Sunday, August 16, 2009

Does chocolate improve work performance?

For some time now, I’ve had a fascination with chocolate. It all started six years ago when I spotted a 10-pound bar of semi-sweet Ghirardelli chocolate on sale at Trader Joe’s in South Pasadena, California. As soon as I laid eyes on it, I knew I had to buy it. But how would I possibly consume such a large quantity of chocolate? 

Ok, it wasn't that hard - I started off making chocolate truffles, learning the ins and outs of tempering, and discovering that basically any dessert can be coated with chocolate and turned into tasty bite-sized candies which I foisted upon friends and co-workers. I went through about three 10-lb bars in this fashion.
The next step came when I organized a chocolate tasting for MIT graduate students and postdocs in 2007. As with many of my endeavors, I went a little overboard with the concept. In my quest to find all of the best chocolates to offer tasters, I read several books on chocolate, visited every shop that sold chocolate in the Boston area as well as the major online retailers, and created a 40-page guidebook detailing the chocolates for the event.

In the ensuing period since that first fateful 10-pound bar, I’ve gained a serious chocolate habit. Although I’m not someone who takes a daily coffee or tea, I started eating dark chocolate on a semi-regular basis on presumptions of “researching” new varieties. I started noticing that I felt more focused and more productive on days when I ate chocolate, and at times turned to chocolate as a mental aid when I needed to pound out some thesis work.

According to recent reports from Slate and Nature (here and here), I’m not alone in using drugs to increase my mental capacity. According to an informal poll by Nature, one in five respondents admitted to using prescription drugs such as Ritalin for mental enhancement purposes, signs of a growing trend toward “brain doping” by students, academics, and other nerds.

At present, chocolate is about as far as I’ll go to increase my research productivity, and although its effects are mild, chocolate does contain a variety of pharmacologically active substances. But was the boost in mental ability real, or was I just imagining the effect to justify my growing chocoholism? In order to find out, I conducted a semi-scientific trial last winter. It wasn’t hard to recruit volunteers (two words: free chocolate), and I ended up finding 12 people for the two-week experiment. I monitored their work habits and randomly assigned them to either eat or not eat chocolate on a daily basis for a two-week period.

Unfortunately, the results show that if anything, chocolate has a negative effect on productivity - doh! Here are the full details.


In November of 2008, I recruited 12 volunteers, mostly among MIT students and staff. The sample was composed of six women and six men, ages 21-29. I conducted a pre-experiment survey to gauge their pre-existing habits and attitudes toward chocolate and caffeine. In the survey, 2 subjects reported eating chocolate on a daily basis, 9 reported eating it at least once per week, while one reported eating it only rarely (see figure). On a scale from 1 to 5, all participants rated their enjoyment of chocolate consumption at either 4 or 5.
Each subject was assigned one of three types of chocolate: dark, bittersweet, and peanut butter cups (all purchased at Trader Joe’s). Five people were assigned to bittersweet, five to dark, and five to peanut butter cups. The different types of chocolate were meant to both validate that the observed effects were due to chocolate and to differentiate the effect of simply eating a sweet candy from the ingredients particular to cocoa. As previous studies have shown, chocolate contains many active ingredients such as caffeine and theobromine which can actively affect mood and mental concentration, and these compounds are present in higher concentrations in darker, higher-cacao-content chocolate. While the peanut butter cups contain some milk chocolate, the quantity of cocoa is much lower than that of the dark chocolates while mimicking their sugar and fat contents, so the peanut butter cup subjects essentially acted as controls.

Before the experiment began, I gave each subject a zipper bag with 5-7 servings of their assigned chocolate. Each serving contained three squares / cups, equal to approximately 1.4 ounces, the recommended serving size. In addition, they installed the software program RescueTime, which monitors the amount of time they spend working on the computer and the applications they were using. On each day they were assigned to eat chocolate, they received an email around 10am informing them to consume a serving of chocolate between 10am and 2pm. Another email was sent at the end of the day to verify that they ate the chocolate.

The subjects failed to comply during 6% of the trial days, and I drop the days in which total computer use was less than 2 hours. I use two measures of productivity: the total number of hours worked at the computer during the day, and the percentage of each day spent on work-related applications (i.e. not counting email, news sites, etc.).


In nearly all of the comparisons, the days which were treated had lower productivity than the days that weren’t, although there were not enough observations for statistical significance.

Despite this initial null / negative result, I’m still convinced there’s something to the idea that chocolate can enhance mental performance. Maybe with a more clever setup, next time I’ll come up with some the evidence. But in the meantime, I’m still conducting unscientific research on myself.

Previous research

Chocolate contains several hundred active chemicals including caffeine, theobromine, anandamide, phenylethylamine, and others. Here is the previous work I have found looking into its effects



Sweet blog...i was looking for coconut ice cream recipes. I thrifted a Donvier ice cream maker and now I am an addict! (it's a great little maker) it's great to find a local foodie! thanks amylou (in somerville)

JW said...

Hi Amylou!

If you're using recipes with coconut milk, one thing I've been experimenting with is putting a small amount (about 1 tsp) of xanthum gum in the mixture. It helps make the ice cream fluffier and softer rather than hard and icy.


Andrew said...

I think this sentence contain a mistake: "The subjects complied during 6% of the trial days" - surely compliance was much higher.