Sweet sounds

These yuzu chocolate mud cakes with fizzy yuzu icing may be my favourite thing I’ve baked in a long time. The texture of the cakes is ridiculous (it’s kind of like peanut butter, in that it sticks to the roof of your mouth in a delightfully and irritatingly luxurious way). And yuzu, well, I currently pay $40 for a 300ml bottle of yuzu juice (weep!) but I’ve just tracked down Australia’s only yuzu grower, who just happens to be about a 2-hour drive south from here, so if I had a car I would probably be there right now (and possibly passed out amongst the rinds of the dozens of yuzu fruit I had gorged on) but I’ll have to wait a little longer until I can beg/borrow/win a car. Then… everything I cook will have yuzu in it.


Alright, so. Enough yuzu, more science.

Eating food is a multisensory experience. (Hurr durr derp derp that’s pretty obvious.) It’s all pretty damn important when it comes to the perception of food and the enjoyment of eating: the look, the smell, the taste, the texture. But who’s the lonely sense who’s been left out of the party? It’s hearing! Poor, neglected hearing. He wants to come to the party too. He wants to consort with the other senses with reckless abandon. Why won’t you let him? Why won’t you letttt himmmm?

We might not think much about hearing’s contribution to food (beyond the pleasing crunch of crunchy things — more on that in a future post) but it turns out that the brain doesn’t exclude hearing from the party completely. In fact, our brains make implicit associations between tastes and sounds. We might not be aware of them on a conscious level (is a sweet taste high-pitched or low-pitched?) but with the right sort of task, as provided by experimental psychology, we can get a look at the furtive, illicit dalliance between hearing and taste. How thrilling.

So the task is like this. You sit at a computer with your hands on the keyboard. Words are going to flash up one after another on the screen, and they’ll either be sweet words (words like sugar, honey, maple syrup) or salty words (words like salt, crisps, pretzel). Sometimes you’ll also hear sounds played over some headphones (2 seconds of sound played on an instrument such as a violin, piano or bassoon). The sounds will either be high-pitched or low-pitched. You and some other participants start off the experiment on Condition 1, then change to Condition 2 (while other participants will start on 2 and change to 1).

Condition 1
Press the A key if: you see a sweet word or hear a high-pitched tone.
Press the L key if: you see a salty word or hear a low-pitched tone.

Condition 2
Press the A key if: you see a sweet word or hear a low-pitched tone.
Press the L key if: you see a salty word or hear a high-pitched tone.

You as a participant probably won’t notice anything amazing during the experiment. But when the researchers look at your reaction times (i.e. how fast you were at pressing the correct key after you saw a word or heard a sound) they’ll notice something very interesting. You responded significantly faster in Condition 1 than in Condition 2.

For some reason, you’re faster when a sweet word and a high-pitched tone are associated (Condition 1) than when a sweet word and a low-pitched tone are associated (Condition 2). Likewise, you’re faster when a salty word and a low-pitched tone are associated (Condition 1) than when a salty word and a high-pitched tone are associated (Condition 2). Somehow, the sweet-high and salty-low combinations just make more sense to your brain, enabling you to react and identify them more quickly — and more accurately, since participants made fewer errors in Condition 1 (although the error rates in Condition 1 and 2 weren’t significantly different statistically).

Another study using the same kind of experiment found a significant association between sour words and high-pitched sounds, and between bitter words and low-pitched sounds. However, these researchers have also tested sweet, sour, salty and bitter altogether using a different task, and the pitch associations for salty and bitter disappeared, although the associations between sour words and high-pitched sounds and between sweet words and high-pitched sounds were still there. Hmm.

And it seems like we don’t really have a good explanation for why the brain does this. There are plenty of ways of drawing parallels between properties in different senses — for example, when comparing hearing to vision, the loudness of a sound might be thought of as the equivalent of the brightness of a colour, since increased loudness and increased brightness are both experienced by us as being more “intense”. So maybe we just don’t have a good enough grasp of the properties of taste to be able to figure out something like why sweet is somehow a parallel for high-pitched. Is there a biological basis to the association? Or is it cultural somehow? Do people from different cultures experience the same associations? Would the results be any different if actual tastes were used (e.g. a bit of sugar on the tongue) instead of taste-related words?

And… and… can we influence the perception of taste by using sound? If the basis of the association is biological, maybe closely connected or overlapping brain regions are responsible for sweet tastes and high pitches. There certainly is overlap between the hearing and taste sensory pathways, not just at later stages of cortical processing but in the early stages too, as the primary taste cortex (which I discussed in my previous post) is located partly in the insula, which also plays a pretty big role in auditory processing (Bamiou et al. 2003).

So it’s a big and tenuous jump, but… can we influence the perception of taste by using sound? If the association is due to neuronal connectivity, would something taste sweeter if we played high-pitched music compared to low-pitched music? Or would something just taste wrong somehow if sound that wasn’t associated with it was played? Intriguing possibilities…

Recipe for yuzu chocolate mud cakes with fizzy yuzu icing under the cut. Recommended serving suggestion: high-pitched sounds, naturellement.

Note: If you don’t have yuzu juice, you can make a very rough approximation of it by using half lemon juice, half mandarin juice.

Yuzu chocolate mud cakes
Adapted from this Exclusively Food recipe.

300g dark chocolate (I used 80% cacao)
200g unsalted butter
125ml (1/2 cup) milk
165g (3/4 cup) caster sugar
125ml (1/2 cup) yuzu juice
2 large eggs, lightly beaten
100g (2/3 cup) self-raising flour
150g (1 cup) plain flour

Preheat oven to 160°C. Line a muffin tin with cupcake papers.

Place chocolate, butter, milk and sugar together in a saucepan over low heat and stir frequently until chocolate and butter have melted and the mixture is smooth and glossy. Remove from heat and stir in yuzu juice. Allow it to cool at room temperature for 15 minutes.

Add eggs to chocolate mixture and stir with a fork until well combined.

Stir flours together in a large bowl. Add about 1/3 of the chocolate mixture and stir it with a wooden spoon until it forms a smooth paste. Add the next third, stir thoroughly again, then the final third and stir thoroughly again.

Spoon the mixture into the cupcake papers, filling the papers about 3/4 full. Bake for 20 minutes.

Makes 18.

Fizzy yuzu icing

250g cream cheese, at room temperature
100g butter, softened
1/4 cup yuzu juice
1/2 cup icing sugar, sifted
4 tbs Texturas Fizzy

Note: Texturas Fizzy is from the Suprises line of Texturas products. I bought it at my local gourmet food store, but if you can’t get hold of it, substitute the 4 tbs of Fizzy with 1 tbs of citric acid and 1 tbs of bicarbonate of soda (Fizzy is a mixture of citric acid, sodium bicarbonate and sugar).

Beat cream cheese and butter together until smooth and well combined. Add the yuzu and beat again until smooth and well combined. Beat in the sifted icing sugar to sweeten and thicken the icing (you can use more or less depending on your tastes). Top your cupcakes with the icing.

If using Fizzy, grind it with a mortar and pestle until it is in lumps (not a powder) and fold it through the icing, then sprinkle some over the top of the icing too. If using citric acid and bicarbonate of soda, mix them together in a small bowl and then sprinkle on top of the icing immediately prior to serving. Fizzy is the preferable option for this recipe, since the Fizzy being in lumps overcomes the problem of the acid in the yuzu juice in the icing reacting with the bicarb (to produce carbon dioxide and the fizzing sensation) before it gets anywhere near anyone’s tongue. Adding the citric acid and bicarb into the icing would start this reaction immediately and it wouldn’t be fizzy by the time someone ate it, which is why it’s best to sprinkle these ingredients in a layer on top of the icing immediately before serving the cakes.

For the sweet vs salty experiment and the experiment that looked at the four tastes:
Crisinel, A. & Spence, C. (2010). A sweet sound? Food names reveal implicit associations between taste and pitch. Perception, 39, 417-425.
For the sour vs bitter experiment:
Crisinel, A. & Spence, C. (2009). Implicit association between basic tastes and pitch. Neuroscience Letters, 464, 39-42.
Bamiou et al. (2003). The insula (Island of Reil) and its role in auditory processing. Literature review. Brain Research. Brain Research Reviews, 42(2), 143-154.

  14 comments for “Sweet sounds

  1. October 10, 2010 at 12:46 pm

    Oooh, what I find really interesting here is the part about the salty/bitter tone association disappearing, because when I was reading this I felt “yes, that speaks to me” about sour and sweet seeming “high-pitched”, but I was less sure about the salty/bitter being low-pitched.

    Now, erm, Jess, if you can just tell me the *point* of this research? ;) (Yours is so much more commendable.)

    • Jess
      October 11, 2010 at 8:29 pm

      Yeah sour and sweet somehow seem high-pitched to me too, but in a way, so does salty. Bitter is definitely not high-pitched, but not really low-pitched either. I don’t know, it’s somehow so arbitrary yet somehow it makes sense… BUT ON WHAT LEVEL???

      The point of this research is wheeeeeeeeeeeeeee aren’t senses crazy?! No, it’s more along the lines of: the more we know about sensory pathways in the brain and how they interact, the more we can explain when something goes wrong. I mean, it’s not necessarily the most constructive thing in the world, but if someone had a stroke and it impaired their ability to make sense of sounds, then we found out their sense of taste was also impaired, we wouldn’t go “oh no, the damage is more extensive than we thought!”, we’d maybe just think that these pathways interact so maybe the damage is at the point where they interact and that might explain both deficits. And beyond that, maybe we can fix things when they do go wrong, although god knows how. That’s a long way off.

      I guess this study has the same underlying motivation as studies of things like synaesthesia (going to be doing a post on that verrrrry soon). People with synaesthesia aren’t suffering, per se, so it’s not being studied to try and find a cure, but it does provide insights into how the brain’s sensory processes work, and perhaps what happens when natural processes like neuronal pruning don’t go according to plan (that’s one of the hypotheses behind synaesthesia anyway).

      So it ain’t going to cure a disease any time soon, but it’s important to know, even if it seems pretty irrelevant. Or really irrelevant…

    • October 12, 2010 at 11:44 am

      Um, Jess? Can you promise me something? Can you promise that if I ever decide on a PhD topic and actually start working, rather than stuffing aroudn for another six weeks… can you please write out a justification for why what I’m doing isn’t a waste of time?


  2. October 10, 2010 at 10:44 pm

    Oh man I love Yuzu but it’s hard to get around here too. Still, that juice is expensivvve 8). Quite interesting research results as usual. Maybe I should start using my bf as a lab rat by playing noises as he eats O:).

    • Jess
      October 11, 2010 at 8:33 pm

      Yuzu is just so amazing, and I think the juice is so expensive because it’s imported from Japan, so I try not to think too much about how I’ve gone through 3 bottles of it since I discovered it in my local epicure store. O__O

  3. October 10, 2010 at 10:51 pm

    I’m not sure whether to be happy or disturbed that I know where the insula is. I am picturing it on a gross brain specimen as I type. Yum.

    This sounds almost like some kind of synesthesia that is ubiquitous rather than phenomenal. And is super interesting. What is the purpose of such connections, for example? I would want to see which parts of the brain light up when doing this. Crazy.

    I’ve never had yuzu before but you’re making me want to hop in that car with you and drive the two hours to gorge on it! These sound delicious.

    • Jess
      October 11, 2010 at 8:37 pm

      I started writing this post because I had the idea in the back of my mind to also write one eventually about synaesthesia! I think synaesthesia is just way too fascinating, and I’ve found a variation of it that is rather interesting from a taste perspective…

  4. October 11, 2010 at 11:19 am

    Oooh these look fab Jess!! I love the chocolate and Yuzu combination and the description of the cake sticking to the roof of your mouth! Now, please, PLEASE share with me where you found Australia’s only Yuzu grower? I will have to hop in my car and get down there ASAP.

    • Jess
      October 11, 2010 at 8:39 pm

      http://chillinghambushtucker.com.au :)

      Just over the border in NSW. The ridiculous thing is, it’s like a 10 minute drive along the road from the Natural Bridge, which I’ve been to time and time again because I absolutely love the rainforest around Springbrook and Binna Burra so I take any opportunity to go down that way. If only I’d known I was so close to precious yuzu!

  5. October 11, 2010 at 7:32 pm

    Sweet is definitely high pitched, it just makes sense. The word even seems a little high pitched, somehow.

    I am a big loser for not knowing anything about yuzu, but at that price I think maybe I’m happy to be blissfully ignorant?

    • Jess
      October 11, 2010 at 8:43 pm

      Yeah I have no idea how it makes sense, but it does. I’ve tried to figure it out somehow but I think we just lack the right words to describe the properties of sweetness in a way that makes it relevant to the other senses. Like maybe sweetness is kind of a “bright” sensation? So a high-pitched sound kind of seems bright? I don’t know, grasping at straws, etc., but I do wonder how many people would agree with the sweet = high-pitched association. The majority, I would imagine.

      Yuzu is beyond amazing, but maybe that’s just because I’m way too fond of citrus in general.

  6. October 20, 2010 at 12:31 am

    madly wonderful (gorgeous photos as well)!!

  7. Deborah
    March 11, 2011 at 3:03 pm

    You know of a place that grows Yuzu in Australia? Is it possible to put me in touch with them? I hope they have been spared by the recent weather. Desperately seeking yuzu- just one will do!

Leave a Reply

Your email address will not be published. Required fields are marked *