Oct. 16, 2025

PSY 101    Class 22: Motivation I • Theories & Hunger as Motivated Behavior (Outline)

Motivation  Goal-Directed Behavior

Why do you and I do the things that we do???
What is it that you want or desire?

Motivational Theories and Concepts

1. Drive Theories ("push" theories) homeostasis (balance) allostasis (process of reaching balance by physical or behavioral change) Drive = (a) internal state of tension which (b) motivates an organism (c) to act to reduce the tension

2. Incentive Theories ("pull" theories) Incentive = external goal which can motivate behavior

3. Evolutionary Theories maximize reproductive success, e.g., dominance affiliation (need for belonging)

4. Diversity of Motivation

Biological	Social
Originate in bodily need Hunger Thirst Sex Sleep, etc.	Originate in social experiences Achievement Affiliation Nurturance  Play

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

Multifactorial causation!

Biological Factors in the Regulation of Hunger

           

A. Brain: Interconnected neural circuits in the hypothalamus

• Lateral Hypothalamus (LH): Initiate eating
• Ventromedial Hypothalamus (VMH): Stop eating
• Arcuate Nucleus: Dual set of neurons: start & stop
  
• Paraventricular Hypothalamus (PVH): modulation of hunger
  

• Neurotransmitters:
  
• neuropeptide Y (↑ carbs) & serotonin (↓ fats, food)
  

B. Digestive & Hormonal Regulation

Signals from stomach

Hormones

• Ghrelin
• CCK (cholecystokinin)
• Insulin
• Leptin
  

Environmental Factors A. Food Cues: Incentives Palatability Quantity Variety (Sensory-specific satiety) Presence of Others Stress Exposure to Cues
Arachnids as food	B. Learning Innate (in-born) Observation of others eating

The Roots of Obesity: Eating & Weight

• Obesity
• Body Mass Index (BMI) = weight (in kgms)/height (in m.) squared
• 18.5 to 24.9 = normal
  
• 25-29.9 = overweight
• 30-39.9 = obese
• over 40 = morbidly (severly/extremely) obese

According to the CDC in 2021-2023, 40.3% of adult Americans are obese (= ca. 105 million) and 9.4% of adults were severely obese (= ca. 24.5 million 

 





Why? Factors in Obesity in US

A. Genetic Predisposition: Moderately high levels of heritability for weight in men & women



B. Excessive Eating & Inadequate Exercise (see D. below as well)



C. Inadequate Sleep

D. Socio-economic Factors in Industrialized/Developed Nations [Not in textbook; ]

• In industrialized nations: individuals expend more energy than in poorer settings, but consume even higher levels of calories.
• Diets in industrialized nations: ultra-processed foods = high in calories ["energy dense"], very good tasting [flavorings & textures]
  

E. The Notion of a "Set Point"

 

This page was originally posted on 10/16/03