Here's a perfectly rational way to make tough decisions: gather all the evidence about the alternatives, analyze the pros and cons, judiciously weigh all those factors, and finally come to a sensible decision.

It sounds so straightforward, but as anyone who has ever wrestled with a tough call full of complicated trade-offs can tell you, it's anything but. Why is that? Among other reasons because your brain really isn't built to be rational.

Human psychology is shot through with biases and shortcuts designed to help us make good enough decisions fast (like the ones our ancestors had to make to survive being chased around the savannah by a host of terrifying toothed creatures). But when it comes to more deliberately paced, complex modern dilemmas, these same cognitive quirks often trip us up.

It's human nature to obsess about the negative.

Take one recently hightlighted by recent research out of the Stanford Graduate School of Business, for example. Humans, it turns out, are really bad at weighing pros and cons. Negatives, it seems, just affect us more.

"Suppose you are evaluating a person -- for example, a job candidate -- and you make a list of his or her positive and negative qualities," explained Stanford marketing professor Zakary Tormala to Insights by Stanford. "Even assuming you come up with positives and negatives that are equally relevant and compelling, the negatives tend to carry more weight."

That means that even if an alternative (say a potential hire, a hotel we might book, or a new career option) is chock full of upsides, just one or two stray negative comments, reviews or possible downsides can paralyze us with doubt. On the other hand, adding one or two glowing reviews to an otherwise negative picture doesn't generally make us rethink our poor opinion of an alternative.

Marketers have used this truth for decades, knowing that sowing just a few seeds of doubt about a competitor can lead customers into such a mental muddle they'll refuse to buy its products. But when it comes to making optimal decisions for your own life or business, this bias for negativity isn't so useful.

How to fix the traditional pros-and-cons list

How do you maneuver around this built-in brain quirk? The first step is simply keeping in mind it exists. "It's possible that you could resolve your own internal conflict more quickly, and thus take action more swiftly, by recognizing that negative information has a stronger effect on ambivalence than does equivalent positive information," suggests Tomala.

So the next time one random comment about the cleanliness of a hotel that's otherwise garnered rave reviews is making you rethink booking a room, or a small concern about airport connectedness of the weather in March is holding you back from taking the plunge and moving to a new city, remember this study and weigh your pros and cons list again, this time putting a finger on the scales for the positives.

By mentally demoting the importance of the negatives and highlighting the pros, you can correct for your natural bias toward negativity and make more sensible choices.