1 Mechanisms of Motivation

2 Motivation and Incentives Motivation - factors within and outside an organism that cause it to behave a certain way at a certain time Motivational state or drive - an internal condition, which can change over time, that orients an individual to a specific set of goals (e.g., hunger, thirst, sex, curiosity) Incentives - goals or reinforcers in the external environment (e.g., good grades, food, a mate)

3 Drives as Tissue Needs Homeostasis - the constancy of internal conditions that the body must actively maintain Animals do behave in accordance with their tissue needs

4 Types of Drives Regulatory drives - helps preserve homeostasis (e.g., hunger, thirst, oxygen) Nonregulatory drives - serve other purposes (e.g., sex, achievement)

5 Drives as States of the Brain Techniques for studying central drive systems include lesions and stimulation Connecting Socket Electrode Brain

6 Drives as States of the Brain The hub of many central drive systems lies in the hypothalamu s Cerebral cortex Portion of limbic system Hypothalamus Pituitary gland Brainstem

7 Hunger Drive Two areas of the hypothalamus, the lateral and ventromedial areas, play a central role in the hunger drive Hypothalamus

8 Lateral Area However, chemical lesions to specific cell bodies reduce hunger drive, but do not abolish it - most other drives appear normal Hypothalamus

9 Ventromedial Area Lesions alter digestive and metabolic processes Food is converted into fat rather than energy molecules, causing animal to eat much more than normal and gain weight Hypothalamus

10 Hunger Drive Other stimuli that act on the brain to increase or decrease hunger include satiety signals from the stomach satiety signals from the stomach leptin, a hormone indicating the amount of fat in the body leptin, a hormone indicating the amount of fat in the body Survey on eating…. Survey on eating….

11 Research on Weight Regulation and Dieting No consistent personality trait differences found between obese and non-obese people (e.g., willpower, anxiety) Dieters and obese are more likely to eat in response to stress than non-dieters Family environment of little importance in determining body weight - genetics plays a large role Number of fat-storage cells is a major determinant of body weight

12 Research on Weight Regulation and Dieting Fat cells are determined by genetics and food intake They increase with weight gain, but merely shrink with weight loss - may stimulate hunger Weight loss causes a decline in basal metabolism Fat cells Normal diet High-fat diet Return to normal diet

13 Effects of Culture and Habits on Body Weight Settling point - cluster of genetic and environmental factors that cause a person’s weight to settle within a given range Weight can be affected by factors like diet, exercise, and daily habits (e.g., stairs instead of elevator)

14 Sex Drive Increased production of testosterone and estrogen at puberty is responsible for physical differentiation Increased secretion of DHEA, primary adrenal sex hormone, is responsible for sexual feelings Final maturation of ovaries in females Final maturation of testes in males First sexual attraction in both sexes

15 Male Sex Drive Testosterone maintains sex drive in adult males castration decreases drive castration decreases drive

16 Female Sex Drive Estrous cycle controls drive in nonhuman mammals removal of ovaries abolishes drive, while hormone injections restore it removal of ovaries abolishes drive, while hormone injections restore it

17 Female Sex Drive Female monkeys and apes depend less on hormones for sexual behavior Human female sex drive may not be consistently affected by hormone cycle at all ovarian hormones play small role ovarian hormones play small role adrenal hormones like DHEA and testosterone play larger role adrenal hormones like DHEA and testosterone play larger role Homosexual attitude survey…. Homosexual attitude survey….

18 Human Sexual Orientation Orientation is an early-emerging, ingrained aspect of the self that probably does not change No consistent relationship between orientation and childhood experiences (e.g., parenting, abuse, sexual experience) Controversial findings suggest a possible relationship among prenatal stress, androgens, and the development of brain systems that play a role in sexual attraction