Why are people motivated to do what they do? One early premise, the drive reduction theory, attempts to explain some of the basics.

Picture this: You’re working remotely on your laptop when, on autopilot, you go to your kitchen, grab a glass, and fill it up with water.

No one needed to tell you to do it. You don’t remember being consciously aware of the thought to get up and get hydrated. Yet, here you are, standing at the sink.

What caused this behavior?

Put forward by U.S. psychologist Clark Hull in the 1940s, drive reduction theory or drive theory of motivation was conceptualized as a way to explain human learning and motivation.

It draws inspiration from Charles Darwin and Ivan Pavlov’s research on conditioning, among other notable names in psychology.

Drive reduction theory centers around the idea of homeostasis. That is, humans are drawn to behaviors that can help them achieve physical and mental equilibrium.

The core premise is that motivation comes from your biological needs.

While this theory was popular in the 1940s and 1950s, it’s no longer considered a viable explanation for human behavior.

The term “drive” refers to the tension or discomfort you experience when your biological needs kick into high gear, like a mental itch that needs to be scratched.

In the table below, the middle column represents the drive that compels you to take action. The first column is the equilibrium you reach with the action shown in the third column.

HomeostasisBiological driveReduction behavior
SatiatedHungryGrabbing an apple
HydratedThirstyDrinking a glass of water
Balanced temperatureFeeling coldPutting on a jacket
NeutralitySexual arousalHaving sex or masturbating

Hull suggested that if the reduction behavior — like eating, drinking, or having sex — brings you back to a state of homeostasis, you’re more likely to repeat that behavior again.

This is a form of positive reinforcement (more on that in a bit).

Hull used a math formula, called the mathematical deductive theory of behavior, to try to predict human behavior:

sER = V x D x K x J x sHR – sIr – Ir – sOr – sLr

Got that? OK, so here’s what it means:

  • sEr: excitatory potential, which is how likely you are to respond to an internal stimulus
  • V: stimulus intensity dynamism, which means that some types of stimuli may drive you more than others
  • D: drive strength, which is how strong your biological need is, such as being a little parched versus peeing dark yellow
  • K: incentive motivation, or how big the goal you’re trying to achieve is
  • J: how long you have to wait before you can try the reduction behavior again
  • sHr: habit strength, which is how many times you’ve done this behavior before
  • slr: conditioned inhibition, which is how many times the behavior has not given you the result you desired
  • lr: reactive inhibition, which is a fancy way of describing your fatigue
  • sOr: random error
  • sLr: reaction threshold, which is how little reinforcement it takes to learn a new behavior

A simpler equation

Hull was criticized by other psychologists for having an overly complex formula. If the original seems too confusing, consider drive reduction theory in just two parts:

  • internal stimulus + response = drive reduction
  • drive reduction = repetition
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Hull was a behaviorist, a popular approach to understanding motivation.

Put simply, behaviorism (also known as behavioral psychology) says that you learn by interacting with your environment.

The key concepts include:


Your arousal about life is part of what motivates you to act. As your arousal levels change, you naturally take steps to get back to your “optimal” level, whatever that is.

If your arousal level is low, for example, you may book a ticket to a bucket list destination to find adventure and stimulate your senses.

On the other hand, if your arousal level is high, you may try to carve out some alone time and catch up on a good book.


Homeostasis is when any organism regulates its internal environment, like body temperature, hydration levels, and blood sugar level.

In psychology, homeostasis can also refer to keeping your mental state balanced.

Conditioning and reinforcement

Conditioning means learning about the world through reinforcement, for better or for worse. For example, studying to get an A on a test (positive) or getting bitten by a dog (negative).

Positive reinforcement centers around two groups of drives:

  • primary drives: thirst, hunger, sex
  • secondary drives: money, social approval

Since the 1950s, newer research has pointed out a number of flaws within the drive reduction theory, which is why it’s all but ignored today.

Some critics said that, if humans are wired for homeostasis, it doesn’t explain why people participate in risk-taking behaviors, like bungee-jumping or scuba diving.

Along a similar vein, if humans are only motivated by biological needs, then it doesn’t explain why people sometimes behave outside of those parameters, like when you grab a bag of chips even though you aren’t hungry.

And what about how people are motivated by money, a secondary drive? If drive reduction theory states that we’re only wired to reduce primary drives (thirst, hunger, sex), then it doesn’t explain why we’ll work harder for better pay.

Despite criticism, Hull’s work helped spark other theories of learning and motivation.

In 1956, for example, one study found that incentives had a similar effect as drive reduction, which paved the way for the incentive theory. This states that, sometimes, you are motivated to do things because of rewards.

Then there’s psychologist Abraham Maslow, who presented his hierarchy of needs as an alternative to drive reduction theory — and it’s still in use today. It helped form our understanding of humanistic theory, which suggests that some of what we do is for cognitive reasons.

Though Hull’s work may have been called untenable (it can’t be supported), it certainly inspired other experts to keep digging and made valuable contributions in this regard.

Drive reduction theory attempted to offer a simple explanation for why we grab food when we’re hungry, or water when we’re thirsty.

However, we now know that human beings are far more complicated.

It’s no longer a popular theory because it can’t account for why we engage in complex behaviors when there’s no biological necessity for, among other reasons.

Still, drive reduction theory led to a number of alternatives that formed a deeper understanding of human behavior, learning, and motivation.