Hands-on Activity A Tasty Experiment

Learning Objectives

After this activity, students should be able to:

• Explain the importance of the sense of smell to the ability of humans to recognize familiar foods.
• Explain why it is adaptive for an animal to use its senses to identify foods as being either nutritious or noxious.
• Create bar graphs comparing quantities of different items.
• Interpret bar graphs comparing quantities of different items.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

Common Core State Standards - Math

International Technology and Engineering Educators Association - Technology

State Standards

Materials List

• yogurt or pudding, 4 different flavors, 8 to 12 ounces each (use the larger amount for class sizes greater than 24); if using yogurt, choose types that are "blended" and do not contain fruitbits that might provide textural clues; it is not necessary to have all four flavors be either all yogurt or all pudding; for example, it is fine to have two different flavors of yogurt and two different flavors of pudding; see the Safety Issues section for food allergy considerations
• 4 cup or bowls, each capable of holding at least 8 ounces
• ~100 plastic spoons
• 4 watches with second hands
• 4 cardboard shoe boxes or similarly sized boxes with no lids
• 4 towels, t-shirts or fabric pieces that are just large enough to drape over the boxes
• 4 trash receptacles
• Tasty Experiment Datasheet, four per group (one for each of the four stations)

Worksheets and Attachments

Pre-Req Knowledge

• An understanding of what biological adaptation is.
• Ability to construct a bar graph (helpful, but not essential).

Introduction/Motivation

Before a scientist or researcher starts an experiment, he or she must first have a prediction about the expected outcome of the experiment. We call this prediction a hypothesis. However, a hypothesis is not simply a guess. Instead, it is a prediction based on prior knowledge of and experience with the subject.

For example, if a gardener wants to find out if it is really necessary to fertilize tomato plants, he or she might grow six tomato plants, but fertilize only three of them. In this case, the hypothesis being tested might be: Fertilized tomato plants produce more tomatoes than unfertilized tomato plants. The data collected during the experiment would either support or refute the hypothesis, such as, in this case, the total number of tomatoes produced by the fertilized plants compared to the total number produced by the unfertilized plants.

In this tomato plant experiment, the experimenting gardener collects data that involves numbers. In science, this is usually the case, because numbers can easily be compared and are based on countable things that really happened—not what the experimenter thought might happen.

In the taste experiment you will conduct next, you will taste and try to identify several different foods. You will not be allowed to see the food for any of the tastings, and for some you will not be permitted to smell the food either.

For this taste experiment, how might we collect data that involves numbers, or measuring something? (See if students have any ideas. This may be a hard question for some students, but help them to realize that they can simply keep track of the correct and incorrect responses by counting them.)

What is your hypothesis for this experiment? (Listen to student ideas. Expect them to respond with ideas such as: We will be able to correctly identify the most foods if we can smell them.)

Remember that hypotheses are not random guesses, but are based on everything you already know—your prior knowledge and experiences. Tell me what your hypotheses are based on? (Listen to student explanations. Expect them to refer to the demonstration with the student volunteer witnessed in the associated lesson demonstration, or to their own personal experiences. Then, move on to conduct the activity.)

Procedure

Experiment Preparation with the Students

1. Make sure all students know how to use the watches to determine when 15 seconds have elapsed. Explain that this is the amount of time that students are permitted before they must state the flavor of the food they just tasted—or else state that they are unable to identify it. Since students take turns being the timers, everyone must be able to determine when 15 seconds have elapsed.
2. Explain the basic procedure for the experiment, as follows:

The room is set up with four tables to serve as tasting stations, and the class is divided into four groups. Each group rotates through the four stations (and each group uses four datasheets, one at each station). At each station, two members of the group sit on one side of the table. One of these two members serves as the "feeder," because s/he feeds the food to the other students, who try to identify it. In front of the feeder is the food to be tasted; it is inside a box that is turned on its side so the rest of the team cannot see the food. One at a time, the other members of the team come to the table.The feeder puts a small amount (about one-half to three-quarters of a teaspoon) of food on a clean spoon, and gently feeds the student.

Meanwhile, the other member seated at the table is the "timer." This student tells the feeder when to put the food in the taster's mouth, and then announces when time is up 15 seconds later. Sometime during that 15 seconds the taster must identify the food, or else "give up."

Mention that that the taster must state his or her answer very quietly, so that other students who have not yet tasted that food do not hear. Also mention that the taster must identify both the type of food and its flavor. For example, if the taster thinks the food is Jello®, s/he says orange Jello®, cherry Jello®, or whatever flavor s/he thinks it is. Once the taster has given his or her response, the timer and presenter record that response on the datasheet.

3. Make sure that all students know how to fill in the datasheet, starting with identifying the tasting station number, and then listing the names of the team members that hold their noses in the left column. They enter the names of the team members that do the tasting without holding their noses into the third column, and once the taste testing begins, they enter response of each student into the appropriate "Response" column. If the taster does not give a response within the 15 seconds, the response data collected is recorded as "none."
4. Divide the entire class into four teams. If necessary, ask for help in rearranging the classroom to set up the four tasting stations.
5. At each station place one-quarter of the spoons, a trash receptacle for used spoons, a watch and a box containing a cup or bowl of food to be tasted, but cover the box with the fabric while it is in transit so that students are not able to see its contents. Also place a copy of the datasheet at each station, and a placard with a number between one and four to indicate the number of that particular tasting station.
6. Have each team choose two of its members to serve as the timer and the presenter for the first station. Have the remaining team members decide which half to hold their noses and close their eyes, and which half to only close their eyes. For teams with an odd number of students, have the extra student hold his or her nose and close his or her eyes while tasting. Be sure to explain that as they rotate through the different stations, every student will have an opportunity to do both types of tastings, and most will have an opportunity to be the presenter and/or the timer.

Class Experiment

Part 1: Conducting the taste tests

1. Once the class is clear on what is to happen, assign each team to a station and let them begin the taste tests. Watch closely to see that the instructions are being followed, and answer any procedural questions that arise.
2. When each team has finished at its first station and filled out its datasheet completely, place a new datasheet at each station and make sure the box containing the food is covered from sight. Then have the teams rotate in one direction to the next nearest tasting station. There, they choose a new presenter and timer, and divide the remainder of the team into "smelling" and "non-smelling" halves, as they did for the first station. Then they conduct the taste tests and record their data.
3. Repeat this procedure for the third and fourth tasting stations. Remind students to keep their voices as quiet as possible, and not share their food identifications with other teams as they rotate to new stations. If necessary, explain that giving away a food type or flavor would ruin the fun—and make the experiment invalid.
4. While students are conducting their tests, spend some time with each team and ask them the Investigating Questions.

Part 2: Graphing and interpreting the data

1. Once the tasting experiment has been completed, announce or write on the classroom board the foods and flavors for each of the four tasting stations. Then have each team look over its four datasheets. What do students notice about the data? Were students more successful at identifying the foods when they could smell them? If so, was there a big difference in the number of correct responses between the able-to-smell versus not-able-to-smell groups? Were the foods at some stations more difficult to identify, based on the number of incorrect responses, than the foods at other stations? If so, was this consistent across all the teams?
2. Explain to the class that bar graphs let us see at a glance the answers to these questions. Give each person a sheet of graph paper, and show the class how to set up the axes to make a bar graph of the results for the first tasting station. Make the graph consist of two pairs of vertical bars. The first pair shows the results of the able-to-smell tasters. Within that pair, the first bar shows the number of correct responses, and second shows the number of incorrect responses. The second pair of bars shows the results of the not-able-to-smell tasters. Again, the first bar shows the number of correct responses, and second shows the number of incorrect responses. Then have students choose a crayon or marker color to fill in both of the correct-responses bars, and a second color for the incorrect response bars. The use of colors means that they need to add a legend to the graph indicating what the colors represent. Ask: Why is using two different colors in the graph a good idea? Expect students to respond that colors help to make any differences in the successes of the two different tasting groups more noticeable.
3. If students have not already done so, make sure that their y-axie are labeled appropriately, such as "number of tasters," and the x-axes include labels beneath each pair of bars indicating whether they represent the able-to-smell responses or the not-able-to-smell responses. Also point out that all graphs need informative titles. Ask the class to come up with one. Examples that are fairly specific might be: "Results from Food Tasting Experiments" or "Food Taste Experiments With and Without Smell." Next, point out that the graphs need to indicate the station number and the data source. Include this information as part of the title or as a separate label elsewhere.
4. Once students have completed their graphs for the first tasting station, provide more graph paper and have them construct similar graphs for each of the other three stations. As they are working, circulate through the room and ask what they think their graphs show about people's ability to taste foods under different circumstances.
5. When teams have finished the four graphs, have each team combine the results for all four stations. In other words, ask students to determine the total number of correct responses from all the able-to-smell tastings that occurred in their teams, and the total number of correct responses from the not-able-to-smell tastings that occurred. Then have them do the same for the incorrect responses, and have them graph these results on a new sheet of data paper. Expect the bars on these graphs to be much higher than on the previous graphs.
6. By now, each student has completed five graphs. From each team, choose (or have the team choose) one graph from each of the five types. Tape them to the classroom board or mount them on a bulletin board so that results of each station are all together in one spot, and the combined results (the last graphs made) are together. At this point, any similarities and differences between the teams' results become apparent, so ask students to point these out to you. If any noticeable differences exist between teams, ask why they think these might have occurred. Finally, ask students what they conclude about whether or not smell is important to the ability to recognize and identify foods, and ask whether or not their hypotheses were supported.

Part 3: Relating the experiment to human adaptations

1. Ask students what they remember from the earlier discussion (in the associated lesson) about the adaptive value of being able to recognize and remember whether certain things are good to eat, that is, nutritious, or bad to eat, that is, noxious (harmful to one's health). Students may be interested to know that when babies are just starting to eat soft foods (after a few months of drinking only milk), they behave much the same way our early ancestors probably did when finding a strange berry or unknown root. They knew from experience that some things that looked like edible might make them sick, so they would only take a small sample at first. If they did not get sick after several hours, they would then eat a larger quantity —and of course, remember what it looked and tasted like for future reference. Similarly, infants often refuse to eat more that a bite or two of a food they have not tasted before, even though the parent knows that it is a safe and healthful food. The next time the infant is offered the food, it will eat a little more. After that, it will be willing to eat full portions. This cautious behavior when experiencing new foods seems to be instinctive (one we are born with) in humans.
2. After this brief discussion of adaptive behavior, ask the class a harder question: what is the difference between the sense of taste and the sense of smell? Give them some time to share their opinions, and then draw a map of the tongue's upper surface on the classroom board, showing the regions that respond to the sweet, salty, sour and bitter aspects of food. Then ask the class how the tongue can distinguish between different flavors of pudding, which are all sweet, if it has only the ability to distinguish between, say, sweet versus salty foods? Since it cannot, explain how the sense of smell works, especially as it relates to eating. (Refer to the Lesson Background and Concepts for Teachers section of the associated lesson.) Then ask if this information about the sense of smell is consistent with the results students obtained in the experiment. Conclusion: Food identification is difficult and sometimes impossible without the sense of smell!
3. Finally, conclude the activity and lesson by pointing out that not only is food tasting behavior adaptive, but the human body structures and senses that enable us to taste foods—which includes smells—are adaptations of the body that have helped humans survive through the years.

Assessment

Example quiz or discussion questions:

• A fellow student tells you that he is going to give you either a piece of a plain brownie or a piece of a brownie containing walnuts, but you have to close your eyes and hold your nose while you chew and swallow it. If you can correctly identify which piece he has given you, he will then give you the rest of the brownie. Do you think you will be able to correctly identify which piece he has given you? Why do you think that?
• Another student tells you that she is going to give you either a spoonful of cherry Jello® or a spoonful of orange Jello®. However, if you want more than a spoonful, you will have to close your eyes and hold your nose while you eat it and then correctly identify the flavor. Do you think you will be able to do it? Why do you think that?
• Why do some people think that food has less flavor when they have a stuffy nose from a bad cold?
• Create a bar graph similar to those students created, but showing the results of a different experiment, such as the one shown in the Effects of Studying for a Spelling Test example bar graph. Then ask the following questions:

1. What was the total number of correct answers given by students who studied for the spelling test?
2. What was the total number of incorrect answers given by students who studied for the spelling test?
3. What was the total number of correct answers given by students who did not study for the spelling test?
4. What was the total number of incorrect answers given by students who did not study for the spelling test?
5. What can you conclude from this experiment?
6. What hypothesis do you think this experiment was testing?

Investigating Questions

As students are conducting the experiment, ask the following questions:

• What do you notice about the responses so far?
• Are tasters more successful at identifying the foods when they can smell them? If so, do you see a big difference in the number of correct responses between the able-to-smell versus not-able-to-smell groups, or is it only a small difference?
• So far, does it look like your hypothesis is going to be supported?
• Do the foods at some stations seem more difficult to identify than the foods at other stations? If so, why do you think that might be?

At the end of the concluding discussion, ask:

• Why do many people complain that when they have a bad cold that food seems to lose its taste?

Safety Issues

• Well in advance of the activity, check for food allergies. Since the amount of dairy product involved in the tasting experiment is small, this is likely not a problem for students with lactose intolerances. Nevertheless, consult with parents if you have lactose-intolerant students in the class. If you must entirely avoid dairy products, use pureed fruit baby food products instead.
• Make sure all surfaces in the tasting areas are scrupulously clean before beginning.
• Have all students wash their hands thoroughly before and after serving as "feeders."

Troubleshooting Tips

Make sure that students state their food identification responses before they release their noses for the not-able-to-smell components of the tastings. If responses are given after releasing their noses, do not count them as correct responses, but instead mark them on the datasheets as "none."

Demonstrate the correct amount of food that feeders should put on a spoon: about one-half to three-quarters of a teaspoon. If they use too much, it may slide off the spoon before it reaches the taster's mouth, or the food may run out before the end of the experiment.

Remind students not to share food identification information with students who have not yet had an opportunity to taste it.

Emphasize that the point of the experiment is not to get the food answers "right," but to find out if it is harder to tell what a food is if you are unable to smell it.

Activity Extensions

Many elderly people complain that food is not as flavorful to them as it was in their younger years. Have students do some library and/or online research to try to find out if indeed this happens, and if so, why. They could also survey older people, asking them if they find food less flavorful than it was when they were younger. Also, see if you can locate a dozen or more elderly volunteers (perhaps grandparents of students) willing to visit the classroom. They can serve as the tasters for the same experiment that students performed on themselves, and students can compare results from the elderly group to their own results. This time, students would be testing the hypothesis: Elderly people will not be able to identify food as well as fourth-graders.

References

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Acknowledgements

This content was developed by the MUSIC (Math Understanding through Science Integrated with Curriculum) Program in the Pratt School of Engineering at Duke University under National Science Foundation GK-12 grant no. DGE 0338262. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.