11

Mechanisms of Motivation

22

Motivation and IncentivesMotivation and Incentives

Motivation - factors within and outside an Motivation - factors within and outside an organism that cause it to behave a certain way organism that cause it to behave a certain way at a certain timeat a certain time

Motivational state or drive - an internal Motivational state or drive - an internal condition, which can change over time, that condition, which can change over time, that orients an individual to a specific set of goals orients an individual to a specific set of goals (e.g., hunger, thirst, sex, curiosity)(e.g., hunger, thirst, sex, curiosity)

Incentives - goals or reinforcers in the external Incentives - goals or reinforcers in the external environment (e.g., good grades, food, a mate)environment (e.g., good grades, food, a mate)

33

Drives as Tissue NeedsDrives as Tissue Needs

Homeostasis - the constancy of internal Homeostasis - the constancy of internal conditions that the body must actively conditions that the body must actively maintainmaintain

Animals do behave in accordance with Animals do behave in accordance with their tissue needs their tissue needs

44

Types of DrivesTypes of Drives

Regulatory drives - helps preserve Regulatory drives - helps preserve homeostasis (e.g., hunger, thirst, homeostasis (e.g., hunger, thirst, oxygen)oxygen)

Nonregulatory drives - serve other Nonregulatory drives - serve other purposes (e.g., sex, achievement)purposes (e.g., sex, achievement)

55

Drives as Drives as States of the BrainStates of the Brain

Techniques Techniques for studying for studying central drive central drive systems systems include include lesions and lesions and stimulationstimulation

Connecting Socket

Electrode

Brain

66

Drives as Drives as States of the BrainStates of the Brain

The hub of The hub of many central many central drive systems drive systems lies in the lies in the hypothalamushypothalamus

Cerebral cortex

Portion of

limbic system

Hypothalamus

Pituitary

gland

Brainstem

77

Hunger DriveHunger Drive

Two areas of Two areas of the the hypothalamus, hypothalamus, the lateral and the lateral and ventromedial ventromedial areas, play a areas, play a central role in central role in the hunger drivethe hunger drive

Hypothalamus

Hypothalamus

88

Lateral AreaLateral Area

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

Hypothalamus

Hypothalamus

99

Ventromedial AreaVentromedial Area

Lesions alter Lesions alter digestive and digestive and metabolic metabolic processesprocessesFood is converted into Food is converted into fat rather than energy fat rather than energy molecules, causing molecules, causing animal to eat much animal to eat much more than normal and more than normal and gain weightgain weight

Hypothalamus

Hypothalamus

1010

Hunger DriveHunger Drive

Other stimuli that act on the brain to Other stimuli that act on the brain to increase or decrease hunger includeincrease or decrease hunger include satiety signals from the stomachsatiety signals from the stomach leptin, a hormone indicating the amount of fat leptin, a hormone indicating the amount of fat

in the bodyin the body Survey on eating….Survey on eating….

1111

Research on Weight Research on Weight Regulation and DietingRegulation and Dieting

No consistent personality trait differences found No consistent personality trait differences found between obese and non-obese people (e.g., between obese and non-obese people (e.g., willpower, anxiety)willpower, anxiety)

Dieters and obese are more likely to eat in Dieters and obese are more likely to eat in response to stress than non-dietersresponse to stress than non-dieters

Family environment of little importance in Family environment of little importance in determining body weight - genetics plays a determining body weight - genetics plays a large rolelarge role

Number of fat-storage cells is a major Number of fat-storage cells is a major determinant of body weightdeterminant of body weight

1212

Research on Weight Research on Weight Regulation and DietingRegulation and Dieting

Fat cells are determined by genetics and food intakeFat cells are determined by genetics and food intake

They increase with weight gain, but merely shrink They increase with weight gain, but merely shrink with weight loss - may stimulate hunger with weight loss - may stimulate hunger

Weight loss causes a decline in basal metabolismWeight loss causes a decline in basal metabolism

Fat cells

Normal

diet

High-fat

diet

Return to

normal diet

1313

Effects of Culture and Habits Effects of Culture and Habits on Body Weighton Body Weight

Settling point - cluster of genetic and Settling point - cluster of genetic and environmental factors that cause a environmental factors that cause a person’s weight to settle within a given person’s weight to settle within a given rangerange

Weight can be affected by factors like diet, Weight can be affected by factors like diet, exercise, and daily habits (e.g., stairs exercise, and daily habits (e.g., stairs instead of elevator)instead of elevator)

1414

Sex DriveSex Drive

Increased Increased production of production of testosterone and testosterone and estrogen at estrogen at puberty is puberty is responsible for responsible for physical physical differentiationdifferentiationIncreased secretion of DHEA, Increased secretion of DHEA, primary adrenal sex hormone, is primary adrenal sex hormone, is responsible for sexual feelingsresponsible for sexual feelings

0

100

200

300

400

500

600

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age (in years)

DH

EA

leve

ls (

ng

/100

ml)

Females Males

Final maturation

of ovaries in females

Final maturation

of testes in males

First sexual

attraction in

both sexes

1515

Male Sex DriveMale Sex Drive

Testosterone Testosterone maintains sex maintains sex drive in adult drive in adult malesmales castration decreases castration decreases

drivedrive

1616

Female Sex DriveFemale Sex Drive

Estrous cycle Estrous cycle controls drive in controls drive in nonhuman nonhuman mammalsmammals

removal of ovaries removal of ovaries abolishes drive, while abolishes drive, while hormone injections hormone injections restore itrestore it

1717

Female Sex DriveFemale Sex Drive

Female monkeys and apes depend Female monkeys and apes depend less on hormones for sexual behaviorless on hormones for sexual behaviorHuman female sex drive may not be Human female sex drive may not be consistently affected by hormone consistently affected by hormone cycle at allcycle at all ovarian hormones play small roleovarian hormones play small role adrenal hormones like DHEA and adrenal hormones like DHEA and

testosterone play larger roletestosterone play larger role Homosexual attitude survey….Homosexual attitude survey….

1818

Human Sexual OrientationHuman Sexual Orientation

Orientation is an early-emerging, ingrained Orientation is an early-emerging, ingrained aspect of the self that probably does not changeaspect of the self that probably does not change

No consistent relationship between orientation No consistent relationship between orientation and childhood experiences (e.g., parenting, and childhood experiences (e.g., parenting, abuse, sexual experience)abuse, sexual experience)

Controversial findings suggest a possible Controversial findings suggest a possible relationship among prenatal stress, androgens, relationship among prenatal stress, androgens, and the development of brain systems that play and the development of brain systems that play a role in sexual attractiona role in sexual attraction