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Illusions Exhibition

Taste Test

Sensory illusions with the taste buds. How expectations change impressions.

The things you’ll need

• Food colourings
• Water
• Rice/Potatoes/Noodles

The preparation

Make some coloured food before class by cooking pasta, rice or potatoes in coloured water. Check on whether any students have relevant food allergies.

The activity

Explain to your students that you have added something in the cooking of one batch of a type of food, but not in the other, but do not show them the food. Divide the students into two groups. Blindfold one group. Ask both groups of students to taste test both a normal and a coloured batch of the same foods. Compile and compare the results. Typically, the blindfolded group will not report any difference in taste but the group who saw the colour of what they were eating will imagine tastes which were not there.

The inside story

The senses of sight and taste are technically unrelated but they can have a strong psychological influence on each other. There are thousands of taste buds on your tongue, most being found on or between bumps called papillae which cover the tongue surface (you can just see these papillae with the naked eye). ‘Taste buds’ are actually chemo–receptor cells which each have a pit of a very specific shape. When a substance with the matching chemical shape comes along, the receptor cell sends a signal to the brain.

The follow-up

• Why was it important to have one group of people who could see the food and another group of people who couldn’t ?
• When margarine is made it is actually a translucent white colour. Colourings are added to this and many other foods so that we perceive them as tasting better, even when the taste hasn’t changed at all. What do your students think about this? Would they buy uncoloured versions?

The options

For novelty value, you could prepare other coloured food. Bake a batch of blue biscuits for example, or a loaf of red bread. Alternatively, you can involve your students in the preparation and then your students could do this experiment with other students, parents or teachers as the subjects. You could ask your students to collect example products or to survey the food they have at home to see which ones have colourings. Conduct taste tests comparing name brand food and drinks with no-name versions.

Hints

The secret here is to make sure the non-blindfolded group doesn’t give clues to the blindfolded group!