How Chocolate Helped Me Understand Correlations: Part 2

Here it is. The yummiest Psychology study I’ve ever read: Chocolate Consumption, Cognitive Function, and Nobel Laureates by Messerli (2012). And here’s why this study helped me get my head around correlations and what a correlation means.

When I first started my Masters programme, our first lesson was statistics. I could barely remember the statistics from my Bachelors programme let alone learning about more statistical methods, like Bayes theorem and Fourier analysis. I couldn’t get my head around why there were so many different tests, what they were all for and what they all meant. The only way for me to understand these daunting new statistics was to add some context to them. That’s when I came across this chocolate study – I finally found a study that clearly explained what a correlation means, what it doesn’t mean and how to interpret it. And that’s what I’m going to explain in this post… with chocolate.

This study wanted to see if there was a correlation between a country’s level of chocolate consumption and its population’s cognitive function (i.e. how well their brain’s are processing or functioning). But because there’s no public data on overall national cognitive function, our researcher took the total number of Nobel prize winners (Nobel laureates). You’d have to have a pretty good functioning brain to win a Nobel prize, right?

So, onto the study. Our researcher took the number of Nobel prize winners per country and correlated them against the amount of chocolate consumed per country. If you read my previous post then you will probably be able to work out what this graph means:


Did you get it?

This graph shows that there is a strong positive correlation between consuming chocolate and being a Nobel prize winner. The trend is going up, the data points are close together, and the r-value is a positive value of 0.791.

Sounds already like one more reason to eat chocolate.

What it doesn’t show is that consuming chocolate caused these people to have the brain function to win a Nobel prize. Instead, as our researcher quite rightly stated, it means that either:

  • Consuming chocolate influences the number of Nobel prize winners
  • The number of Nobel prize winners influences the amount of chocolate consumed
  • Consuming chocolate and winning a Nobel prize are both influenced by an underlying common factor

As there’s already research out there showing that chocolate consumption can improve cognitive brain function, this study can state that there’s a relationship between chocolate consumption and brain function, and suggest that eating chocolate could be what’s sprouting all these Nobel prize winners in Switzerland.

Can you see why I used this clear, concise chocolate study as a starting point to understanding correlations?! 

In reality, these findings are hypothesis-generating only and our researcher, once again quite rightly, recommended that the hypothesis be tested in a randomized trial.

Which is why I did some digging and found this review on Chocolate and the Brain: Neurobiological impact of cocoa flavanols on cognition and behavior (Sokolov et al., 2013).

If you don’t fancy reading the whole review, here’s a summary of the main points.

  • Chocolate contains a rich source of cocoa flavanols, which is believed to be the key to all these documented health benefits from eating chocolate.
  • Many of the studies also found that flavanols bring with them antioxidative effects, specifically improving blood-flow.
  • Improving blood-flow (and cardiovascular health in general) can improve brain tissue and brain function in the areas to do with learning, memory and cognition.
  • Some of the animal studies and a few human studies suggested that flavanols can protect against age-related and disease-related cognitive decline, such as dementia and stroke.
  • There are not yet enough studies to show that cocoa flavanols consistently have these benefits on the brain and body.
  • The studies that have found these benefits have shown them to be long-lasting.

Overall conclusion: Keep on testing and go and enjoy a bar of chocolate!