Next time you’re at a bar drinking a tonic water-mixer or eating a strong citrus-based desert at home, take notice of your physical reaction to their bitter flavours. In doing so, you may just unlock a rather fascinating insight into the size of your brain.
Australian scientists have uncovered the reason why you might taste the same piece of food differently and perceived it to be more or less bitter than your friend: it’s due to the differences in the volume of your brains.
A new study, led by University of Queensland and published in Behavioural Brain Research, has confirmed that brain size and taste perception are linked.
Whether you enjoy tonic water or not, people with bigger brains typically find it less bitter.
It concluded that people with a bigger entorhinal cortex – a region in the brain located in the medial temporal lobe – perceive tonic water to taste less bitter. And so it follows: if you have a smaller entorhinal cortex, you’ll perceive tonic water as tasting very bitter.
“Everyone wants to know why we like certain foods and why individuals have preferences for bitter or sweet tastes,” says the study’s lead author, UQ Diamantina Institute Postdoctoral Research Fellow, Dr Daniel Hwang.
“It was unclear if brain size affected anything other than a person’s IQ, but now we can show it relates to how we perceive food and drink.
“Whether you enjoy tonic water or not, people with bigger brains typically find it less bitter.”
A European taste pattern
The world-first, large-scale study involved 559 participants from Australia, all who were of European descent, and 1101 Americans, the majority of whom also had a European background.
“There are variations in the brain structure between Europeans, Asians and Africans,” he says. “So the association we found is only in Europeans [as that is what we studied].”
A previous study conducted in 2016, also led by Dr Hwang, shows that around 40 per cent of the variation in quinine bitterness – with a source of bitterness being tonic water – is due to genetics. This effect is slightly higher than the impact that our genes have on the way we perceive caffeine bitterness (34 per cent).
There are variations in the brain structure between Europeans, Asians and Africans. So the association we found is only in Europeans [as that is what we studied].
It’s for this reason that Dr Hwang investigated this topic, studying one cultural group – Europeans living in the USA and Australia – to determine if there was a culturally significant association between brain size and bitter taste perceptions, supported by genetic DNA.
In order to conduct the study, researchers gave participants bitter and sweet solutions to taste, and then recorded their perceptions from weakest to strongest.
The size of their brain was later measured using an MRI scan, documenting 82 different regions. The scientists then analysed the results to identify if there was an association between perceived tastes of the solutions provided and brain volume.
“We found that the left side of the entorhinal cortex, an area of the brain responsible for memory, odour and visual perception, was larger in people who found quinine to be less bitter.
“Quinine is a key ingredient in tonic water and is commonly used to assess people’s response to a bitter taste.”
The entorhinal cortex is a section of the brain considered the hub in a widespread network for navigation and the perception of time. It is believed to make a contribution to odour and visual perception and is also the first area of the brain affected by Alzheimer’s disease in people with the degenerative condition.
Our study is a step towards understanding exactly how the brain perceives taste.
If your bitter taste perception relates to brain size, how about your IQ?
Dr Hwang explains that although one section of your brain is larger than your friends’, it doesn’t necessarily mean that your whole brain is larger.
“Most of the available studies on IQ and the size of your brain show there’s a relationship between your IQ and overall brain size – not the size of a specific region, like this study shows,” he says.
So even if you perceive tonic water to taste less bitter and have a larger left-hand-side entorhinal cortex, it’s not actually a given that your whole brain will be large, that the total volume of your brain will be quite heavy or that you have a higher IQ than your mate.
Although this study provides the first evidence that, even in healthy people, variation in brain structure is associated with taste intensity ratings, further research into this specific topic is needed to understand more about brain volume and taste perception.
“Our study is a step towards understanding exactly how the brain perceives taste.”
