MICROWAVE COOKING

How to 'reinvigorate' an old piece of chewing gum

Aim: to demonstrate the multisensory integration of taste and smell in the perception of food flavour

• 1 stick of mint or spearmint chewing gum
• A little icing sugar

Method:
Begin chewing the gum. Do not stop until the chewing gum has lost all of its minty flavour. Next, take the chewing gum out of your mouth and roll it in the icing sugar. Now put the gum back in your mouth and start chewing again. Did you notice any change in the strength of the minty flavor when you put the gum back in your mouth for the second time?

Result:
You should find that the minty flavour of the chewing gum miraculously returns after the chewing gum has been rolled in the sugar. By itself, the icing sugar does not have a minty taste, nor does the chewing gum after it has been chewed for long enough. The re-emergence of the minty flavour when the chewing gum is rolled in the icing sugar is due to the multisensory interaction between the sugar on your tongue and the faint smell of mint that still resides in well-chewed gum.

Your brain combines these two individually weakly effective cues in a superadditive manner in order to deliver a flavour perception that is actually far stronger than would be predicted by simply combining the two individual 'unisensory' perceptions. (In fact, this trick was used by children during the Second World War to make their gum last much longer when supplies of chewing gum were rare.)

Conclusion:
Our brains combine the cues from each of our senses in order to determine what the foods we eat taste like. One key rule used by the brain when combining different sensory cues (such as when combining tastes in the mouth and smells in the nose) is known as superadditivity. The manufacturers of commercial chewing gums typically dissolve several different kinds of sugar into their gum that each break down in the mouth at different times after you start to chew. Thus, the manufacturers are able to prolong the long-lasting minty flavour in the mouth by phasing the release of different sugar compounds on the tongue, in just the way you experienced by rolling your piece of chewing gum in the icing sugar.

For those of you who wear glasses, and who have experienced the phenomenon that you can 'hear' better when you put your glasses on, that is another example if the superadditive interaction of speech sounds and seen lip-movements.