsic rewards rather than for enjoyment, the
rewards will turn “play” into “work,” and it might be difficult to return to “play” if those rewards were to
Extrinsic rewards reduce intrinsic motivation most strongly when they are tangible and when the performer
expects rewards to be offered.
When extrinsic rewards such as praise are perceived as informative, as a means of positive feedback, they
can increase feelings of competence and intrinsic motivation.
Psychodynamic and Humanistic Theories
Freud’s (1923) psychoanalytic theory highlighted the motivational underworld
To Freud, much of our behaviour results from a never-ending battle between unconscious impulses
struggling for release and psychological defences used to keep them under control
Energy from these unconscious motives are disguised and expressed through socially acceptable behaviours
Today’s psychodynamic theories emphasize that along with conscious mental processes, unconscious
motives and tensions guide how we act and feel
o Supported by cognitive psychology and neuroscience
o Cognitive and perceptual processes outside of conscious awareness share no real common ground
Unconscious motives and tensions guide how we act and feel
Humanist Abraham Maslow believed that psychology’s other perspectives ignored a key motive: our striving
for personal growth
He distinguished between deficiency needs, which are concerned with physical and social survival, and
growth needs, which are uniquely human and motivate us to develop our potential
He proposed the concept of need hierarchy, a progression of needs containing deficiency needs at the
bottom and growth needs at the top
o Basic physiological needs, safety and security, love needs, esteem needs, cognitive needs, aesthetic
needs, self actualization
Self-actualization represents the need to fulfill our potential, and it is the ultimate human motive
“Be all that you can be”
how does the hierarchy explain why million of women live in constant hunger in order to be thin?
The Physiology of Hunger
Metabolism is the body’s rate of energy (or caloric) utilization, and about two-thirds of the energy we
normally use goes to support basal metabolism, the resting, continuous metabolic work of body cells
Several mechanisms attempt to keep the body in energy homeostasis by regulating food intake
There are “short-term” signals that start meals by producing hunger and stop food intake by producing
satiety (the state in which we no longer feel hungry as a result of eating)
Your body also monitors “long-term” signals based on how much body fat you have
These signals adjust appetite and metabolism to compensate for times when you overeat or eat too little in
the short term
Consider three points:
1. Many of us believe that hunger occurs when we begin to run low on energy and that we feel full when
immediate energy supplies are restored Hunger is not necessarily linked to immediate energy needs
2. Homeostatic mechanisms are designed to prevent you from “running low” on energy in the first place
3. Many researchers believe that there is a set pointan internal physiological standardaround which
body weight (or more accurately, our fat mass) is regulated
homeostatic mechanisms will return us to our original weight
As we gain or lose weight, homeostatic mechanisms kick in and make it harder to keep gaining or losing
weight, but do not necessarily return us to our original weight
Over time, we may “settle in” at a new weight
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Signals That Start and Terminate a Meal
o Swallowed a balloon. When it was inflated, it recorded his stomach contracts.
o The contracts did correspond to subjective feelings of hunger
Hunger “pangs” do not depend on an empty stomach.
o Animals display hunger when the nerves form their stomach and brain are cut or when people have
their stomach surgically removed.
When you eat, digestive enzymes break food down into various nutrients
Once key nutrient is glucose, a simple sugar that is the body’s (and especially the brain’s) major source of
immediately useable fuel
After a meal, some glucose is transported into cells to provide energy, but a large portion is transferred to
your liver and fat cells, where it is converted into other nutrients and stored for later use
Sensors in the hypothalamus and liver monitor blood glucose concentrations
When blood glucose levels decrease, the liver response to converting stored nutrients back into glucose
This produces a drop-rise glucose pattern
Humans and rats display a temporary drop-rise glucose pattern prior to experiencing hunger
This occurs not only when glucose levels fall and rise naturally (by about 10 percent), but also when they
are manipulated experimentally
As we eat, several bodily signals combine and ultimately cause us to end our meal
Stomach and intestinal digestion are “satiety signals
The walls of these organs stretch as food fills them up, sending nerve signals to the brain
Nutritionally rich food seems to produce satiety more quickly than an equal volume of less nutritious food,
suggesting that some satiety signals respond to food content
Chemical signals the intestines respond to food by releasing several hormonescalled peptidesthat help
terminate a meal
For example, CCK (cholecystokinin) is released into your bloodstream by the small intestine as food
arrives from the stomach
It travels to the brain and stimulates receptors in several regions that decrease eating
Signals That Regulate General Appetite and Weight
Fat cells are not passive storage sites for fat
Rather, they actively regulate food intake and weight by secreting leptin, a hormone that decreases appetite
As we gain fat, more leptin is secreted into the blood and reaches the brain, where receptor sites on certain
neurons detect it
Signals influence neural pathways to decrease appetite and increase energy expenditure
Leptin is a “background” signal
It does not make us feel “full” like CCK and other satiety signals
It regulates appetite by increasing the potency of these other signals
Thus, as we gain fat and secrete more leptin, we tend to eat less because these mealtime satiety factors make
us feel full sooner
As we lose fat and secrete less leptin, it takes more food and a greater accumulation of satiety signals to
make us feel full.
ob gene (ob = obesity) normally directs fat cells to produce leptin
Do not receive the “curb your appetite” signal mice over eat and become obese
o Daily injections made them become thinner
In a mutation of another gene (the db gene), their brain receptors are insensitive to leptin
o The “curb your appetite” signal is there, but they can’t detect it, and become obese
o Injecting mice does not reduce their food intake and weight
Genetic condition seem to be rare in humans
Are leptin injection the magic bullet? there is reason for doubt, because obese people already have ample
leptin in their blood due to their fat mass.
Brain Mechanisms
Two regions in the hypothalamus: the lateral hypothalamus (LH), seemed to be a “hunger on” centre and
the ventromedial hypothalamus (VMH), seemed to be a “hunger off” centre
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