NS12: Motivation

Health Behaviour and Society CourseJunior Cycle 2006/07

Semester 1: Basic Psychological Concepts

Dr. Anthony Montgomery

Dr. Anthony Montgomery

Dr. Anne Hickey

MOTIVATION

Definition: A need or desire that serves to energise behaviour and to direct it towards a goalMotivation is inferred from observable behaviour (similar to intelligence, personality)Involves an interplay between NATURE (the physiological ‘push’) and NURTURE (the cognitive & cultural ‘pulls’)

Human Motivation

Distinction between Biological Motives, e.g., hunger, sex; & Social Motives, e.g., affiliation, need for achievementAbraham Maslow (1970): Combines physiological & psychological drives into HIERARCHY OF NEEDS

The Motivation of Hunger and Eating

What causes us to feel hungry?1) Cannon & Washburn (1912): “Spit and Rumble” Theory:

Hunger = walls of empty stomach contracting & rubbing against each otherThirst = decreased salivary flow due to loss of body fluid

But: Both animals & humans with gastrectomy continue to experience hunger;Higher intake of low calorie food than high-calorie foodTheories now focus on: i) The role of the Brain

ii) The role of Blood Sugariii) The role of Hormones

Hunger Motivation: 1. The role of the brain

The function of the HYPOTHALAMAUS:a) Lateral Hypothalamus (LH): “start

centre” - i.e., creates hunger, stimulates eating

b) Ventromedial Hypothalamus (VMH): “stop centre” - i.e., depresses hunger, stops eating

Hunger - the Hypothalamus

LH: stimulation Well-fed animal begins to eat

destruction starving animal not interested in food

VMH: stimulation animal stops eating

destruction animal eats more often & becomes grossly overweight

Hunger - the HypothalamusBUT now clear that LH & VMH are part of a bigger NEURAL CIRCUIT with PARAVENTRICULAR NUCLEUS (PVN) of hypothalamus playing important modulating roleContemporary theories focus NOT on anatomical centres but on neural circuits that regulate eating by monitoring input from range of physiological processes

Glucostatic hypothesis: Hunger occurs when level of blood glucose becomes low

detected by glucose-sensitive neurons (glucostats)

in turn, activate neural circuits in brain (liver glucostatshypothalamus via vagus nerve)

(Vagus nerve also indicates stretching of stomach walls;

Other neurons indicate calorific value of stomach contents)

Hunger Motivation: 2. The role of blood sugar (body chemistry)

Hunger Motivation: 3. The role of hormones

Main hormones identified:1. Insulin:secreted by pancreas;

: extracts glucose from blood (depleted/absent in diabetes); : Stimulates hunger

2. Leptin (discovered 1995): produced by fat cells, released into bloodstream; : higher levels of fathigher levels of leptin; : leptin levels hunger

Hunger - A Physiological Drive

Messages re. stomach, liver, circulating hormones & body chemistry integrated in HYPOTHALAMUS

Psychology of Hunger

1. Learned preferences & habits:

• what to eat is learned• e.g. culturally - Eskimo

delicacy - fresh clotted seal blood; habits acquired in early life.

Psychology of Hunger

2. Food-related cues: ‘externals’ - eating triggered by presence of food‘internals’ - eating triggered by internal physiological state.

3. Stress: increased arousal stimulates eating?

4. Social: e.g. 3 meals/day hunger at time for meal, BUT do not eat hunger subsides and again just before scheduled time for next meal.

Hunger, Eating, Weight and Health

Hunger, Eating & Weight: Obesity

Body Mass Index:Obese = BMI of 30+ Mortality risk & risk of

diabetes, heart disease, gall stones

25-30% people in US; approx. 20% Irish males; less than 20% Irish females

Self-esteem, stereotyping, discrimination

Obesity and Bahrain

32% of women and 25% of men were obese (BMI ≥30.0 kg/m2)Although 28% of participants (564) had body mass index ≥30 kg/m2, only 42% (267) of these obese individuals rated themselves as overweight.

Source: Ann Saudi Med 2001;21(3-4):183-187.

Obesity: Causes1. Physiological:i) Genetics: body weight (BMI) of adopted children

correlates with biological parents; genetic heritability = 61% in men, 73% in women

ii) Fat cells: size & number - ?divide - low metabolic rate

iii) Set Point: “weight thermostat”: predisposes us to keep our body within particular weight range

Body weight - hunger, energy expenditure, metabolic rateBody weight - hunger, energy expenditure, metabolic rate

Obesity: Causes: Set Pointiii) Set point maintained by Leptin, which monitors

fat stores - under-secretion in obesity?Set points and metabolism ‘set point’ higher than average?;weight loss hunger, metabolism

Obesity: Causes

2. Psychological:i) Learned behaviourii) ? Lack of impulse control?iii) ? Inability to delay gratification?iv) Unhappiness, depression?

ii) - iv) largely unsupported empirically

[Useful website: http://www.healthpromotion.ie/topics/obesity/]

Hunger, Eating & Weight: Body Dissatisfaction

Body shape associated with attractiveness, control & success

High levels of weight concern in womenMost girls and women would like to be thinnerMost men would like to be same or larger

Body DissatisfactionConceptualised as either:

Discrepancy between perception of body size and real body size; ORDiscrepancy between real body size and ideal body size; ORUnhappy with aspects of body shape

Hunger, Eating & Weight: Eating Disorders

Psychological influence on eating behaviour

homeostatic pressures overwhelmed by motive for thinnessAnorexia Nervosa: significant weight loss (15%+ below normal) BUT feels fat, fears obesity; 90%-95% females; late adolescence +; 0.5 - 1.5% prevalence Bulimia Nervosa: private, ‘binge-purge’ episodes; predominantly women; late teens - early 20’s; 2.0 - 3.0% prevalence

Eating Disorders: Influences

Models: 1950’s - ‘60’s - weighed 8% less than average women; 1990’s - weigh 23% less thinner than 95% of women

Eating Disorders: Influences

Woman with “Barbie” figure would have a BMI of 16.6Department store mannequins - women with similar body fat would not menstruate

Eating Disorders: Influences

While women aspire to ideal of thinness, males aim for denser, athletic, “muscled” look;HOWEVER, relative to women, the prevalence of eating disorders in men is 20:1

Eating Disorders in Men

Irish Times Health Supplement, Tuesday 12th October 2004.

Causes of body dissatisfaction

MediaSocial class?Family?Ethnicity?Beliefs - e.g., about beauty; role of women; material success; achievement

ALL assume high level of control (I can never fulfil all of these demands)

• Only controllable factor may be way we look

Body dissatisfaction = expression of lack of control?

[Useful website: http://www.bodywhys.ie/]

Human Motivation: the Achievement Motive

Definition: The need to master difficult challenges, to out-perform others and to meet high standards of excellence

Correlates positively with career success and upward social mobility

people with high need for achievement tend to select tasks of intermediate difficulty, where there is a moderate degree of challenge and reasonable probability of success, and where there is a reasonable pay-off (incentive value) for success

Willingness to engage in achievement behaviour influenced by motivation to avoid failureMotive to avoid failure can stimulate achievement BUT can also result in person avoiding trying

Motivation and Emotion

Emotion can cause Motivation - e.g., joy felt after winning tennis tournament may motivate you to practice tennis more;Motivation can cause Emotion - e.g., motivation to win a tennis game may cause great anxiety during the match (may impede performance) & great joy if the match is won, or gloom if it is not.

BUT, Motivation & Emotion not the same thing

Reading

Weiten Chapter 10, pages 293-298; 306-308; 451-453. PsychtrekUnit 8 Modules a) & b).

Barkeling Brittaet al. Vision and eating behaviour in obese subjects. Obesity Research 2003; 11: 130-134