How does motivation direct and energize behavior?

Variety of approaches in psychology

Instinct approaches

Instincts EnergyChannels 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

“push”

5 hours since last meal

hunger

Incentive theory

“pull”

Ice cream truck

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

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 muchVMH may act as “off” switchSatiation 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 Food consumption increases

Lower set point 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

Obesity

Oversensitivity to external cues

Based on social convention

(Sight, availability, time of day)

Insensitivity to internal cues

(stomach contractions)

Ignoring internal cues

Stanley Schacter Early work by Stunkard Subjects swallow gastric balloonBalloon registers stomach contractionsNormal wt subjects reported hunger when stomach contractedObese 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

Obese Person Higher set point

Eat more to feel satisfied

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