Title: Motivation
1Motivation
2Motivation
- Why do people do the things they do?
- reflexes
- simple, unlearned responses to specific stimuli
- -often mediated by direct connections in spinal
cord - learned (conditioned) behaviors
- physiological needs ? drives ? increase
likelihood of behavior - cognition
- thoughts, beliefs and strategies about
consciously directed behaviors that best satisfy
drives
- What are the basic drives?
- Why are some things more motivating
(reinforcing) than others?
3Kinds of Drives
- regulatory
- primary biological maintenance
- survival
- regulated by homeostasis
- breathing, hunger, thirst, pain, sleep
- non-regulatory
- long-term maintenance
- sex, attachment, nurture, novelty, aggression
- long-term comfort
- self-esteem, power, achievement,
self-actualization - well come back to these in Ch. 15
4Homeostatis
- homo (equal) stasis (state)
- bodys maintenance of a constant state
- e.g., body temperature, blood glucose, salts in
bodily fluids, sympathetic vs. parasympathetic NS - analogy thermostat
- set point optimal level
Just right
Too little
Too much
Stable internal state
5Hypothalamus
- hub for drive systems
- closely linked to the hippocampus (memory),
amygdala (emotion), pituitary gland (releases
hormones) and cerebral cortex (cognition)
If I had to give up just a cubic millimeter of
tissue from some part of my brain, the last place
I would want it taken from is the hypothalamus.
-- Peter Gray
6Hunger
- example of a regulatory drive mediated by
homeostatis - clear biological basis with environmental
influences
7Lateral Hypothalamus
- hunger centre
- neural recording
- food
- conditioned stimulus associated with food
- stimulation ? eating
- lesions ? starvation
8Ventromedial Hypothalamus
- satiation centre
- stimulation ? rats dont eat
- lesions ? rats become obese
9Hunger
10Study this on your own
Peter Gray FQ 6-10 esp. Fig. 6.4
Tuesdays Test Yourself question will be based
on the various factors that control hunger
11Twin Studies
- Optional refresher Gray p. 58
- Identical Twins
- monozygotic (MZ) originate from one zygote
- 1 zygote 1 sperm 1 egg
- 100 relatedness
- Fraternal Twins
- dizygotic (DZ) originate from two separate
zygotes - 50 relatedness
- same as any two siblings
12Logic of Twin Studies
- Both identical and fraternal twins share the same
environment (same age, same parents) - Only MZ twins share exactly the same genes
- Concordance both twins share the same trait
- Discordance one twin has a trait that the other
doesnt - When we observe a trait exhibiting high
concordance for MZ but not DZ twins, we can
conclude the trait is strongly affected by
genetics
13Comparison of Concordance Rates Between MZ DZ
Twins
TRAIT MZ () DZ ()
Blood type 100 66
Eye color 99 28
Mental retardation 97 37
Measles 95 87
Idiopathic epilepsy 72 15
Schizophrenia 69 10
Diabetes 65 18
Identical allergy 59 5
Tuberculosis 57 23
14Adoption Studies
- Examine whether adopted children bear a greater
resemblance to their biological parents and
siblings or their adoptive parents and siblings - Can suggest whether genes or environment play a
greater role (nature vs. nurture)
15Genetic Factors in Obesity
- Adoption Study
- (Sorensen et al., 1992)
- weight of adopted children is more correlated
with biological parents than adoptive parents - Twin Study
- (Bouchard et al., 1990)
- 12 pairs of identical male twins were given an
extra 1000 calories per day above the amount
required to maintain their initial weight - The weight that an individual gained was very
similar to the weight gained by his twin...and
showed the same distribution on the body
16Why Obesity?
- Obesity may reflect a thrifty gene -- one that
promotes efficient metabolism when feasts are few
and famines frequent - Although this gene may have been beneficial in
other environments, it may be maladaptive in
modern society where food is ample and encouraged
17Everybodys Dieting!
http//www.nationaleatingdisorders.org
600 lbs ? 220 lbs in 2 years
18but who is losing weight?
- Popular diets
- few people lose big time
- e.g., 10 of dieters lost gt10 of weight
(Dansinger, 2005, JAMA) - Weight Watchers is one of the better diets
- Average result 3.2 of weight loss maintained
for 2 years (Tsai Wadden, 2005, Ann Intern Med) - extreme diets such as the Atkins diet have more
dropouts (50) than moderate diets such as Weight
Watchers (35) (Dansinger, 2005, JAMA)
- People who lost gt10 of weight for gt 1 yearWing
Hill cited in Globe Mail, Dec. 31, 2005) - 1 hour of brisk activity daily
- didnt eat out
- ate breakfast
- got feedback (i.e., regularly weighed themselves)
- were consistent through the week and year (didnt
binge on weekends Christmas) - worked on stress management
19Gaining Losing Weight
- gaining/losing weight can be very difficult
- WWII studies
- male prisoners ate 7,000 calories per day for 6
mos. - most gained lt 40 lbs (expected 170 lbs)
- eventually stopped gaining weight
- upon cessation, most returned to initial rate
(except those with family history of obesity) - semistarvation in non-military volunteers
- most men lost 25 of body weight
- frequent psychological problems
- some men had problems losing gt 10 lbs.
20Dieting affects your set point
Set Point
Too little
Too much
150 lbs
130 lbs
170 lbs
Before dieting
- yo-yo dieting makes you gain weight
- long-term lifestyle changes and gradual weight
loss much better than short-term diet blitzes - eat less, exercise more
- being fit is more important than being thin
21Eating Disorders
- Anorexia Nervosa
- signs
- refusal to maintain normal body weight (lt 85 of
expected weight) - intense fear of gaining weight
- disturbed body image
- amenorrhea (missed at least 3 menstrual periods)
- usually begins in adolescence in upper-class
Caucasian girls - 15-20 eventually die from the disorder
- Bulimia Nervosa
- signs
- binge eating
- inappropriate behavior to prevent weight gain
(vomiting, laxatives, fasting, excessive
exercise) - typically affects average and slightly overweight
women - also primarily upper-class Caucasian women but
more common in men and minorities than anorexia - seldom fatal but causes health problems
Christy Henrich, Olympic gymnast, 11 months
before her death in 1993. 22 years old, 4 10,
60 pounds
22- Which body for your sex would be your ideal?
- Which body would the opposite sex find most
attractive? - Which body is most typical the modern average in
our society?
23(No Transcript)
24(No Transcript)
25Cultural Ideals
- ideal female form has changed over time
fertility goddess 30,000 years ago
Rubens 1639
Kate Moss 1994
- cultures tend to value what is rare and difficult
to achieve - in some developing countries in Africa, obesity
is considered a sign of being upper class - in most developed countries where food is ample,
obesity is undesirable
26The Ideal Female Over the Years
27Special K ad Ironically, shes the one worried
about her weight.
Keep your expectations reasonable and stay
healthy!
28Sex and Drugs (Sorry, no Rock Roll)
29Sex Drive Hormones
- androgens
- main class of male hormones
- testosterone
- differences in testosterone levels during
development can determine sex differences - primary sex characteristics (genitalia)
- secondary sex characteristics (e.g., body hair)
- brain development
- different for gay men?
- related to sex drive in both sexes (but not as
strongly in females) - high testosterone correlated with higher rates of
sexual activity - estrogens
- main class of female hormones
- lead to breast development, widened hips and
rounded body contours - estrogen levels do not correlate well with sexual
interest
30Sex Drive Other Factors
- Cultural influences
- education, religion, culture, peer attitudes
- more influential for women
- Situations
- more influential for women
- Genetics
- affects sexual orientation
- twin/adoption studies suggest genetic component
to homosexuality - evidence for genetic markers for homosexuality in
men but not women
31What do women want?
Men who like children
Older men
Men with good financial prospects
Men with good social status
32What do men want?
Physical attractiveness
Sex, sex, sex
- (Clark Hatfield, 1989)
- Attractive men and women hired to approach
strangers of the opposite sex on a college campus - "I have been noticing you around campus. I find
you very attractive." - "Would you go out with me tonight?"
- "Would you come over to my apartment tonight?"
- "Would you go to bed with me tonight?"
In some cultures, chastity
33What do people look for in partners?
- Single female, aged 25, seeks well-educated,
established male, aged 22-28, interested in
long-term relationship and children. Must be
kind, generous and dependable.
- Single male, aged 30, who likes having fun seeks
slim attractive female, 18-25. Im tall,
handsome and athletic.
34How would evolutionary biologists explain this
pattern?
35Pleasure Centre
- rats (Olds Milner, 1950s)
- place an electrode in various brain structures
- bar pressing causes electrode stimulation
- at most locations ? no effect
- at a few locations (associated with hypothalamus
or limbic system), rats would continuously press
bar to receive self-stimulation - e.g., gt 7,000X/hour for many hours
- rats would choose self-stimulation over food and
water even though they would become exhausted and
die of starvation - humans
- stimulation of certain sites (associated with
limbic system) can be pleasurable in a sexual
sort of way or a happy drunk way - Could this type of reward be an all-purpose
motivation/reward centre?
36Dopamine and Reward
- many of the pleasure centres contain dopaminergic
neurons - dopamine is released during many rewarding
activities (e.g., eating when youre hungry) - dopamine agonists increase self-stimulation of
pleasure centres - dopamine antagonists decrease self-stimulation of
pleasure centres - many highly-addictive drugs (heroin, nicotine,
cocaine) enhance dopamine
37Video Clip Pleasure Centre
Cavanagh Psych1 Disk3 (453) Emotion Pleasure
- What would it be like to be a human with an
electrode in your pleasure centre? - How much self-stimulation does it take before a
rat becomes satiated? - To what lengths will rats go to achieve
self-stimulation? How could you measure this? - What do addictive drugs have in common?