Theories of MotivationHunger MotivationEating Disorders Intro Psych Module 26 Nov 2-6, 2009 Classes #28-30
Motivation • The underlying processes that initiate, direct and sustain behavior in order to satisfy physiological and psychological needs or wants
Theories of Motivation • Instinct Theory • Drive Reduction Theory • Arousal Theory • Optimal Level Hypothesis • Incentive Theory
Instinct Theory • Instinct • Complex unlearned response triggered by a stimulus or complex stimulus • Do humans have instincts? • Early Darwinian Theory (1800’s) proposed the idea of instinct, arising from genetic endowment • William James (1890) proposed an instinct theory in humans • Instincts were goal directed predispositions to behavior
Instinct Theory • Paradox in Psychology: • As others were showing that animal behavior could be modified by learning (Thorndike), James was proposing that much of human behavior was unlearned • William McDougall (1908) followed… • Suggested their were 18 instincts
Instinct Theory • McDougall (1908) theorized that motivated behaviors are instinctual: • Unlearned • Uniform in expression (do not change with practice) • Universal (all members of a species show the same behavior)
Too many limitations… • By 1924 instinct theory was becoming obsolete as there were several criticisms: • Too many instincts • Researchers came up with 5759 of them • Logic was circular • i.e. the only evidence that an instinct exists was the behavior it supposedly explained • He’s an “overachiever” because he’s “hard-working” • She’s “hard-working” because she’s an “overachiever” • Just meaningless labels with no explanations
Drive Reduction Theory(Hull, 1943) • Supporters of this theory believe that when a need requires satisfaction, it produces drives • These are tensions that energize behavior in order to satisfy a need • Thirst and hunger are, for instance, drives for satisfying the needs of eating and drinking, respectively
Drive Reduction Theory • Drives have been generally established as primary and secondary… • Primary drives satisfy biological needs and must be fulfilled in order to survive • Homeostasis is the motivational phenomenon for primary drives that preserves our internal equilibrium. This is true, for example, for hunger or thirst • Secondary drives satisfy needs that are not crucial to a person's life
Criticism • Critics felt that this theory was inadequate in explaining secondary drives
Arousal Theories • Optimal Level Hypothesis
Optimum Arousal Theory:Hebb (1955) and Zuckerman (1984) • This theory argues that we all have optimal levels of stimulation that we try to maintain… • Optimal Level Hypothesis • we seek an optimal level of arousal • too little stimulation, we seek an increase • too much, we seek to decrease
Eysenck (1967) • Extraversion-Introversion • Introverts were over-aroused individuals therefore they try to keep stimulation to a minimum • Extroverts were under-aroused individuals, therefore they tried to increase stimulation
Eysenck (1967) • Cortical Arousal Differences • Eysenck suggests that the difference between introverts and extroverts depends on the ascending reticular activating system (ARAS) • Causes introverts to be “stimulus shy” • Causes extroverts to be “stimulus hungry”
Cortical Arousal Differences • Geen (1984) • Introverts and extraverts choose different levels of stimulation, but equivalent in arousal under chosen stimulation • Extroverts chose to hear louder noises than introverts • After put in their chosen environment their HR’s are the same • This seems to suggest that being at their preferred level of stimulation results in the same overall level of arousal for both groups
Geen (1984) • Researcher tested four other groups: • Introverts placed in environment that other introverts had chosen (II) • Introverts placed in environment that extroverts had chosen (IE) • Extroverts placed in environment that other extroverts had chosen (EE) • Extroverts placed in environment that introverts had chosen (EI)
Geen (1984) • II = similar HR as free choice introverts • IE = higher HR than free choice introverts when forced to listen to extroverts’ noise • EE = similar HR as free choice extroverts • EI = lower HR than free choice extraverts when forced to listen to introverts’ noise
Geen (1984) • Performance on a learning task was also affected: • Introverts did best in introvert-selected environment • Extraverts did better in extravert-selected environment • Practical implications: • Roommates? • Mate Selection?
Does it explain the psychopathic behaviors??? • Serial killer
Criticism of Optimum Arousal Theories • People differ greatly in the optimal level of arousal they seek… • These theories do not explain why
Incentive Theory • Viewpoint on motivation that is different than instinct, drive , and arousal theories • Suggests that behavior is pulled rather than pushed… • Emphasizes the role of environmental stimuli that can motivate behavior by pulling people toward them rather than pushing people to satisfy a need (as in the drive-reduction theory) • Suggesting that people act to obtain positive incentives and avoid negative incentives • Explains secondary drives much better than drive-reduction theory
Criticism • Some behaviors seem to be pushed as well
Abraham Maslow (1908-1970) • Born in Brooklyn, NY • His parents were uneducated Jewish immigrants from Russia • Hoping for the best for their children – they pushed them hard towards education • He became very lonely as a youth and found his refuge in books • To satisfy his parents, he entered law school at CCNY and then Cornell
Abraham Maslow • Against his parents wishes, he married his first cousin and moved with her to Wisconsin where he became interested in psychology and gets his BA in 1930, MA in 1931, and Ph.D. in 1934 at the Univ. of Wisconsin • In 1935, he returns to NY and works with Thorndike at Columbia and eventually begins teaching full-time at Brooklyn College and then becomes chair of psych department at Brandeis where he begins his crusade for humanistic psychology
Maslow’s Hierarchy of Needs (1970) • Abraham Maslow proposed that there are five levels of motives, or needs, arranged in a hierarchy: • Physiological • Safety • Belongingness and love • Esteem • Self-actualization • We must satisfy needs or motives low on the hierarchy before we are motivated to satisfy needs at the next level
Physiological Needs • Physiological needs are basic, instinctual needs for air, food, water, and sex, among others. These needs must be at least partially met in order to ascend the hierarchy. • These needs can also be arranged in their own hierarchy.
Safety Needs • Safety needs include things such as shelter, security, and protection from physical and emotional harm.
Belonging Needs • These needs are met by having meaningful relationships, such as significant others, friends and children
Esteem Needs • This level has two sub-levels • Low esteem needs are the needs for the respect of others – need for recognition, etc. • Higher esteem needs are the needs for self respect –to achieve, to be competent, to be independent, etc.
Self Actualization • Self actualization involves becoming the mostcomplete person that you can be – your full potential
Criticisms • Some critics felt that it is possible to skip levels • Others felt that they could not be applied universally
Theories of Hunger Motivation What triggers our motivation to eat? • Internal Factors • An empty stomach? • Body Chemistry • Hypothalamus • Set Point Theory • External Factors • Externality Hypothesis • Other Factors • Emotion • Habit • Attention
Internal Factors • An empty stomach? • Early researchers thought that hunger pangs were important - caused by contraction of stomach • Cannon and Washburn (1912) tested the hypothesis that the contraction of the stomach is the cue to start eating • Tested this by having Washburn swallow a balloon and measuring contractions of the stomach by looking at contractions of the balloon (changes in air pressure go out stomach via tube to measuring device)
An empty stomach? • Tsang (1938) • Removed rats stomachs and attached their esophagus to their small intestine • They still displayed actions associated with hunger
Body Chemistry • Blood Glucose • This is a simple sugar used by most cells in the body for energy - most food ultimately gets converted to blood glucose • Decreasing blood glucose levels sense of hunger • Insulin • This is a hormone that increases the flow of glucose into body cells, diminishing the amount of glucose in the blood by converting it into stored fat • Decreasing blood glucose levels sense of hunger
Body Chemistry • Glucagon • This hormone helps convert stored energy supplies (stored fat) back into blood glucose • Increasing blood glucose levels hunger decreases
Lesions of Hypothalamus • The destruction or stimulation of the lateral and ventromedial areas causes animals to ravenously decrease or increase their weight • See picture on page 375 for example of increase
Set Point Theory • Set point is the weight that your body wants to be… • It is a self-regulatory system that maintains your body weight • If you starve yourself the hypothalamus activates compensatory mechanisms, your metabolism slows so that energy stores are used more sparingly and the amount of insulin that is produced increases so that more of the food that you take in remains as fat (this makes it possible to maintain weight on a meager diet)
What triggers our motivation to eat? • External Incentives • Rodin (1981) • Like Pavlov’s dogs people learn to salivate in anticipation of appealing foods • Externality Hypothesis (Schacter, 1978) • Did research on obese humans • They argue that the difference between obese and normal weight subjects is that the obese are overly responsive to external stimuli (cues for eating)
Externality Hypothesis • VMH-lesioned rats and obese humans are similar in interesting ways: • Both are more "finicky" than controls. Both are less willing to work for food • VMH-lesioned rats don't eat as much of a bad tasting food as do control rats • Obese humans don't drink as much of a bad-tasting milk shake as do control humans • VMH-lesioned rats don't bar-press for food on "lean" schedules as readily as do the control rats • Obese humans eat fewer peanuts than do control humans if they have to shell them, but more if they don't have to do this work
Externality Hypothesis • These findings support Schacter's conclusion that both VMH-lesioned rats and obese humans are more sensitive to external cues related to food than to the internal cues provided by their bodies. • Obese humans are more likely to eat more when they are misled into thinking it's lunchtime than are control humans - again evidence of the influence of external cues • Social Factor is another external cue • Eating around others often increases food intake
Other Factors • Emotion • Depressed people may eat too much or too little • Habit • Meal time - ancient Romans only ate two meals a day. We eat three - if we miss a meal, we feel hungry at that meal time • Attention • Awareness vs. non-awareness
Eating Disorders • Obesity • Anorexia Nervosa • Bulimia Nervosa
Obesity • Weight which is 20-40% above the normal standard for a person’s height (BMI over 30 kg/m2) • Rates of obesity are climbing and have risen from 12 to 20 percent of the population since 1991. • An ominous statistic which indicates that the epidemic of obesity may get even worse is that the percentage of children and adolescents who are obese has doubled in the last 20 years • Why is this happening?
Basal Metabolic Rate • Basal metabolic rate (BMR) is the amount of energy expended while at rest in a neutrally temperate environment, in the post-absorptive state (meaning that the digestive system is inactive, which requires about twelve hours of fasting in humans). • If you've noticed that every year, it becomes harder to eat whatever you want and stay slim, you've also learnt that your BMR decreases as you age. Likewise, depriving yourself of food in hopes of losing weight also decreases your BMR, a foil to your intentions. • M > W (more muscle) • Exercise increases BMR
Obesity • Weight which is 20-40% above the normal standard for a person’s height • Rates of obesity are climbing and have risen from 12 to 20 percent of the population since 1991. • Why is this happening?
Obesity • Why do some people become seriously overweight? • Emotional problems • Depression • Anxiety • Sedentary lifestyle • Too much TV and not enough exercise • Genetics • Higher set point
What factors help prevent obesity? • Preventing obesity must begin in childhood • Breastfed children less obesity • Encouraging children to exercise and eat healthy foods • don’t use “special food” as a reward – Stanek et al. (1990) • children tend to be more interested in a “forbidden food” –– Mennella et al. (2001) • Limiting television watching • Problem with adult modeling, increase consumption of snacks low in nutrients and watching TV during meals increase consumption of salty snacks and pop and less fruit and vegetables – Goldberg et al. (2001) • Many ads have low-nutrient beverages and sweets – Story and Faulkner (1990)
How is obesity treated? • Fad Diets • Exaggerated claims based on false theories • Potentially harmful • Weight Cycling • Set point theory? • Psychological ramification