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PSYCH 447 (25)


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University of Waterloo
Richard Ennis

Chapter 13- Motivation & Emotion • Motivation - a general term for a group of phenomena that affect the nature, strength, or persistence of an individual’s behaviour o a driving force that moves us to a particular action • includes two types of phenomena, o stimuli that have become associated with pleasant or unpleasant events motivate approach or avoidance behaviours • many approaches to motivation: physiological, behavioural, cognitive, and social • three important categories of motivated behaviours: eating, sexual behaviour, and aggression o important to the survival of the individual & of the species • situations that motivate our behaviour also provoke emotions What is Motivation? • We are motivated to perform a behaviour to gain a reinforcer or to avoid a punisher Biological Needs: • Regulatory Behaviours - a behaviour that tends to bring physiological conditions back to normal, thus restoring the condition of homeostasis (eg. Eating, drinking, hunting, shivering, etc) o Complex organisms possess physiological mechanisms that detect deficits or imbalances and restore the organism to its full potential • Homeostasis - process by which important physiological characteristics (such as body temperature and blood pressure) are regulated so that they remain at their optimum level • Deficits or imbalances motivate us because they cause us to perform appropriate regulatory behaviours • Regulatory system has FOUR essential features: system variable, set point, detector, and correctional mechanism o System Variable - variable controlled by a regulatory mechanism; for example, temperature in a heating system o Set Point - optimum value of the system variable in a regulatory mechanism; set point for human body temperature, recorded orally, is approximately 37 degrees Celsius o Detector - in regulatory process, a mechanisms that signals when the system variable deviates from its set point o Correctional Mechanism - a regulatory process, the mechanisms that is capable of restoring the system variable to the set point • Negative Feedback - process whereby the effect produced by an action serves to diminish or terminate that action; Regulatory systems are characterized by negative feedback loops o is an essential characteristic of all regulatory systems • Drive Reduction Hypothesis - hypothesis that a drive (resulting from physiological need or deprivation) produces an unpleasant state that causes an organism to engage in motivated behaviours; reduction of drive is assumed to be reinforcing • Drive - a condition, often caused by physiological changes or homeostatic disequilibrium, that energizes an organism’s behaviour o Act of eating reduces hunger, and this drive reduction is reinforcing • An individual can survive without sexual behaviour; but sex drive is certainly motivating, and sexual contact is certainly reinforcing • Many events that we experience as reinforcing are also exciting or drive increasing • Experiences that we really want to repeat are those that increase, rather than decrease our level of arousal Physiology of Reinforcement: • Electrical stimulation of parts of the brain can reinforce an animal’s behaviour • Electrical stimulation of the brain is reinforcing because it activates the same system that is activated by natural reinforcers & by drugs that people commonly abuse o Function is to strengthen the connections between neurons that detect discriminative stimulus and the neurons that produce operant response Optimum-Level Theory: • Removal or avoidance of an aversive stimulus produces negative reinforcement • Optimum-Level Hypothesis - hypothesis that organisms will perform behaviour that restores the level of arousal to an optimum level • When an individual’s arousal level is too high, less stimulation is reinforcing, when it is too low, more stimulation is desired • Two forms of exploration related to arousal: Diversive Exploration & Specific Exploration o Diversive Exploration- is a response to understimulation (boredom) that increases the diversity of the stimuli the organism tries to come in contact with o Specific Exploration- is a response to overstimulation (usually because of a specific need, such as lack of food or water) that leads to the needed item, thereby decreasing the organism’s drive level • At optimum level of arousal: mid-range behaviour is organized and effective o Increasing arousal will produce increasingly effective behvaiour • Too little arousal in the suboptimal range: leads to ineffective behaviour because the person is not sufficiently motivated • Too much arousal outside optimal range: leads to disorganized & ineffective behaviour Perseverance: • Perseverance - the tendency to continue to perform a behaviour even when it is not being reinforced o They continue to perform even though their work is not regularly reinforced • When an organism’s behaviour is no longer reinforced, behaviour eventually ceases, or extinguishes • If behaviour is previously reinforced every time it occurred, extinction is very rapid • However, if it was previously reinforced only intermittently, behaviour persists for a long time o Intermittent reinforcement leads to perseverance, even when the behaviour is no longer reinforced • Extrinsic rewards - those that originate outside oneself • Intrinsic rewards - those that originate inside oneself • Overjustification Hypothesis - the superfluous application of extrinsic rewards to intrinsically motivated behaviour will undermine intrinsic motivation o Net result is a loss of intrinsic motivation o Ex: if a person has become motivated by extrinsic rewards and those rewards are no longer available, the person will no longer be motivated and we will witness a decrease in perseverance • Learned Helplessness - a response to exposure to an inescapable aversive stimulus, characterized by reduced ability to learn a solvable avoidance task; thought to play a role in the development of some psychological disturbances o Helplessness training lowers their expectation that trying to perform a task will bring success Eating ● need to eat shaped the evolutionary development of our species ● motivation to eat is aroused when there is a deficit in the blood's supply of nutrients and is satisfied by a meal that replenishes this supply ● people who exercise more, use up stored nutrient faster and so must eat more What Starts a Meal? - Physiological Factors ● physiological factors are responsible for eating ● Cannon and Washburn suggested that hunger results from an empty stomach ■ the walls of an empty stomach rub against each other producing hunger pangs ■ thirst was produced by a dry mouth - “spit and rumble theory” ■ removal of stomach does not abolish hunger pangs ● patients were interviewed whose stomachs were removed and their esophagi were attached directly to their small intestines ● these patients still felt hunger ● depletion of a body's store of nutrients is a more likely cause of hunger ● glucose is primary fuel for cell ● short-term reservoir stores carbohydrates (glucose is converted to glycogen and then stored) – located in the cells of the muscles and the liver ● long-term reservoir stores fats – consists of adipose tissue – found beneath the skin and in various locations ■ adipose tissue consists of cells capable of absorbing nutrients from the blood, converting them to triglyceride (fats) and storing them ■ keeps us alive during prolonged fasts ● once glycogen level is low in short-term reservoir, fat cells break down fats and release fatty acids and a carbohydrate called glycerol ● brain lives on glucose and body lives on fatty acid ● glycerol is converted to glucose so brain continues to be nourished ● difference between obese and normal weight person is the size of their triglycerides ● Glucostatic hypothesis – hunger occurs when the level of glucose in the blood becomes low ■ decrease in blood sugar is detected by glucose-sensitive neurons in the brain called “glucostats” ■ these detectors activate neural circuits that make a person hungry ● there are 2 types of nutrient detectors in the liver that measure the blood level of 2 primary nutrients, glucose and fatty acids ■ only activated in extreme cases when blood nutrient levels are severely depleted Cultural and Social Factors ● hunger can wax and wane according to a learned schedule ● environment affects hunger (ie. If we are with people who are eating then we will eat) What Stops a Meal? ● an hour passes before nutrients are absorbed from the intestines into the bloodstream ● primary cause of satiety is a full stomach ■ satiety is caused by entry of a sufficient quantity of nourishing food into the stomach ■ stomach must contain detectors that sense the presence of food and the chemical nature of its contents ● rats were allowed to eat until they were filled, some food was taken out of their stomach and were fed again, the rats ate approximately the same amount of food that was taken out ● chemical nature of food is important because if the food is nutritious eating will stop sooner ■ some rats were ingested with milk while some where ingested with water, the ones ingested with milk ate a lot less when fed 30minutes later ● direct infusion of glucose to hepatic portal reduced reduced how much and how long rat ate ● ob mouse has a low metabolism, overeats and gets really fat ■ ob gene, produces a protein called leptin ■ Leptin - secreted by fat cells that have absorbed a large amount of triglyceride; acts on hypothalamus to inhibit hunger ■ ob mice are unable to secrete leptin ■ if ob mice are given daily injections of leptin (even to the brain), their metabolism, body temperature and activity increase and so regain normal weight Obesity ● 14.9% of adults between 20 and 64 are obese ● 4-5 years after participating in a 15-week weight-loss program, fewer than 3% managed to maintain the weight loss they achieved during the program ● repeated bouts of weight loss and weight gain make future weight loss more difficult ● metabolic factors play an important role in obesity ● Metabolism – the physiological processes that take place in an organism ● people with an efficient metabolism have calories eft over to deposit in long-term reservoir making them more vulnerable to become obese ● people with inefficient metabolism can eat a lot without getting fat ● obese people secrete leptin but have efficient metabolisms and overeat ● in order for leptin to reduce weight, brain must contain functioning leptin receptors ● some people do not respond normally to the presence of leptin in blood ● overgrown fat cells secrete high levels of leptin, but the effect the hormone produces in the brain is less intense than normal, so people overeat Anorexia Nervosa and Bulimia Nervosa ● Anorexia nervosa – disorder characterized by a severe decrease in eating ■ have an intense fear of becoming obese ■ exercise constantly ■ a lot due to media ■ suffer from osteoporosis, stop menstruating ■ loss of brain tissue ● Bulimia nervosa – disorder characterized by a loss of control of food intake ■ gorge themselves with food ■ then induce vomiting or use laxatives SEXUAL BEHAVIOUR Effects of Sex Hormones on Behaviour • sex hormones, secreted by testes and ovaries have effects on cells all over the body that promote reproduction • these hormones cause production of sperm, build up lining of uterus, trigger ovulation, and stimulate production of milk • also effect nerve cells in brain, affecting behaviour • sex hormones DON’T CAUSE behaviours • sex hormones affect people’s motivation to act in reproductive way Effects of Androgens • androgens such as testosterone important for male sexual development • testosterone causes male sex organs and brain to develop • prenatal effects of sex hormones aka organizational effects because they alter organization of sex organs and brain • unless testosterone is present, males can’t have erection and engage in sexual intercourse • such effects aka activational effects because hormone activates sex organs and brain that are developed • Davidson, Camargo and Smith (1979)performed double-blind study of
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