Taste and Smell

Purpose

To investigate the link between the sensations of taste and smell.

Difficulty

Procedure: Easy

Concept: Medium

Field

Biology/Physiology

Background

Read up on how we perceive taste.

There is a lot of complicated information in these websites. Focus your attention on the pathways of taste and smell leading up to the sensations. While the specific details of the receptors is not relevant, pay attention to what happens from the point the chemicals (food or odor) come in contact with the receptors to sensation in the brain. Did you notice that both taste and smell are forms of chemoreception? Understand what chemoreception is.

Are the nerves going to the brain for taste from the tongue the same as those used for olfaction (smell)? Keep this answer in mind for understanding the findings. Also investigate the difference between flavor and taste. Wikipedia is the place to start.

These sites have some very useful information:

Hypothesis

Based on your intuitive understanding of taste, do you think you will be able to taste specific foods and correctly identify them when your sense of smell is blocked?

Procedure

Obtain some common simple foods like fruits and vegetables. For example, an apple, onion, carrot, banana, etc. Be creative. On a paper write down the foods you have obtained and cut them into pieces for eating. Ask someone, possibly a parent, to randomly give you each of the foods multiple times. The more times you do this for each food, the better your results. Then close your eyes, tying a cloth around your eyes might help. Each time, without opening your eyes, eat what your partner gives you and guess what food it is. Tell your partner to mark next to each of the foods whether it is correct or not. Drink some water and rinse your mouth thoroughly. Don’t look at the results at any time.

Guess what food it is!

Ask your partner to make a new column for each of the foods. This time repeat the same with your eyes closed as well as your nose closed. Open your nose after you’ve finished guessing. Keep some tissues handy in one hand for spitting out the food if you don’t feel like eating them. If possible repeat this experiment with different people. Ask your teacher for the rules and regulations involving testing on someone else before you do this.

Results

Make a table for the percentage of correct guesses for each of the foods without the nose closed.

Make a table for the percentage of correct guesses for each of the foods with the nose closed.

The data might be better understood if a data set is created for each food such that a correct answer is 1 and a wrong answer is 0. The mean of such a data set is also the percentage of correct guesses/100.

Make two graphs, one with the nose open and one closed, for each of the foods from this data set with the standard error bars.

For each of the foods, was the difference in the accuracy of the guesses statistically significant between closing the nose and not? Perform a statistical t-test with appropriate parameters to explain this.

Discussion

What differences did you qualitatively feel between closing your nose while tasting and not closing your nose. Explain the results in the tables and graphs in terms of whether closing the nose (blocking the sensation of smell) had an effect on taste. What does the t-test say about the statistical significance of this difference in the perception of taste? Is the taste really affected or is it flavor? Explain.

Explain some plausible factors that could have influenced your results. Did you unintentionally or intentionally use other senses other than taste and smell to guess? Put this in perspective and discuss their effect on your results and conclusion.

Conclusion

What does your experiment say about the role of smell in our perception of flavor?

Extension