April 15, 2014 12:01 AM EDT

Stress is not all bad. I often remind my PhD students that some degree of stress can be a useful motivator for increased performance and productivity. (Have to present your research project next month? Better get started!) The problem, of course, is that many of us live with too much stress, and it seems that every year we discover new levels of busy-ness, new ways of falling behind, and new heights of stress.

The biggest stressors in our lives — nearing deadlines, dysfunctional relationships, difficult coworkers — are relatively clear. And although we don’t always know exactly what to do about them, their existence and their impact on our well being is pretty straightforward. Less clear, however, is the profound effect of the smaller stressors — those tiny nagging annoyances that accumulate. To fully appreciate the effects of (seemingly) small stressors, consider this:

In a study published in 1999, researchers Baba Shiv and Alexander Fedorikhin asked one group of participants to remember a two-digit number (something like, say, 35) and another group of participants to remember a seven-digit number (say, 7581280). In order to get paid for the experiment, all of these participants would have to repeat the number to another experimenter who was waiting for them at the other end of a long corridor. And if they didn’t remember the number? No reward. The researchers wondered whether being under a low cognitive load (2 digits) vs. a high cognitive load (7 digits), would influence the participants’ ability to think and make good decisions.

With their respective numbers in mind, down the corridor they went. As the participants walked down the hall toward their destination, they unexpectedly passed a cart displaying pieces of rich, dark chocolate cake alongside bowls of colorful, healthy fruit. As participants walked by the cart, another experimenter stopped them in their tracks to offer them one of the two snacks.

What decisions did participants make, and did these decisions depend on whether they were under a low or high cognitive load? Was their choice of cake or fruit related to the number they had in their heads? The results showed that those under a high cognitive load condition (think about those of us with large to-do lists, or many things on our minds) chose the cake much more frequently than the participants in the low cognitive load condition. With their higher-level faculties preoccupied, the seven-digit group was less able to overturn their instinctive desires, and many more of them ended up succumbing to the instantly gratifying chocolate cake.

A second, more timely, example of the impact that seemingly small stressors have on our decisions, is based on an analysis carried out by Donald Redelmeier and Christopher Yarnell. Examining car accidents over a 30-year period, they found that on April 15th (which is Tax Day in the U.S.), Americans have about a 6% increase in fatal road crashes. This increase in fatalities puts tax days in the same risk category as Super Bowl Sunday, although presumably the effect is due to alcohol in one case and stress in the other (though from the data we can’t be certain).

Together, the controlled cognitive load experiment and the analysis of fatalities in car accidents suggests that our cognitive capacity is dangerously low, and that even relatively small external interventions can tax us — and they can tax us to a level that is hard to believe. The results also suggest that you should be extra careful driving this April 15th.

Beyond the questions of cake and driving on Tax Day, the applications of these findings to our daily life are important. If (seemingly) small stressors can derail our decisions to such a degree, what should we expect in a world where people keep 100 to-dos in one list, 50 in another, trying to juggle home and work responsibilities, while being surrounded by multiple electronic devises that alter us that all kinds of important things are happening (someone liked a picture we posted on Facebook!)?

Could it be that the same wonderful technological advances also tax our limited cognitive ability and attention? I suspect so. I suspect that many of us live a mindset that is equivalent to trying to remember a 27-digit number while driving on a day that is both Tax Day and Super Bowl Sunday.

What can we do about this? The answer is technologically complex but conceptually simple. The first step is to realize our limitations, and the second is to design tools for the Homer Simpson in each of us. We need devices, alerts, to-do lists and calendars that don’t tax our limited cognitive capacity, but free some of it instead. We need tools that decrease our stress, and we need tools that allow us to make better decisions. And until we get these, lets drive extra carefully this April 15th.

Dan Ariely is the James B. Duke Professor of Psychology and Behavioral Economics at Duke University and the author of Predictably Irrational and, most recently, The (Honest) Truth About Dishonesty: How We Lie to Everyone — Especially Ourselves.

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