How we taste different colours

Link between our visual sense and our flavour perception may be stronger than you think. Does the colour of your plate affect how much you eat?

When one thinks of flavour perception, noses and taste buds primarily spring to mind. Sure, other factors such as texture, temperature and touch sensations play a part, but taste and smell are the dominant senses here, right? Well perhaps not. You only have to consider the insatiable public appetite for food porn masquerading as cookbooks to see there is meat to the old adage: we eat with our eyes.

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Charles Spence, the Oxford experimental psychologist who helped superchef Heston Blumenthal develop some of his playful multisensory signature dishes, places vision right up there with smell, in flavour's "premier league", if you will. Taste sits far below with sound and texture and touch. "Half the brain is visual in some sense," says Spence, "versus just a few per cent for overall taste senses. So in cortical real estate, vision is always going to win." This is in part why the colour of our food and drink can not only determine whether it is appetising, but its flavour, too.

The innate debate
It is often said that we have an inherent aversion to blue food because it appears so rarely in nature. But if this were true, how come the introduction of blue M&Ms (a candy similar to Cadbury's Gems) was such a roaring success? And young British consumers now happily associate the colour with raspberry flavoured drinks.

Another popular theory is that we're attracted to red food because it signals ripeness, sweetness and calories. The findings of a German study seem to back this up. Its subjects rated wine as tasting 50% sweeter if drunk under red light, rather than under blue or white. But is this an innate preference? Probably not, thinks Chris Lukehurst, head of research at the Marketing Clinic, which advises food manufacturers on product development. How colour affects appetite is inconsistent, contextual and, he says: "directly related to experience, expectations, associations, cultural norms and fashions". Think about green food and you might picture fresh, nutritious rocket, watercress or cucumber. Or perhaps under-ripe, sour fruits. However: "If I talk to you about green meat," he says, "your stomach probably turns."

It is interesting, though, that a dyed-blue steak will have the same effect, even if you know it's perfectly safe. If you get people to eat it in the dark, says Spence, "so they think it's normal, then you turn the lights up and show them the colour, some will get up and be sick straight away". Such is the powerfully aversive effect of food colour out of context.

Wine experts: easily fooled
No sommelier would deny that colour is critical in assessing a wine for age and freshness. But it has also been shown to effect how tasters perceive a wine's bouquet. It all started in 2001, when 54 enology students at the University of Bordeaux fell into the trap of using red wine terms such as chicory, coal, prune, chocolate, and tobacco to describe a white wine that had been dyed red. (They had previously tasted the same wine in its natural colour, and its aroma had evoked honey, lemon, lychee, and straw.)

Spence later did the same test on one of Spain's foremost wine tasters. "He took some time before coming to his decision," wrote Spence. "In the end, though, his struggle seemed to be about which particular red-berry fruit flavour it was that he could detect in the wine - was it raspberry or strawberry?" Tee hee. A formal study on seasoned wine tasters has since corroborated Spence's finding.

Packets have flavours, too
As well as tasting the colour of what we consume, we can also taste the shade of its wrapping. Spence has tricked people into confusing salt and vinegar crisps with cheese and onion flavour merely by switching packets. "Many of our subjects will taste the colour of the crisp packet, not the crisp itself," he says. Our brains excel in picking up associations and using them as shortcuts. When the colour makes us expect something to taste a certain way, we'll taste what we expect unless it's shockingly different.

Variety makes you greedy
Using multiple colours in sweets such as Smarties and M&Ms is a strategy to get you to eat lots of them. People will wolf down more from a mixed bowl than they will from a bowl full of their favourite colour alone. And a recent study from Cornell University showed that you'll eat more, too, if your food colour matches the plate, while a contrast will have the opposite effect.

Blind tasting
If you can't see colours, you might expect your other senses to sharpen and compensate, but blind people don't taste or smell any more than anyone else. They are, however, generally better at naming smells, which most sighted people struggle with. So they may not be tasting more intensely, but they can identify flavours better without visual cues.

Not surprisingly, losing your sight can make eating stressful, and it is thought to contribute to a diminished appetite in old age. But even losing the capacity to see colours can have adverse effects. In his book An Anthropologist on Mars, Oliver Sacks told the fascinating story of a man who experienced this after an accident. He found eating less pleasurable and started to choose black or white foods or eat with his eyes closed.