When we think about the challenges of saving for retirement, psychology might not be the first thing to come to mind. If you're anything like me, the problem may have more to do with paychecks that can't cover all those tempting airfare purchases.

But as it turns out, our minds have a lot to do with why half of Americans aren't saving for retirement. Specifically, we may be falling victim to a common human cognitive error known as the "present bias."

A pensive man has the words now and later written in circles behind him. The now circle is surrounded by sunbursts and has an arrow pointing to the man.

Image source: Getty Images.

How the present bias makes it that much harder to save for retirement

Present bias is the common human tendency to place more value in immediate rewards than in those that will come in the distant future. In a 2011 experiment, UCLA professor Hal Hershfield demonstrated present bias in action. Hershfield showed college students photos of themselves that had been digitally doctored to reflect what they might look like at age 70. He found that students who were asked to "look their older self in the eye" would stash a much larger portion of a theoretical $1,000 windfall into a retirement account -- $172, as opposed to just $80 among the control group, on average. In forcing some subjects to confront their older selves, the exercise helped to counteract the cognitive error by making the future a bit more tangible.

If you, too, struggle with present bias, that's OK -- because once you recognize the error, you can take steps to correct it. For starters, you could try to emulate Hershfield's findings yourself: download one of those "age me" apps, like Oldify, and confront your mortality through your smartphone. Who knows? Staring your saggier self in the eye could be a great motivator (though it may also just make you giggle).

If you're looking for some more practical advice, then it would be wise to come up with, and frequently revisit, a detailed retirement plan that includes specific goals about how you plan to spend your end-of-life income and newfound leisure time. Put it somewhere where you'll see it often. This will help you envision your future self and the lifestyle you want that person to have.

How to save for retirement, no matter how old you are

Psychological motivation is important, of course. But when push comes to shove, your mindset isn't what pads your nest egg. Saving for retirement takes a conscious effort and a bit of know-how. But no matter how far away you are from that fateful date, there are plenty of simple ways to go about it.

1. Take advantage of your company's 401(k) match. If your employer offers a 401(k) plan, you ought to be contributing -- and that goes double if the plan comes with a match. While 1% to 3% of your paycheck might not seem like a lot, an employer match is essentially free money -- and the power of compound interest means those small contributions will add up exponentially over time.

2. Self-employed? Carefully consider your options. If you're an independent contractor or small-business owner, then a traditional, employer-sponsored 401(k) might not be an option. But Roth, traditional, and SEP IRAs still make it possible to get a leg up on your retirement planning. There's even such a thing as a 401(k) for the self-employed!

Each of these accounts has its own drawbacks and benefits, as well as specific rules for maximum contributions, taxation, and required distributions. Be sure to do your homework to figure out which type of self-employment retirement plan is right for your own financial situation.

3. Automate, automate, automate. Saving for retirement -- or any financial goal, for that matter -- is a whole lot less painful when you don't have to think about it. While 401(k) contributions are automatically deducted from your paychecks, if you're funding a separate retirement account, you may have to do it manually. Take your biased brain out of the picture entirely by setting up an automatic weekly or bi-weekly deposit. Just don't forget to get in there once in a while and allocate your assets.