CHS AP Psychology Unit 8: Motivation, Emotion and Stress • Essential Task 8.6: Essential Task: Describe classic research findings in specific motivation systems (e.g., eating, social).
Stomach contractions (pangs) send signals to the brain making us aware of our hunger. The Biology of Hunger
Stomachs Removed Tsang (1938) removed rat stomachs, connected the esophagus to the small intestines, and the rats still felt hungry (and ate food).
The glucose level in blood is maintained by your pancreas. Insulin decreases glucose in the blood, when the level gets too low, we feel hungry. Glucose: C6H12O6 Glucose Molecule
Levels of glucose in the blood are monitored by receptors (neurons) in the stomach, liver, and intestines. They send signals to the hypothalamus in the brain. Glucose & the Brain Rat Hypothalamus
Hypothalamic Centers • The lateral hypothalamus (LH) brings on hunger (when stimulated lab animals ate!). • Destroy the LH, and the animal has no interest in eating. • The reduction of blood glucose stimulates orexin in the LH, which leads one to eat Think of LH as Large Hunger. Stimulate the LH, and you will eat! Destroy it, and you will never be hungry.
Hypothalamic Centers • The ventromedial hypothalamus (VMH) depresses hunger (satiety) • Destroy the VMH, and the animal eats excessively. Richard Howard Think of VMH as Very Minute Hunger. Stimulate the VMH and you will not want to eat. Destroy it and you will eat yourself to death.
Leptin • Fat cells in our body produce leptin • Hypothalamus monitors these levels • High levels of leptin signal the brain to reduce appetite or increase the rate at which fat is burned. • Leptin deficiency can cause obesity
The Psychology of Hunger • Environmental cues can trigger the biological responses (increased insulin production) • Memory plays an important role in hunger. Due to difficulties with retention, amnesia patients eat frequently if given food (Rodin et al., 1998). • Emotional attachment? • Social expectations • Conditioning
Body chemistry and environmental factors influence not only how much or when we feel hunger but what we feel hungry for! Taste Preference: Biology or Culture? Richard Olsenius/ Black Star Victor Englebert
Countries with hot climates use more bacteria-inhibiting spices in meat dishes. Hot Cultures like Hot Spices
Anorexia Nervosa:A condition in which a normal-weight person (usually an adolescent woman) continuously loses weight but still feels overweight. Eating Disorders Reprinted by permission of The New England Journal of Medicine, 207, (Oct 5, 1932), 613-617. Lisa O’Connor/ Zuma/ Corbis
Eating Disorders Bulimia Nervosa:A disorder characterized by episodes of overeating, usually high-calorie foods, followed by vomiting, using laxatives, fasting, or excessive exercise.
Prevalence • Eating disorders have been reported in up to 4% of adolescents and young adults. • Up to 50% of patients with AN develop bulimic symptoms, and some patients who are initially bulimic develop anorexic symptoms • The most common age of onset for AN is the midteens although in 5% of the patients, the onset of the disorder is in the early twenties. • The onset of BN is usually in adolescence but may be as late as early adulthood. • Gender Prevalence: • Both AN and BN are more commonly seen in females with estimates of male-to-female ratio ranging from 1:6 to 1:10
Cultural Considerations • Eating disorders are more frequent in industrialized societies, where there is an abundance of food and being thin, especially for females, is considered attractive. • Eating disorders are most common in the United States, Canada, Europe, Australia, New Zealand and South Africa. • The rates are increasing, especially in nonwestern countries like Japan and China, where women are exposed to cultural change and modernization.
Cultural Considerations • In the United States, eating disorders are common in young Hispanic, Native American and African-American women but the rates are still lower than in Caucasian women. • Female athletes involved in running and gymnastics, ballet dancers, male body builders and wrestlers are also at increased risk.
Reasons for Eating Disorders • Sexual Abuse:Childhood sexual abuse can be a catalyst for eating disorders later in life • Family: Younger generations develop eating disorders when raised in families in which weight is an excessive concern. • Genetics: Twin studies show that eating disorders are more likely to occur in identical twins rather than fraternal twins. • Obsessive-compulsive disorder – need to control • Depression and low-self esteem https://www.youtube.com/watch?v=GV3L0v2tNzo
Diet Industry • $20 Billion dollar a year industry (including diet books, diet drugs and weight-loss surgeries.) • 85% of customers are females • Diets have a 90% failure rate.
Obesity • The human cost of obesity https://www.youtube.com/watch?v=4Ow1uiWcn4c
Fat Cells • Fat cells are a reason why the calorie in/calorie out theory is incorrect! • We have billions of little fat cells, some almost empty, and some pretty swollen if we’re overweight. • Once a fat cell swells to capacity, it divides. This encourages nearby fat cells to divide. This increases your number of fat cells • Due to genetic predisposition, early childhood eating patterns, or adult overeating– your fat cells will never decrease. They may shrink, but their number stays the same.
Set-Point Theory • According to the set-point theory, there is a control system built into every person dictating how much fat he or she should carry – a kind of thermostat for body fat. • Some individuals have a high setting, others have a low one. • According to this theory, body fat percentage and bodyweight are matters of internal controls that are set differently in different people.
How to change the set point • Dieting does nothing • Dieting research demonstrates that the body has more than one way to defend its fat stores. • Long-term caloric deprivation, in a way that is not clear, acts as a signal for the body to turn down its metabolic rate. • The body reacts to stringent dieting as though famine has set in. • Within a day or two after semi-starvation begins, the metabolic machinery shifts to a cautious regimen designed to conserve the calories it already has on board. Because of this innate biological response, dieting becomes progressively less effective • A plateau is reached at which further weight loss seems all but impossible.
How to change the set point • The ideal approach to weight control would be a safe method that lowers or raises the set point rather than simply resisting it. • So far no one knows for sure how to change the set point, but some theories exist. • regular exercise is the most promising as a sustained increase in physical activity seems to lower the setting
Messing with Set-Point • Studies show that a person’s weight at the set point is optimal for efficient activity and a stable, optimistic mood. • When the set point is driven too low, depression and lethargy may set in as a way of slowing the person down and reducing the number of calories expended.
Sexual Motivation • Sex • a physiologically based motive to help us want to procreate and keep our species living • It is also affected by learning and values
The Physiology of Sex • Masters and Johnson (1966) describe the human sexual response cycle as consisting of four phases:
Hormones and Sexual Behavior Sex hormones effect the development of sexual characteristics and (especially in animals) activate sexual behavior.
Estrogen Female animals “in heat” express peak levels of estrogen. Female receptivity may be heightened with estrogen injections. Sex hormones may have milder affects on humans than on animals. Women are more likely to have sex when close to ovulation (increased testosterone), and men show increased testosterone levels when socializing with women.
Testosterone Levels of testosterone remain relatively constant in males, so it is difficult to manipulate and activate sexual behavior. Castration, which reduces testosterone levels, lowers sexual interest.
Sexual Problems • Men generally suffer from two kinds of sexual problems: premature ejaculation and erectile disorder. • Women may suffer from orgasmic disorders. These problems are not due to personality disorders and can be treated through behavior therapy and drugs such as Viagra.
The Psychology of Sex Hunger responds to a need. If we do not eat, we die. In that sense, sex is not a need because if we do not have sex, we do not die.
External Stimuli • It is common knowledge that men become sexually aroused when browsing through erotic material. • However, women experience similar heightened arousal under controlled conditions. • Generally speaking, though, men are aroused through pictures/visually while women are more aroused through what they read/thought-based
Our imagination in our brain can influence sexual arousal and desire. People with spinal cord injuries and no genital sensation can still feel sexual desire. Imagined Stimuli Sotographs/The Gamma-Liaison Network/ Getty Images
Adolescent Sexuality When individuals reach adolescence, their sexual behavior develops. However, there are cultural differences. Sexual promiscuity in modern Western culture is much greater than in Arab countries and other Asian countries.
Contraception (its use and lack of use) Ignorance: Many teen girls do not have the right ideas about birth control methods. Guilt Related to Sexual Activity: Guilt reduces sexual activity, but it also reduces the use of contraceptives. Minimal Communication: Many teenagers feel uncomfortable discussing contraceptives. Alcohol Use: Those who use alcohol prior to sex are less likely to use contraceptives. Mass Media: The media’s portrayal of unsafe extramarital sex decreases the use of contraceptives.
Sexually Transmitted Infections Factors that reduce sexual activity in teens. High Intelligence: Teens with higher intelligence are likely to delay sex. Religiosity: Religious teens and adults often reserve sex for a marital commitment. Father Presence: A father’s absence from home can contribute to higher teen sexual activity. Learning Programs: Teens who volunteer and tutor in programs dedicated to reducing teen pregnancy are less likely to engage in unsafe sex.
Sexual Orientation Sexual orientation refers to a person’s preference for emotional and sexual relationships with individuals of the same sex, the other sex, and/or either sex. It is self-defined. Heterosexual Bisexual Homosexual
Sexual Orientation Statistics As of 2013, Americans ages 18+ self-identified: • 1.6% of Americans with being gay or lesbian • .07% identified with bisexual • 1.1% identified with something else (asexual, I don’t believe in categories, etc) As members of a minority, homosexuals often struggle with their sexual orientation.
Homosexuality is more likely based on biological factors like differing brain centers, genetics, and parental hormone exposure rather than environmental factors. Origins of Sexual Orientation Cynthia Johnson/ Time magazine Homosexual parents
A number of animal species are devoted to same-sex partners, suggesting that homosexuality exists in the animal world. Animal Homosexuality David Hecker/ AFP/ Getty Images Wendell and Cass
Genes & Sexual Orientation A number of reasons suggest that homosexuality may be due to genetic factors. Family: Homosexuality seems to run in families. Twin studies: Homosexuality is more common in identical twins than fraternal twins. However, there are mixed results. Fruit flies: Genetic engineers can genetically manipulate females to act like males during courtship and males to act like females.