Lecture: Motivation & Emotion
Lecture script · about 15–20 minutes spoken · Week 10
Opening
A coach watches a runner bounce on her toes at the start line. A hospital nurse notices that a person recovering from surgery has stopped finishing meals. A bakery leaves its door open so the smell of fresh bread drifts onto the sidewalk. Each of them is working with the same two forces: what moves people to act, and what people feel while they do it.
That's this lecture. In Week 3, you met the hypothalamus and the amygdala, two small structures deep in the brain. In Week 6, you saw how rewards make a behavior more likely. Week 9 was about how you think. Now we turn to what pushes and pulls you, and what a feeling is made of. Next week, in Week 11, the course follows how all of this grows and changes across a lifetime.
Here's the plan. First, four ways to explain motivation and one model that ranks human needs. Then hunger, as a case study. Then we'll take an emotion apart and run one scary moment through three theories. If you keep one sentence, keep this one: needs push and incentives pull, but a feeling is not one thing.
1. Name the force: motivation and instinct theory
Think about the last time you did something hard on purpose. Maybe you stayed up to finish a project, or got up early to train. Something got you moving, and something kept you pointed at the goal until you were done.
That force has a name. Motivation is a need or desire that energizes behavior and directs it toward a goal. Notice the two halves. Energizes means it starts you and keeps you going. Directs means it aims you somewhere: to the kitchen, not to the couch.
The earliest scientific answer to "where does motivation come from?" was instincts. Picture a young bird building its very first nest. It never watched another bird do it, and yet it builds the nest the way every member of its species does. Instinct theory is an early view that explained behavior with instincts, complex unlearned behavior patterns that are fixed across a species; naming a behavior an instinct describes it without explaining it.
That last part is the problem. Early writers called almost everything an instinct, from curiosity to shyness. And a label that fits everything explains nothing. If I tell you that people help because of a helping instinct, I haven't told you anything you didn't already know. And most human behavior is learned, as you saw in Week 6.
Pause and try this. Someone says, "She studies so much because she has a studying instinct." Does that explain her behavior?
Think about what the label actually predicts.
Here's the answer. No; it only renames the behavior, while a real explanation names something you could measure, like a need, a reward, or a level of arousal.
2. Follow a drive: need, drive, and homeostasis
It's past midnight. You skipped dinner to finish a lab report, and now you're standing at the open fridge. Your stomach is growling, and you can't think about anything else. You eat some leftovers, and a few minutes later the restless feeling is gone.
That night runs a loop, and drive-reduction theory names it. It's the theory that a biological need creates a drive, an aroused state of tension, that pushes behavior toward meeting the need and restoring homeostasis. Three terms are packed in there. A need is a lack of something the body requires, such as food or water. A drive is an aroused, uncomfortable state of tension, such as hunger or thirst, that a need produces and that pushes a person to act until the need is met. And homeostasis is the body's tendency to keep a steady internal balance and to return to it after a change.
So the midnight snack goes like this. Need: your body is short on food. Drive: you feel hunger as tension. Behavior: you eat. Homeostasis: the need is met and the tension fades. Need, drive, behavior, homeostasis, always in that order.
But here's the limit. Drive reduction explains motives that start inside the body and stop once a need is met. Plenty of your motives don't work that way.
Pause and try this. In the midnight snack, which part is the drive: the empty stomach, the hunger, or the eating?
Take a second and pick one.
Here's the answer. The hunger; the lack of food is the need, the hunger is the tension that need creates, and the eating is the behavior.
3. Find the sweet spot: arousal theory and the Yerkes–Dodson law
A runner signs up for a marathon. For hours, the race will raise her heart rate, her fatigue, and her nerves. No bodily need is being met. She's choosing more tension, not less. Drive reduction can't explain that.
Arousal theory can. It's the theory that people are motivated to keep their level of physical and mental arousal comfortable, so they sometimes seek excitement and raise tension on purpose rather than only reducing it. Arousal is how stirred up you are, from drowsy at one end to panicked at the other. When life is dull, people look for stimulation. When it's too intense, they look for calm.
Arousal also changes how well you perform. The Yerkes–Dodson law is the finding, from Yerkes and Dodson in 1908, that performance is best at a moderate level of arousal, with the best level lower for a difficult task than for an easy one.
Picture a hill. On the left, a runner at the start line is bored and sluggish, and she starts slowly. On the right, a runner's nerves have tipped into panic, legs shaking, and she starts poorly too. At the top of the hill, a runner who feels alert and ready, with some nerves but not too many, gets the best start.
Now shift the task. A hard exam full of new problems is a difficult task, and for that, the top of the hill sits at a lower level of arousal. One honesty note: psychologists treat this law as a broad pattern for people on average, not an exact formula for you.
Pause and try this. Two tasks: a familiar warm-up jog and a hard exam. For which one is the best level of arousal lower?
Picture the hill for each before you answer.
Here's the answer. The hard exam; the law says the best level of arousal is lower for a difficult task than for an easy one.
4. Feel the pull: incentive theory and its limit
A student is offered a scholarship for keeping top grades. Over the next few weeks, he studies longer and starts papers earlier. Nothing inside his body is out of balance. Something outside him is pulling.
That's incentive theory: the theory that external rewards, such as money, grades, or praise, pull behavior toward them, in contrast to internal needs that push it. You already know the machinery from Week 6. A reward that follows a behavior is reinforcement, and it makes the behavior more likely. Incentive theory looks at that same reward from the front, as a goal that draws you forward before you act.
Now a harder case. Someone spends weekends building furniture in a garage workshop. Nobody pays for the chairs, nobody judges them, and there's no prize. They keep at it for years, for the satisfaction of the craft. Look for the outside reward. There isn't one. So incentive theory can't explain this hobby. The motive comes from the activity itself, and the next idea gives that kind of motive a name.
Pause and try this. Where does the force start in drive reduction, and where does it start in incentive theory?
Say both answers to yourself first.
Here's the answer. A drive starts inside the body as a need and pushes, while an incentive starts outside the person as a reward and pulls.
5. Stack the needs: Maslow's hierarchy and its limits
Imagine a week when the rent is late, the phone is about to be cut off, and a big project is due. It's hard to think about who you want to become when you're worried about a place to sleep. Abraham Maslow, one of the founders of the humanistic movement from Week 1, built a model around that experience.
Maslow's hierarchy of needs is Abraham Maslow's 1943 model that ranks five levels of need, from physiological up to self-actualization; it is a descriptive model whose strict ordering is not well supported by evidence. From the bottom up, the five levels are physiological needs like food and sleep, then safety, then belongingness and love, then esteem. At the top sits self-actualization, the drive to develop your talents and become the most complete version of yourself. Maslow proposed that lower needs tend to demand attention first.
Back to the furniture maker. The hobby doesn't feed or house anyone, so it isn't physiological or safety. No one sees or praises the chairs, so belonging and esteem don't explain it well. The person is developing a talent for its own sake. In Maslow's terms, that's self-actualization.
But research has not found that people climb the levels in a strict order. Artists have made great work while poor and hungry. People in hard times often put love, faith, or community first. And the ranking differs across cultures; in many communities, belonging comes before personal achievement.
Pause and try this. True or false: Maslow's hierarchy is a proven law that every person climbs one level at a time.
Decide, and name your reason.
Here's the answer. False; it's a widely used descriptive model, and the evidence doesn't support its strict bottom-to-top ordering.
6. Trace hunger: the hypothalamus, ghrelin, and leptin
You finish a big holiday meal and push back from the table, full. Then someone brings out dessert, and suddenly you find room. Your stomach didn't empty in the last minute. Something besides an empty stomach is shaping what you eat.
Start with the body. The hypothalamus helps regulate hunger by responding to signals that travel in the blood. Two of those signals are hormones. Ghrelin is a hormone released mainly by the stomach that signals hunger to the brain, rising when the stomach has been empty for a while. Leptin is a hormone released by fat cells that signals fullness to the brain and helps regulate appetite over the long run.
To keep them apart, remember: ghrelin growls, leptin lets go. On the skipped-dinner night, your stomach stayed empty for hours, ghrelin rose, and the hypothalamus responded, so you felt the drive to eat. Over the longer run, leptin tells the brain how much energy is stored. One caveat about the wording: these hormones help regulate appetite, and neither one alone causes a person to eat or to stop.
Now the mind. Learned, social, and cultural influences shape what, when, and how much people eat. You may feel hungry at noon because you always eat at noon. You may crave popcorn the moment you walk into a movie theater. People eat differently at a shared table than alone. What counts as breakfast differs from one family to the next. That's why the dessert tray works on a full stomach.
Pause and try this. Which hormone signals hunger, and which one signals fullness?
Use the phrase to check yourself.
Here's the answer. Ghrelin signals hunger and comes mainly from the stomach, while leptin signals fullness and comes from fat cells.
7. Take a feeling apart: the three components of emotion
Think about the last time you were truly embarrassed. Maybe you waved back at someone who was waving to the person behind you. Your face got hot. You looked down and gave an awkward laugh. And a voice in your head said, "Everyone saw that."
That's three things at once. An emotion is a response of the whole person that combines physiological arousal, expressive behavior, and a conscious cognitive appraisal of what a situation means. Physiological arousal is the body's stirred-up state, like a pounding heart or sweaty palms. Expressive behavior is the outward signs others can see or hear, like a facial expression or a tone of voice. Cognitive appraisal is your conscious reading of what the situation means for you.
Now the bear. You're hiking at dusk, you round a bend, and a bear steps onto the path. Your heart pounds and your mouth goes dry; that's arousal, your sympathetic nervous system from Week 3 getting you ready to act. Your eyes go wide and you freeze, then back away slowly; that's expressive behavior. And you think, "That's a bear, and I could get hurt"; that's the appraisal.
For fear in particular, the amygdala plays a central role. It's involved in the fear response and in strengthening memories that carry emotional weight, which is why you might remember that bend in the trail for years. But no single structure is the whole of an emotion. Week 14 returns to the body's stress response in depth.
Pause and try this. On the trail, which component is the thought "I could get hurt"?
Name the component before you go on.
Here's the answer. Cognitive appraisal; it's your conscious reading of what the moment means for you.
8. Run the bear three times: James–Lange, Cannon–Bard, and two-factor
Here's the question that's divided psychologists for over a century. When the bear appears, which comes first: the pounding heart or the feeling of fear? Three theories give three answers. The fair way to compare them is to give each one the same bear.
First, the James–Lange theory: the theory of emotion that the body reacts to an event first and the feeling is the experience of that bodily reaction. It's named for William James, whom you met in Week 1, and for a second researcher, Lange. So: you see the bear, your heart pounds, you tremble, and then you notice your body, and that noticing is the fear. You feel afraid because you tremble.
Second, the Cannon–Bard theory: the theory that an event triggers the bodily reaction and the conscious feeling at the same time, so neither one causes the other. You see the bear, and your brain sends two signals at once. One sets your heart pounding. The other produces the feeling of fear. They arrive together.
Third, the two-factor theory: Schachter and Singer's 1962 theory that physiological arousal plus a cognitive label for that arousal together produce the emotion. You see the bear and your heart pounds. You look for a reason, notice the bear, and label the arousal "fear." Arousal plus a label is the emotion. And the same pounding heart at the top of a roller-coaster drop might get the label "thrill."
So the theories disagree about order and about labels. James–Lange says body first. Cannon–Bard says together. Two-factor says arousal first, then a label that decides which emotion it is.
Pause and try this. A description says, "Your heart races, you notice the bear, and you decide the feeling is fear." Is that Cannon–Bard or two-factor?
Look for the label in the description.
Here's the answer. Two-factor; the arousal comes first and a cognitive label decides the emotion, while Cannon–Bard needs no label at all.
Closing
Let me pull it together in the order we built it. Motivation energizes and directs behavior, and calling a behavior an instinct only names it. Drive reduction runs need, drive, behavior, homeostasis. Arousal theory explains why people seek excitement, and the Yerkes–Dodson law puts the best performance at a moderate level, lower for hard tasks. Incentives pull from outside, and a hobby nobody pays for shows their limit. Maslow's five levels run from physiological to self-actualization, as a description, not a law. The hypothalamus helps regulate hunger, ghrelin signals hunger, and leptin signals fullness, while habits and culture pull too. An emotion is arousal, expression, and appraisal, and the amygdala is central to fear. And the bear showed the three theories side by side.
Next in this module come the slide deck, the Readings & Resources page, the lecture tutorial, the practice set, and the quiz, then the discussion, the assignment, and the Analysis Workshop. Next week, in Week 11, Development Across the Lifespan, the course follows how a mind and its feelings grow from infancy to old age.
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