Why do people…?

by Valerie Starratt, PhD

4 minutes

Why do people do what they do?

Human behavior may seem complicated, but when you strip it down to its basic functions it’s much easier to understand than people tend to believe.

Why do people [insert behavior of interest here]?

It’s one of those questions that seems to thread itself through life, from our most mundane moments to our most extraordinary ones.

It’s also the question I have spent my entire career answering, and the question that bothers me the most when other people answer it. 

Mostly I’m bothered because the answers other people give are just so… unsatisfying. Often, people “explain” a behavior by giving it a name and pretending the name is an explanation, or the explanation they give is so overwhelmingly and unnecessarily complicated it can’t possibly be consistent with what we know about how humans as a species function. Or maybe the answer they give is fine, but leads to more questions than it answers. 

Now, I could go through and provide lists of terms and definitions and discussions of things like ‘levels of analysis’. But that’s not fun so I’m not going to do it. Instead, let’s walk through an example of a behavior and some of the different ways we could answer the question why.

Here’s an easy behavior to start with: why do people… eat cheeseburgers. 

Before anybody starts arguing with me, I know. Cheeseburger eating is not a universal behavior. Not everybody does it. But some people do, and if you follow me on the logic of why those people do you’ll be able to see how that logic can be applied to any behavior.

So, here we go. Why do people eat cheeseburgers?

The most obvious answer, I think, is that people eat cheeseburgers because cheeseburgers are tasty.

I’d argue that most red-meat eaters (human or otherwise) would agree that this is true. Cheeseburgers taste good. Just thinking about a big juicy cheeseburger can make your mouth water. So if people like eating foods that taste good, and cheeseburgers taste good, then people should like eating cheeseburgers.

This is one of those answers that isn’t wrong but, for me at least, is unsatisfying. It’s unsatisfying because it doesn’t tell us anything useful. Ok, people eat cheeseburgers because they’re tasty. Now I’m forced to ask, but why? Why are cheeseburgers tasty?

If my answer to a question of why immediately leads to another question of why, I find that to be an unsatisfying answer. So I keep following the why train until it ends. Like this.

Why do people eat cheeseburgers?

Because they’re tasty and people like to eat tasty foods.

Why are they tasty?

Because they’re high in fat and calories.

Why do people find high fat and high calorie foods tasty?

Because fat and calories are physiologically valuable. 

Food is fuel, and for the vast majority of the human experience food has been scarce and costly to secure. Even today, billions of people worldwide live with some level of food insecurity. 

Why does that matter? Because any animal that doesn’t know when it’ll be able to eat again would be well served by choosing calorie dense foods that provide more energy to sustain them for longer so they can survive to a next meal. 

This isn’t to say there haven’t ever been people who inherently preferred low calorie foods over high calorie foods. But it does mean that, in times of food scarcity, a preference for low calorie foods would have been detrimental. Anyone who had a choice between a high calorie food and a low calorie food and chose the low calorie food, and then found themselves without an easy next meal, had a disadvantage compared to someone who had chosen the high calorie food. They literally might not have survived. At least, they had less chance of surviving (and passing down their low-calorie-food preferring genes) than the person who chose the more calorically dense food. 

So, in short: people today eat cheeseburgers because we are the descendants of those who demonstrated a preference for calorically dense foods and, because of that preference, outsurvived those without such a preference.

As a reminder, the beginning of this answer started with “because cheeseburgers are tasty”. This obviously isn’t the only way to answer the question of why people eat cheeseburgers. I could have said something like, because cheeseburgers are convenient. In the U.S., at least, burgers are both readily available and comparatively inexpensive. 

But then we have to get back on the Why Train.

Why are cheeseburgers so convenient?

Because businesses realized people would buy burgers and they could make money by selling burgers.

Why would people buy burgers?

And we’re back to the tasty and high calorie thing.

What if my original answer to why people eat cheeseburgers was because they are a familiar food and people like to eat things they find familiar? 

Fine, but again… why? Why are cheeseburgers a familiar food? Because most Americans are routinely exposed to burgers over the course of their lives. Why? Because they’re tasty and businesses realized they could make money selling them.

No matter where we start our answer, if we dig deep enough we always come around to the ultimate answer. The answer that provides a real, meaningful, functional explanation of the behavior. 

Why do we care about getting to a real, meaningful, functional explanation of a behavior?

Because if we understand a behavior, and I mean really understand a behavior, we can predict it and we can modify it. We can predict who is likely to engage in a behavior, when they are likely to engage in that behavior, and increase or decrease the likelihood of particular people under particular circumstances engaging in that behavior.

Who wouldn’t want to be able to do that?