www.TeachEngineering.org: Free Curriculum for K-12

Point out that the room will be set up with four tables to serve as tasting stations, and the class will be divided up into four groups. Each group will rotate through the four stations (and each group will use four datasheets, one at each station). At each station, two members of the group will sit on one side of the table. One of these two members will be the "feeder", because he or she will feed the food to the other students, who will then try to identify it. In front of the feeder will be the food to be tasted, which will be 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 will come to the table. The feeder will then put a small amount (about one-half to three-quarters of a teaspoon) of food on a clean spoon, and gently feed the student.

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

Be sure to mention 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®, he or she should say orange Jello®, cherry Jello®, or whatever flavor he or she thinks it is. Once the taster has given his or her response, the timer and presenter need to record that response on the data sheet provided.

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 directions are being followed, and answer any procedural questions that may arise.

When each team has finished at its first station and filled out its data sheet completely, place a new data sheet at each station and make sure the box containing the food is covered with the fabric. Then have the teams rotate in one direction to the next nearest tasting station. There they should 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 should conduct the taste tests and record their data.

Repeat this procedure for the third and fourth tasting stations. You will probably need to 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 need be, explain that giving away a food type or flavor would ruin the fun -- and make the experiment invalid.

While students are conducting their tests, spend some time with each team and ask them the Investigating Questions.

Once the tasting experiment has been completed, announce or write on the board the foods and flavors for each of the four tasting stations. Then have each team look over its four data sheets. 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?

Explain to the class that bar graphs will let a person 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. The graph will consist of two pairs of vertical bars. The first pair will show the results of the able-to-smell tasters. Within that pair, the first bar will show the number of correct responses, and second will show the number of incorrect responses. The second pair of bars will show the results of the not-able-to-smell tasters. Again, the first bar will show the number of correct responses, and second will show 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 will need add a legend to the graph indicating what the colors represent. Be sure to ask why using the two different colors in the graph is a good idea. Students should be able to respond that if there were differences in the successes of the two different tasting groups, the colors help make them more noticeable.

If students have not already done so, make sure that their y-axis is labeled appropriately, such as "number of tasters", and the x-axis includes 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. Good ones, ones that are fairly specific, that they might come up with are "Results From Food Tasting Experiments", or "Food Taste Experiments With and Without Smell". Next point out that their graphs need to indicate what station number the data came from. This information can be included as part of the title, or it can be a separate label elsewhere.

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 students what they think their graphs show about people's ability to taste foods under different circumstances.

When teams have finished their 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 team, and the total number of correct responses from the not-able-to-smell tastings that occurred. Then they should do the same for the incorrect responses, and have them graph these results on a new sheet of data paper. Of course, the bars on these graphs will be much higher than on the previous graphs.

By now each student should have completed five graphs. From each team, choose (or have the team choose) one graph from each of the five types. Tape them to the 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 should be apparent, so ask students to point these out to you. If there are noticeable differences 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 hypothesis was supported.

Ask students what they remember from the earlier discussion about the adaptive value of being able to recognize and remember whether certain things are good to eat, i.e., nutritious, or bad to eat, i.e., noxious. Students will also 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 primitive ancestors probably did when finding a strange berry or root. The primitive humans knew from experience that some things that looked like they might be nutritious might instead make them sick, so they would only take a small sample at first. If they didn't 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, an infant will refuse to eat more that a bite or two of a food they haven't tasted before, even though the parent knows that it is a safe and healthy food. The second time the infant is offered the food, it will eat a little more. After that, it will be willing to eat full portions. The behavior of using caution when experiencing a new food seems to an instinctive behavior (one we are born with) in humans.

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 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 can't, explain how the sense of smell works, especially as it relates to eating, as described in the Lesson Background and Concepts section. Then ask if this information about the sense of smell is consistent with the results they got in their experiment. To use a pun, does it make sense that food identification is difficult or impossible without the sense of smell?

Finally, conclude the activity and lesson by pointing out that not only is food tasting behavior adaptive, but the structures that allow us to taste foods-- which includes smell -- are adaptations of the body that have helped humans survive for thousands of years.