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Oct 19, 2016
  
  PSY 101    [Psychology
                  Images] Motivation I: Theories & Hunger as Motivated Behavior

Motivation => Goal-Directed Behavior

WHY DO YOU DO WHAT YOU DO ???


Motivational Theories and Concepts

Body temperature is homeostatic1. 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")

          


    3. Evolutionary Theories

          


    4. The Two Types of Motivations

     Biological Social

    Originate in bodily need

    • Hunger
    • Thirst
    • Sex
    • 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

    [Homer_Donut1]
    What can we say about the causes of Homer Simpson's insatiable appetite for doughnuts?
    [Homer_Donut2]


    A very complicated set of interrelated & interacting forces & mechanisms
    appears responsible for the final experience of hunger and eating.

    I. Biological Factors

    [Brain
                    Hypothalamus]   hypothalamus   Hypothalamus (Visible Human Female)

    A. Brain: Interconnected neural circuits in the hypothalamus

    • hypothalamic
                          control of eatingLateral 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
    Insulin Other 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

    II. Environmental Factors

    A. Food Cues

    Bread in a bakeryIncentive value of food

    fried tarantulas
                in CambodiaB. Learning: What foods do you adore? Despise? When did you learn to love or hate those foods?






     

    This page was originally posted on 10/16/03 and last updated October 19, 2016