Why Do Animals Do What They Do?

Michael D. Breed and Leticia Sanchez addressed this question by phrasing it in a different way: “What Functions of Living Systems Underlie Behavior?” How do outward signs line up with inner states? Animals have internal needs and sensory inputs and perceptions, so how do those transmute and translate into behavior?

How much are their decisions influenced by basic feelings like being hungry, horny, in pain or afraid? Based on what animals see, hear, smell, taste, etc. — how do they rate their options? If they do, there must be a ranking system. How can researchers learn what it is? Do animals weigh the viabilities and consequences of different behaviors, or just plunge right in?

The authors say that somehow, “Animals integrate these external and internal inputs to set their behavioral priorities.” Just like ours, their reactions to the world are informed by input from external and internal sources:

Specialized functions, like learning and memory, coordination of movement, and regulation of physiological functions are performed in different regions of the brain, and neural connections within the brain allow the transfer of information among these regions.

Different parts of the brain recognize information as useful; remember data from the past; and know what to do when presented with various types of information. Environmental data, in the form of sensory cues, comes in; neurotransmitters spread it around. The nervous system connects all those sources so they can act upon each other. The glands and organs of the endocrine system squirt hormones into the blood “to regulate behavioral responses, seasonal changes in behavior, mating, and parental care.” Meanwhile, intelligence continues to be gathered from the environment.

Baby, you can drive my car

All this information accumulates to serve innate drives as posited, like so much else, by Sigmund Freud. The drive theory of motivation is also known as the drive reduction theory, which is self-contradictory enough to induce confusion from the very start. They are the same thing.

The drive reduction theory was mainly developed by behaviorist Clark Hull. Drives must be reduced to achieve homeostasis, also known as equilibrium or balance. According to this mindset, drive reduction is the “primary motivation behind all human action.” On the website of the educational institution Harappa, an uncredited author speaks of the tension caused by unfulfilled biological needs:

As soon as there’s an unmet need within the body, a person starts behaving in a manner that allows them to address this need… [T]he reduction of the drive functions as a reinforcement of the behavior that helped the person to satisfy their unfulfilled need. Such reinforcement increases the likelihood of the person behaving in the same manner in the future to address that particular drive.

In 2001, Michael D. Breed asserted that drive theory had become ignored or scorned, until 1992 when it made a roaring comeback and everybody was talking about self-directed behavior (SDB) and body-focused repetitive behaviors (BFRBs) and all kinds of interesting things.

Your responses and feedback are welcome!

Source: “What Functions of Living Systems Underlie Behavior?,” Nature.com, 2010
Source: “Drive Theory Of Motivation: Meaning And Examples,” Harappa.education, 11/24/21
Source: “Displacement Behavior,” AnimalBehaviorOnline.com, 2001
Image by Mark Freeth/CC BY 2.0

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About Dr. Robert A. Pretlow

Dr. Robert A. Pretlow is a pediatrician and childhood obesity specialist. He has been researching and spreading awareness on the childhood obesity epidemic in the US for more than a decade.
You can contact Dr. Pretlow at:


Dr. Pretlow’s invited presentation at the American Society of Animal Science 2020 Conference
What’s Causing Obesity in Companion Animals and What Can We Do About It

Dr. Pretlow’s invited presentation at the World Obesity Federation 2019 Conference:
Food/Eating Addiction and the Displacement Mechanism

Dr. Pretlow’s Multi-Center Clinical Trial Kick-off Speech 2018:
Obesity: Tackling the Root Cause

Dr. Pretlow’s 2017 Workshop on
Treatment of Obesity Using the Addiction Model

Dr. Pretlow’s invited presentation for
TEC and UNC 2016

Dr. Pretlow’s invited presentation at the 2015 Obesity Summit in London, UK.

Dr. Pretlow’s invited keynote at the 2014 European Childhood Obesity Group Congress in Salzburg, Austria.

Dr. Pretlow’s presentation at the 2013 European Congress on Obesity in Liverpool, UK.

Dr. Pretlow’s presentation at the 2011 International Conference on Childhood Obesity in Lisbon, Portugal.

Dr. Pretlow’s presentation at the 2010 Uniting Against Childhood Obesity Conference in Houston, TX.

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