Oct 19, 2016
| PSY 101
Motivation I: Theories & Hunger
as Motivated Behavior
Motivation Goal-Directed Behavior
WHY DO YOU DO WHAT YOU DO ???
Motivational Theories and Concepts
1. Drive Theories ("push")
Walter Cannon: Organisms seek to maintain homeostasis (a state of physiological equilibrium, balance, or stability). NOT IN BOOK: The process of achieving homeostasis by means of physiological or behavioral changes is called allostasis (i.e., using multiple different methods to reach equilibrium ["allo-" to achieve balance "stasis"] Temperature = 98.6 degrees ==> too high leads to sweating and too low leads to shivering
Drive = (a) internal state of tension which (b) motivates an organism (c) to act to reduce the tension For example, going without food or drink for a period of time causes us to feel an internal craving for either food or liquid Cannot explain all behavior, e.g., people often eat when they are not hungry
2. Incentive Theories ("pull")
- Incentive = external goal which can motivate behavior
- For example, the smell of a wonderful dinner cooking, recognition for a job well done by your boss, getting on the Dean's List, earning a lot of money so that you can buy what you want
3. Evolutionary Theories
- Evolution favors those behaviors which maximize reproductive success (i.e., attracting a mate & passing genes on to offspring)
- dominance by males attracts females who judge themselves better protected
- affiliation (need for belonging) assists in raising offspring by bringing together more helpers
4. The Two Types of Motivations
Originate in bodily need
- Sleep, etc.
Originate in social experiences
- Achievement (need to stand out, do well, excel)
- Affiliation (need to belong, to be bonded with others)
- Nurturance (need to nourish & protect others)
- Play, etc.
Hunger & Eating
What can we say about the causes of Homer Simpson's insatiable appetite for doughnuts?
A very complicated set of interrelated & interacting forces & mechanisms
appears responsible for the final experience of hunger and eating.
I. Biological Factors
A. Brain: Interconnected neural circuits in the hypothalamus
- Lateral Hypothalamus (LH): damage causes animal to stop eating; hence, LH may normally play a role in initiating eating
- Ventromedial Hypothalamus (VMH): damage causes animal to eat excessively & gain weight; hence, VMH may normally play a role in stopping eating
- Arcuate Nucleus: Dual set of neurons = (1) responsive to hunger signals and (2) respond to satiety signals (satiety = feeling of being full, "enough")
- Paraventricular Hypothalamus (PVH): modulation of hunger (either increasing or decreasing)
- Neurotransmitters: neuropeptide Y (increases eating of carbohydrates if injected in PVH) and serotonin (decreases fat & food intake) in particular
B. Digestive & Hormonal Regulation
Glucose is a simple sugar & provides energy
- Glucostatic Theory: hunger is controlled by "glucostats" -- neurons in the brain which are sensitive to the amount of glucose in the blood.
- Liver also may send glucostatic information via the vagus nerve to the brain
- Stomach sends information about various states, e.g.,
- Stomach distention (how full stomach is) via vagus nerve
- Empty stomach produces hormone ghrelin which promotes stomach contraction & hunger
- Upper intestine releases the hormone CCK (= cholecystokinin) which signals satiety as well
II. Environmental FactorsOther Hormones
Insulin: hormone which allows glucose to be extracted from the blood
- Insulin increase leads to increase in hunger. Judith Rodin (1985) showed that just seeing or smelling food can cause insulin to be secreted
Leptin: hormone (discovered in the early 1990s) produced by fat cells in body and circulating in the bloodstream. It signals to the brain the size of the body. And, for most people when they have reached a certain body size, leptin decreases the urge to eat.These hormonal signals (the fluctuation of insulin, ghrelin, CCK, and leptin) converge on the hypothalamus (esp. the arcuate & paraventricular nuclei) to affect eating
A. Food CuesIncentive value of food
- Attractiveness of food increases hunger
- Good taste increases consumption
- Quantity: Availability of food generally increases eating
- In recent years, many foodstuffs have gotten larger and larger in size
- Sensory-specific satiety: If you eat a lot of the same food, the appeal of that food goes down. But, if there are many types of food, you will try more.
B. Learning: What foods do you adore? Despise? When did you learn to love or hate those foods?
- Innate (in-born) taste preference for high-fat foods and sweet foods
- Many other taste preferences come from experiences where they are paired with other pleasant tasting foods
- Observation of others eating, e.g., younger children more apt to taste food if adult does. We may also see negative reactions of others and develop similar aversions.
- Flickr Images of Fried Tarantulas
This page was originally posted on 10/16/03 and last updated October 19, 2016