Think about some of the things that you do every day. You eat food, usually because you’re hungry. You drink water, usually because you’re thirsty. And you sleep, usually because you’re tired. These are all ways of getting replenished, of getting yourself back to a state where you’re sufficiently nourished and well-rested. These are also the fundamentals of Clark Hull’s drive reduction theory of human behavior.
Clark Hull developed the drive reduction theory when he was working as a professor at Yale University alongside one of his most well-known graduate students named Kenneth Spence. He was primarily inspired by the theory of conditional reflexes posited by Ivan Pavlov, but also drew from John Broadus Watson’s theory of behaviorism. Hull’s theory of drive reduction states, in essence, that all human behaviors are caused by drives that result from a deviation from homeostasis. When you’re hungry, you’re out of homeostasis, and so you have the drive to eat. When you haven’t slept enough, you’re out of homeostasis, and so you have a drive to sleep.
Many parts of Hull’s drive reduction theory make a lot of logical sense. Perhaps if you found yourself in a perpetual homeostatic state (never hungry, never thirsty, never tired, always comfortable), you probably wouldn’t have any drive to do anything at all. That makes total sense within the framework of this theory. However, while Hull’s theory was a major driving force in the field of psychology for some time, modern criticisms have brought to light a couple of glaring flaws in it.
The Conditioning and Reinforcement Framework
Much like the other behaviorists of his time, such as Pavlov and Watson, Clark Hull sought to explain human behavior through conditioning and reinforcement. Conditioning is a type of learning in which a stimulus becomes increasingly effective at evoking a response. Reinforcement is the process of encouraging a certain pattern of behavior.
In a very simplistic example, imagine that you’d never been thirsty before. Then, one day, when you become thirsty, you decide to walk over to the sink and get a drink of water. When you have that drink of water, you no longer feel thirsty, and so you learn to associate drinking water with relieving your thirst. The next time you feel thirsty, you go to the sink again, and again the drink of water relieves your thirst. Thus, the behavior of going to the sink when you’re thirsty has been reinforced.
In speaking about conditioning and reinforcement, Clark Hull once said, “When survival is in jeopardy, the organism is in a state of need (when the biological requirements for survival are not being met) so the organism behaves in a fashion to reduce that need.”
In the framework of this theory, that state of need would be the stimulus, while the actions taken to reduce that need would be the behaviors that are being encouraged through conditioning and reinforcement.
The Drive to Homeostasis
The purpose of all human behavior, argued Hull, was to return the body to homeostasis, which is a state of equilibrium in which all of the human being’s physiological needs are met. Being in homeostasis would mean that you’re not hungry, not thirsty, not tired, not uncomfortable, and everything is going just right with your body.
However, over time, the human body needs to replenish itself. When the biological needs of the human body are not met, it creates tension, or drive. According to Hull, these drives are at the root of all motivation.
For example, if you haven’t eaten anything in a while and your body is short on the nutrients that it needs, you’re going to feel hungry. Hunger is a point of tension, so your body will seek to relieve that tension. You will develop a drive to return to homeostasis, which would be the state of not feeling hungry anymore. That drive to not be hungry anymore will motivate you to take action. You will go hunting if you’re a caveman. You will go search through your refrigerator if you’re a 21st-century American.
For Hull, the drive to relieve tension and return to homeostasis was at the root of all behavior, not just simple things like drinking water or eating food. The life of a human being is therefore just a cycle of certain needs being depleted, then developing a drive to replenish those needs, then engaging in behaviors to replenish those needs, then returning to homeostasis, and then having those same needs depleted once again, thus restarting the cycle. As we humans engage in different behaviors to replenish our needs, we find which ones work the best, and we are more likely to engage in those behaviors again.
The Formula for Motivation
Clark Hull went so far as to create an actual mathematical formula that he hoped would be able to predict a human being’s motivation, given a set of certain definable factors. This formula wasn’t really meant to have actual numbers plugged into it, but more to explain how certain factors related to each other. Here is the formula:
sEr = V x D x K x J x sHr – sIr – Ir – sOr – sLr
- sEr – excitatory potential, or the likelihood that an organism will produce a response
- V – stimulus intensity dynamism, or how much influence a particular stimulus has
- D – drive strength, or the degree to which the biological need has been depleted
- K – incentive motivation, or the size or magnitude of the goal to be undertaken
- J – the delay before the organism is allowed to seek reinforcement
- sHr – habit strength, or the amount of previous conditioning the organism has had
- sIr – conditioned inhibition, or the lack of previous reinforcement
- Ir – reactive inhibition, or fatigue
- sOr – random error
- sLr – reaction threshold, or the smallest amount of reinforcement needed to learn
For obvious reasons, Hull’s theory was viewed as being overly complicated by many of his contemporaries. However, this method of explaining behavior in a mathematical and formulaic way made a major impact on the field of psychology and has been used by many psychologists since Hull’s time.
Criticisms of the Drive Reduction Theory
As you can probably tell by now, the drive reduction theory works very well for simple behaviors such as eating, drinking, or sleeping. However, as we start to look at more complex behaviors that humans engage in, the drive reduction theory seems less universally applicable. As humans, we engage in quite a few behaviors that don’t fulfill physiological needs and even many behaviors that increase our physiological states of depletion.
For example, take activities like snowboarding or skateboarding. These activities don’t help us fulfill any physiological needs. In fact, they are quite dangerous and they actually make us tired and thirsty and hungry.
As another example, many people will eat food even when they aren’t hungry or drink when they aren’t thirsty. If the sole purpose of human behavior is to stay as close as possible to a state of homeostasis, why would humans engage in any of these types of behaviors? These types of behaviors just simply do not fit into the framework of the drive reduction theory.
Perhaps the greatest flaw in the drive reduction theory is that it fails to account for secondary reinforcers, the stimuli that encourage a behavior because they have been associated with a primary reinforcer.
For instance, if you get a dog to do a trick and then give him a treat and pat him on the head, he will start to associate getting patted on the head with getting a treat. The behavior being encouraged in this scenario is the trick, the primary reinforcer is the treat, and the secondary reinforcer is the pat on the head. However, you should notice that getting a pat on the head does nothing to help fulfill the dog’s physiological needs. This is precisely where the drive reduction theory breaks down.