The influence of shape on taste, or, what the hell Cadbury this chocolate is, like, über-sweet, how dare you

Nancy Drew Charles Spence is on the case of The Chocolate That Suddenly Became Too Sweet. In short, Cadbury changed the shape of their Dairy Milk bars, and consumers are complaining that Cadbury must have also reformulated the chocolate because now it tastes much sweeter. Spence, however, postulates that the shape of the bar might be influencing people’s perceptions of sweetness. Other studies have found that people seem to implicitly associate shapes with particular gustatory sensations – previous research has found that “sweetness has been paired with roundness in a range of different foodstuffs ranging from fruit juices to yoghurts and from milk chocolate to fruit juices. By contrast, angularity has been matched with bitterness, carbonation, and sourness in beers, sparkling waters, fruits, fruit juices, dark chocolates, salt and vinegar crisps, and so on”. If sweetness is associated with roundness, maybe making something round rather than angled will make people, at some level, experience the thing as more sweet.

However, implicit associations are a very different thing from actually changing the sensory experience. Conceptually, sure, round/sweet and sharp/bitter or whatever make sense – humans are very good at generalising lots of concepts and ideas across the senses and across all other sorts of categories. That doesn’t demonstrate any cause-and-effect – just an association. As the ancient words of wisdom go, correlation does not equal causation. I need to look more into the research of how manipulating a thing’s shape actually affects people’s sensory experience of the thing. (I’m assuming it exists; in fact, I’m reasonably sure I’ve read some of it, ages ago).

In the meantime, though, the whole Dairy Milk ~fiasco~ kind of makes me want to hunt around some newsagents/convenience stores/vending machines to see if I can find some of the old rectangular bars and do a direct taste comparison between them and the new rounded bars. Figure 1 in Spence’s paper has the old and new bar side by side – I hope someone who was around at the time cut the bars up and did some taste-testing with people (I reckon you could’ve broken each bar into its 6 pieces and done a rather underpowered randomised, within-subjects experiment on 6 people, hey?).

Actually, testing this whole thing properly wouldn’t be too hard, and doesn’t require the stomache-achingly sweet experience of eating Cadbury Dairy Milk chocolate. Get some chocolate, melt it, form it into different shapes as it cools and sets (e.g. pour some so it forms little round pools; just break off some straight-edged bits to get some angular pieces), then ask people to give you a hand. You can’t really test this yourself because you know what you’re testing and that could influence your perception – the mere knowledge that you could possibly expect the rounder shape to seem sweeter can bias your evaluation of the sweetness. So tell some friends that you just want to compare two brands of chocolate to find out which one is sweeter, and get each person to sample both chocolate shapes (making sure not to draw their attention to the shapes or to say anything about your hypothesis that shape might be important). There are a bunch of other things that would need to be considered in order for it to be a properly sound experiment – like counterbalancing the order in which the chocolate shapes are tasted (half the people should have the round one first, half should have the sharp one first, to make sure that the order in which people consume the shapes doesn’t have an effect on the evaluation), or maybe getting people to rate the sweetness of each piece on a scale rather than just saying which one is more or less sweet than the other, or making sure the two differently shaped pieces of chocolate are matched in terms of weight and temperature and other such factors – but even just as a quick and messy experiment you might be able to get an idea of whether shape might just be having an influence on the experience of sweetness.

And then you can spend hours thinking about how millions of different factors influence millions of other different factors in the context of the sensory experience of eating, because complex, multisensory experiences like that are ridiculously deep rabbit holes. Or you can just whinge that your precious Dairy Milk has been changed forever and vent your consumer outrage spleen in Cadbury’s general direction.

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