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
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 Obesity (Sight, availability, time of day) 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 -------
Gaining weight Increase in body weight Increase in # and size of fat cells Raises set point
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”
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
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