Manufacturers and marketers have long stuck by three certain "dimensions" of food - taste, texture and smell.

But what if there was a fourth?

Researchers are exploring the intriguing possibility of such a factor - colour - which interacts with the other three, and applies not just to the food itself, but to the way it's advertised.

"People will talk about the taste, smell and flavour of food, but it's only if something looks unusual that they'll mention the colour," said Dr Gavin Northey, a marketing lecturer at the University of Auckland's Business School.

Evidence from his and others' research, strongly suggests that colour primes us to experience the other elements of flavour in certain ways.


For example, people fed spoonfuls of red and blue custard with identical texture will rate the red custard as creamier and the blue custard as crunchier, or less creamy.

And people asked to smell white wine with red colouring tend to rate it as if it were a red wine - even some professional wine tasters are caught out.

Northey and his fellow researchers wondered if colour influenced not only how we experience or perceive food, but what we expect it to taste, smell and feel like even before putting it in our mouths.

So, they designed an ingenious series of studies to investigate colour's "cross-modal" effect on the expected texture of food.

In the first study, participants were shown three ads with an image of mocked-up foods - a creamy-looking salad, a crunchy-looking biscuit, and a "neutral textured" quiche-like food, neither particularly creamy nor crunchy.

Half saw the ads with a red filter over them, half with a blue filter.

Those who saw the blue filter were more likely to expect crunchiness in all foods.

In the second study, text indicating either creaminess or crunchiness was added to the red and blue ads.

When people saw ads with "crunchy" labels, the cross-modal effect of colour on expected texture was evident.

When ads with "creamy" labels were shown, the labels inhibited the cross-modal effect of colour.

"It seems that the concept of creaminess and the consumption of creamy foods is such a powerful, hedonic personal experience that it can interrupt automatic sensory-level perception," Northey said.

The third study teased out this interaction between a food ad's wording and colour.

It repeated the second study but added a measure of sensory sensitivity, called the "Need For Touch" (NFT) scale.

People with high NFT, as the name suggests, feel compelled to touch objects - they pick up and handle fruit at the grocers, for example.

As the researchers predicted, colour influenced expected texture differently according to people's "need for touch".

Depending on a person's predisposition for touching objects (their NFT), they responded to colour cues very differently.

High NFTs saw foods in red ads as being creamier than foods in blue ads; by contrast, low NFTs perceive red foods as being less creamy.

"We had thought that those who have low sensory sensitivity, as measured by need for touch, would attend to the ad copy and discount the colour - given that language often overrides the innate influence of colour on food texture," Northey said.

"But, these results suggest people at each end of the sensory spectrum, rather than being more or less sensitive to sensory stimuli, actually experience very different things.

"This is really interesting, as other studies have shown that about a quarter of the population have low sensory sensitivity."

The fourth study found that expected creaminess - but not crunchiness - strongly influences expectations of pleasure, quality, likeability, and intent to purchase in people with low sensory sensitivity.

This was in line with previous research Northey conducted with a team from Australia, which found creaminess was central to evaluations of pleasure and purchase intent following consumption.

Evidence of crossing-over between the senses has led researchers to rethink the phenomenon known as synaesthesia, where a stimulus in one sensory mode causes an experience in another mode - for example, on hearing a musical note they see a certain colour, or on hearing a word they experience a taste.

"It was once thought that only one in 25,000 people have synaesthesia, but over the last decade that estimate has been revised to one in 20," Northey said.

"Brain scan studies have revealed neural pathways that enable different senses to 'talk' to each other.

"The thinking now is that synaesthesia actually lies on a spectrum.

"Rather than synaesthetes being the only ones to have a special, direct pathway between the senses, they have a heightened experience of pathways common to us all."

In future studies, he hoped to untangle the influence of colour on expected smell and taste - and how that interacted with people's sensory sensitivity, and check whether the colour of food packaging has similar effects to the colour of ads.

The upshot for advertisers from the expected texture studies: "Know the textural cues of colour, and make sure the palette and words you use both line up with the texture you're trying to convey."