It's both appealing and disturbing to think that taking a pill could boost someone's brainpower to make them "smarter."

Films like "Limitless" and "Lucy" create fantasies of cognition-enhancing drugs that practically provide superpowers. In the real world, college students and finance workers have been known to cram while hopped up on medications like Adderall and Ritalin, pharmaceuticals normally used to treat attention-deficit hyperactivity disorder, or ADHD.

But data has historically been mixed when researchers have investigated the effect of those drugs on mental capacity. Some studies have found so-called smart drugs to have cognitive benefits, but others have shown they don't make a difference for many people, especially those of average or above-average intelligence.

A new study that tested the effects of various cognitive enhancers on chess players might help clear up that mystery. Findings show that the drugs modafinil (commonly known as Provigil) and methylphenidate (frequently known as Ritalin or Concerta) can improve the performance of chess players — those studied were better after taking the drugs at performing the mental calculations needed to play chess.

However, the study also revealed some of the limitations of these effects. The enhancement caused by the drugs came at a cost to time management, especially for players who already struggled to play quickly.

Better, but slower, chess players

The researchers selected 40 above-average chess players for the study. All were men, with an average age of 37 and an average IQ of 127.7. The group had an average Elo rating — a rating system for chess skill — in the 1670s, which puts them significantly above the novice level, though not quite in the expert or master categories.

The researchers then had the players take a dose of either caffeine, modafinil, methylphenidate, or a placebo before playing a series of 15-minute matches against a computer. They played 10 games in the morning, took another dose of whatever substance they had been randomly assigned to take, and played 10 more games in the afternoon. The participants then had at least a week off before coming back to do it again. In total, the researchers used data from 3,059 chess games.

In their first analysis, they found that the players on caffeine, modafinil, or methylphenidate did about 6% to 8% better than those on placebos — enough to see a trend, but not enough to be statistically significant (to rule out the possibility, in other words, that their improved results were due to chance).

But in taking a closer look at the data, the researchers found that players who had taken the drugs spent significantly more time thinking about each move they made. This seems to have made them worse at time management, especially the players who already struggled with timed games.

But the players also seemed to have made better moves.

"This suggests that neuroenhancers ... improve the players' ability or willingness to spend more time on a decision and hence to perform more thorough calculations," the authors wrote.

The researchers then looked at the data in two other ways: They discounted games lost because time ran out, and removed the five players who struggled most with time management from the data set. These analyses significantly improved the results for modafinil and methylphenidate — the odds of winning while doping improved by 5 percentage points, enough to "bring a player from world rank 5000 to 3500 (+35 Elo points)," according to the researchers.

"In sum, these results suggest that most players will benefit from [cognitive enhancement], in particular from modafinil and methylphenidate, while those who tend to be rather slow thinkers may perform worse in time-restricted games," the authors wrote.

For people who don't play chess, the study suggests that these sorts of improvements are likely to translate to other complex tasks.

What does 'smarter' really mean?

The key to figuring out whether smart drugs — also known as nootropics — can boost brainpower is to determine exactly what sort of "smarts" are being improved. And in many ways, this recent study is one of the most informative investigations of nootropics' effects.

Several prior tests of these drugs didn't find any brain-boosting effects, but those were measuring mental deficiencies — looking at just one component of cognition and assessing when something wasn't working. Those types of tests, therefore, aren't great at measuring improvement in a way that mirrors real-life problem-solving.

"Rarely in life do we spend an entire day using a sole cognitive subdomain — attention, for example," Ruairidh Battleday and Anna-Katharine Brem, researchers at Oxford, told Business Insider in an email during a previous discussion about smart drugs. "Rather, we constantly plan, predict, and problem-solve — all of which involve marshaling subdomains of cognition and integrating their output over varying tasks and difficulties."

A test that just measures attention might highlight the instances in which someone isn't focusing, but it might not be able to measure improvement beyond a certain point.

"It is in this sense that complex tasks can approximate everyday functioning better than simple," Battleday and Brem said.

The thinking required in a chess match is, therefore, a fascinating measure of whether a cognitive boost is occurring.

To find out how effective these drugs are as cognitive enhancers more generally, however, research is still needed. According to Battleday and Brem, scientists have not spent much time analysing how these drugs boost brainpower in healthy people, even though many people use them for that purpose. But this study shows that the drugs may indeed have a powerful effect on complex thought processes.

For chess, this means that drug-testing players would most likely be a sound decision. The rest of us might need to contemplate how we feel overall about pharmaceutical cognitive enhancement.

"These substances may be able to convert fast and shallow thinkers into deeper but somewhat slower thinkers," the study's authors wrote.