I like to think I'm a pretty smart guy--but we all do stupid things sometimes.

For example, I graduated near the top of my law school class, but I sometimes question how smart it was to go to law school in the first place. And I'm reminded of the hour or so I spent not long ago searching for my glasses--only to realize they were perched on the brim of my baseball cap.

Most of us could a little more brainpower. Writing in The New York Times, Richard Friedman, a professor of clinical psychiatry at Weill Cornell Medical College, examined the current state of scientific thought on whether we can truly train ourselves to be smarter.

As Friedman points out, it's "hardly an idle question considering that cognitive decline is a nearly universal feature of aging." The brain shrinks physically once we hit age 55, and about 11 percent of people over 65 wind up exhibiting signs of Alzheimer's disease.

Before we dive in, there's a bit of hair-splitting in brain science you ought to be aware of. It's that the goal is defined as enabling people to achieve their personal maximum intelligence--as opposed to increasing it. But either way, you'd be getting smarter.

With that in mind, here are seven keys to understanding what science says you can (and can't) do to increase your intelligence.

1. Brainteasers work--but maybe just at making you better at brainteasers.

I'd expect some pushback on this one, because brain-training games are a multibillion-dollar industry. However, Friedman cites a British study that broke a group of students into four classes and tested how well they performed on tests after various forms of brain training and games.

"Although improvements were observed in every cognitive task that was practiced," he writes, "there was no evidence that brain training made people smarter. Scores on the benchmark test, for which subjects could not train, did not significantly increase at the end of the study."

2. Except that they seem to work for older people.

There's a little bit of hope, however. Older participants in the study--those over 60 years old--showed more increase in performance than younger people. So, the researchers continued the experiment with older participants in a follow-up study that lasted a full year.

"Results of this follow-up study, soon to be published in a peer-reviewed journal, generally show that continued brain training helps older subjects maintain the improvement in verbal reasoning seen in the earlier study. This is good news because it suggests that brain exercise might delay some of the effects of aging on the brain," Friedman writes.

3. Believing you can improve helps--at least with younger brains.

Now, we get into some of the really cool data. When it comes to younger people especially, studies have shown that simply convincing them that they can improve their intelligence can create a self-fulfilling prophecy in which they perform better on intelligence tests.

"These findings appear to have profound implications for educating young people," Friedman writes, "because they suggest that a relatively simple intervention...can have a powerful effect: enhancing learning and motivation."

4. Physical exercise can help...

Seriously, when in life does physical exercise not help? In the case of developing brains, the idea is that it can promote the physical growth of neurons. Researchers for example tested the effects of resistance, aerobic, and balance exercises on groups of people who had "mild cognitive impairment," Friedman writes, with very interesting results.

"The researchers found that while both resistance and aerobic training groups improved equally on spatial memory," he writes, "only the women who did aerobic exercise improved on verbal memory, suggesting that different types of exercise might have specifically different cognitive benefits."

5. ...as does avoiding depression.

This might be one of the less-surprising things Friedman writes: Having major depressive episodes can negatively affect intelligence, and can even cause parts of the brain to shrink, and decrease the presence of a protein called "brain-derived neurotrophic factor, or BDNF"

The solution could potentially lie in antidepressant medication, which, he writes, "aside from making people feel better...can block the depression-induced drop in BDNF."

6. But as for other drugs--it's complicated.

Some of us might welcome the science-fiction solution--the development of a simple pill that increases brain size and intelligence. We're not there yet. However, drugs like Ritalin and Adderall can make people feel more intelligent by increasing focus and making "the world feel more interesting by releasing dopamine in key brain circuits," Friedman says.

Beyond that, the jury is out, he writes, although there is some evidence that these drugs can make it easier to "to recall previously learned information--an effect that might confer some advantage in the real world."

7. Having good human relationships increases brainpower.

The one sure thing that seems to help increase brainpower, he writes, is having better relationships with other people. For example, a Harvard professor tracked 17,000 people who were at least 50 years old, over a six-year period--periodically giving them intelligence tests along the way.

"The results showed that people with the highest level of social integration had less than half the decline in their cognitive function of the least socially active subjects," Friedman writes.

So where does all this leave us? It's pretty simple, Friedman concludes: "Forget the smart drugs and supplements; put on your shorts and go exercise. If you're 60 and up, consider brain training. And do it all with your friends."