How does motivation direct
and energize behavior?
Variety of approaches in
psychology
Instinct approaches
Instincts
Energy
Channels
behavior in
appropriate
direction
Instinct approach
Behavior “hard-wired” into the nervous
system
Provide survival value
More common in lower animals
Doesn’t meet the complexity of most
human behavior
Modified by experience
Drive reduction approach
Satisfying our needs
Primary drives for Biological needs
Examples: hunger and thrist
Secondary drives based on prior
experience
Examples: achievement and
belongingness
Drive reduction
Strengths:
Primary drives satisfied
Homeostasis for bio
needs
Weaknesses:
Humans and other
animals seek new
experiences
Drive reduction doesn’t
explain
Curiosity
Sensation seeking
Animals want to
increase level of
arousal
Exploration
Risk taking
Incentive approaches
Motivation’s “pull”
Behavior not
always
motivated
internally
External
motivation
Incentives
Contrasting approaches
Drive reduction
Incentive theory
“push”
“pull”
5 hours since last
meal
Ice cream truck
hunger
Palatability
(good tasting)
What are biological and social
factors that underlie hunger?
Biological and Social
Biological: based on primary drive
Social: preferences heavily influenced
by experience and culture
Ex: Grasshoppers and Worms in tacos
Ok in Mexico
Not Ok at Taco Bell in New Britain
Primary drive
Internal mechanisms regulate the
quantity of food intake
And kinds of food desired
Animals given the choice of wide variety
of foods
Choose a fairly well-balanced diet
Very rarely gain weight (except pets)
Biological factors
Chemical
composition of
blood (glucose)
Factor in
controlling eating
Monitored by
hypothalamus
On and off
switches
Motivation-Hunger
• The
hypo
cont
and
main
func
Hypothalamus as monitor
Acts like thermostat in
heating system
Heat comes on
Reaches temperature
Heat shuts off
Negative feedback
loop
Hunger switches
Damage lateral
hypothalamus (LH)
Animal refuses to
eat
LH may act as “on”
switch
Hunger sensor
Damage
ventromedial
hypothalamus
(VMH)
Animal eats too
much
VMH may act as
“off” switch
Satiation sensor
VMH rat
400% wt increase
Finicky
Prefer good tasting
food (palatable)
Not willing to work
for food
Make great house
guests
Human weight regulation
Weight set point a
key factor
Particular level of
weight the body
strives to maintain
Changing set point
Raise set point
Lower set point
Food consumption
increases
Food consumption decreases
Set point and genetics
High metabolic rate
Eat without gaining
wt
Low metabolic rate
Gain wt easily
Other factors which affect
eating
Meals by the clock
Meal size unrelated
to energy expended
Highly palatable
foods may be high
in calories
Eat for emotional or
social reasons
Theory 1: External cues and
obesity
Oversensitivity to external cues
Based on social convention
(Sight, availability, time of day)
Obesity
Insensitivity to internal cues
(stomach contractions)
Ignoring internal cues
Stanley Schacter
Early work by Stunkard
Subjects swallow gastric balloon
Balloon registers stomach contractions
Normal wt subjects reported hunger
when stomach contracted
Obese subject paid little attention to
internal cues
Govern eating by external
cues
Palatability
Subjects given either “decent” vanilla
shake or one spiked with bitter quinine
decent
bitter
Normal
10 oz
6 oz
Obese
14 oz
3 oz
Average amount of shake consumed
Availability
Have to work to get food
Bag of almonds on desk while waiting
How many subjects ate almonds
with shells without shells
Normal
10/20
11/20
Obese
1/20
19/20
Other external cues
Eat by the clock
Sight of other people eating
Social settings
Why oversentive?
Schacter: oversensitivity to external cues
causes overeating
Richard Nisbett (grad student with Schacter):
Just the reverse
Overeating causes increase in sensitivity
Overeating alters body’s set point for weight
Theory 2: Set point
Eat more to
feel satisfied
Obese Person
Higher
set point
If eat less,
become very
sensitive to
external cues
Set Point theory
Set Point -------
# of fat cells
Size of cells
Body weight
Gaining weight
Increase in body
weight
Increase in # and
size of fat cells
Raises set point
# of fat cells
Size of cells
Body weight
Losing weight
Any loss of weight
after age of two
No decrease in #
of fat cells
Decrease in size
Weight set point
doesn’t drop
Lowest possible
weight gets “stuck”
# of fat cells
Size of cells
Body weight
Restrained eaters
Fighting to loose weight
Body sending out starvation signals
Can hold themselves back (restrain)
Stay on strict diet
Give in to desire to eat
Likely to binge
Yo-Yo effect
95 % of wt lost is regained within a year
Some dieters put on more wt than lost
Famine hypothesis
Fat cells “think” there must be a famine
while dieting
Rebound when person stops diet to
help body survive the next “famine”
Theory 3: Settling point
Rapid rise in obesity in USA
10% population in 1980, 31% in 1991
Settling point: combo of genetics and
the environment we live in
Cultural differences in diet
Americans versus Asians
Fast food nation
Advice from weight loss experts
There is no easy route to wt loss
Permanent changes in your lifestyle
Set reasonable goals
Exercise: critical factor in long run
Avoid fad diets
Don’t feel guilty