Motivation

1. Motivation

2. Motivation 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?

3. Kinds 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 • we’ll come back to these in Ch. 15

4. Just right Just right Too little Too much Too little Too much Deviation produces a drive e.g., too little food  hunger Drive gives motivation to restore homeostasis e.g., hunger  eating  satiation Homeostatis • homo (equal) + stasis (state) • body’s 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

5. Hypothalamus • “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

6. Hunger • example of a regulatory drive mediated by homeostatis • clear biological basis with environmental influences

7. Lateral Hypothalamus • “hunger” centre • neural recording • food • conditioned stimulus associated with food • stimulation  eating • lesions  starvation

8. Ventromedial Hypothalamus • “satiation” centre • stimulation  rats don’t eat • lesions  rats become obese

9. Increase in blood glucose above set point Eat Inhibit LH Excite VMH Accumulation of body fat above set point Satiety Decrease in blood glucose below set point Excite LH Inhibit VMH Stop Eating Decrease in body fat below set point Hunger

10. Study this on your own Peter Gray FQ 6-10 esp. Fig. 6.4 Tuesday’s “Test Yourself” question will be based on the various factors that control hunger

11. 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 Twin Studies

12. Logic 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 doesn’t • When we observe a trait exhibiting high concordance for MZ but not DZ twins, we can conclude the trait is strongly affected by genetics

13. Comparison of Concordance Rates Between MZ & DZ Twins

14. Adoption 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)

15. Change in weight (twin B) Change in weight (twin A) Genetic 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

16. Why 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

17. Dieting • gaining/losing weight can be very difficult • WWII studies • male prisoners ate 7,000 calories per day for 6 mos. • most gained < 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 > 10 lbs.

18. Dieting affects your set point Set Point Set Point Set Point • 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 • cutting down on carbs (esp. simple carbs = sugar) may help • Atkins diet • low carbs, high protein & fat • seems to work but controversial • nutritionists recommend low fat Too little Too much Too little Too much Too little Too much 150 lbs 150 lbs 150 lbs 130 lbs 170 lbs 130 lbs 170 lbs 130 lbs 170 lbs Before dieting During dieting After dieting

19. Eating Disorders Anorexia Nervosa • signs • refusal to maintain normal body weight (< 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

20. Cultural 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

21. 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?

24. Special K ad “Ironically, she’s the one worried about her weight.” Keep your expectations reasonable and stay healthy!

25. Sex and Drugs (Sorry, no Rock & Roll)

26. Sex 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

27. Sex 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

28. What do women want? Men who like children Older men Men with good financial prospects Men with good social status

29. What 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

30. What 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. I’m tall, handsome and athletic.

31. How would evolutionary biologists explain this pattern?

32. Pleasure 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., > 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?

33. Dopamine and Reward • many of the pleasure centres contain dopaminergic neurons • dopamine is released during many rewarding activities (e.g., eating when you’re 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