Habitual routine may explain most people's preference for a morning cup of joe to start the day.

Editor’s Note: The views expressed in this commentary are solely those of the writers. CNN is showcasing the work of The Conversation, a collaboration between journalists and academics to provide news analysis and commentary. The content is produced solely by The Conversation.

The Conversation  — 

If you’re like many Americans, you probably start your day with a cup of coffee – a morning latte, a shot of espresso or maybe a good ol’ drip brew.

A common explanation among avid coffee drinkers is that we drink coffee to wake ourselves up and alleviate fatigue.

But that story doesn’t completely hold up. After all, the amount of caffeine in a cup of coffee can vary wildly. Even when ordering the same type of coffee from the same coffee shop, caffeine levels can double from one drink to the next. And yet, we coffee drinkers don’t seem to notice.

So what else might be driving us in our quest for that morning brew?

That’s one question we set out to answer in our recent research. The answer has far-reaching implications for the way we approach major societal challenges such as diet and climate change.

As behavioral scientists, we’ve learned that people often repeat everyday behaviors out of habit. If you regularly drink coffee, you likely do so automatically as part of your habitual routine – not just out of tiredness.

But habit just doesn’t feel like a good explanation – it’s unsatisfying to say that we do something just because it’s what we’re used to doing. Instead, we concoct more compelling explanations, like saying we drink coffee to ease our morning fog.

This reluctance means that we fail to recognize many habits, even as they permeate our daily lives.

READ MORE: What you do every day matters: The power of routines

Unpacking what lies behind habits

To test whether people underestimate the role that habit plays in their lives, we asked more than 100 coffee drinkers what they think drives their coffee consumption. They estimated that tiredness was about twice as important as habit in driving them to drink coffee. To benchmark these assumptions against reality, we then tracked these people’s coffee drinking and fatigue over the course of one week.

Enthusiasm about starting a new workout regimen may falter if you fall back on  habits that nix exercise.

The results starkly diverged from our research participants’ explanations. Yes, they were somewhat more likely to drink coffee when tired – as would be expected – but we found that habit was an equally strong influence. In other words, people wildly overestimated the role of tiredness and underestimated the role of habit. Habits, it seems, aren’t considered much of an explanation.

We then replicated this finding in a second study with a behavior that people might consider a “bad” habit – failing to help in response to a stranger’s request. People still overlooked habit and assumed that their reluctance to proffer help was due to their mood at the time.

The gap between the actual and perceived role of habit in our lives matters. And this gap is key to understanding why people often struggle to change repeated behaviors. If you believe that you drink coffee because you are tired, then you might try to reduce coffee drinking by going to bed early. But ultimately you’d be barking up the wrong tree – your habit would still be there in the morning.

READ MORE: Research-based tips for adopting and sticking to new healthy lifestyle behaviors

Why habits are surprisingly difficult to change

The reason that habits can be so difficult to overcome is that they are not fully under our control. Of course, most of us can control a single instance of a habit, such as by refusing a cup of coffee this time or taking the time to offer directions to a lost tourist. We exert willpower and just push through. But consistently reining in a habit is fiendishly difficult.

To illustrate, imagine you had to avoid saying words that contain the letter “I” for the next five seconds. Pretty simple, right? But now imagine if you had to maintain this rule for a week. We habitually use many words that contain “I.” Suddenly, the required 24/7 monitoring turns this simple task into a far more onerous one.

We make a similar error when we try to control