Play a Memory Game with Your Nose!

Introduction

Take a deep breath: freshly baked cookies, smoke from a wood fire, or a bouquet of roses—your nose is an amazing smell detector! Your sense of smell can not only identify a huge variety of odors, but it is also incredibly sensitive. Think about how easily you can detect if someone in your neighborhood has a barbecue just by smelling hints of smoke from a faraway grill. But how good is your nose when it comes to differentiating individual smells? Do this activity to find out!

Background

Every day you are surrounded by a vast variety of smells that your nose is able to pick up. Your sense of smell, also called olfaction, is very powerful. Everything that has an odor or smell releases specific chemicals, called odorants, into the air. These odorants eventually reach your nose and when you breathe in, they get transported deep into the space behind your nose. There, you have millions of smell receptors able to identify specific odorants. You can imagine this process like a lock-and-key mechanism where each odor molecule fits into one specific receptor inside your nose. Once the receptor binds to the chemical, it communicates with the brain by sending a signal, and your brain is able to identify the specific odor.

But what makes one smell different from another? Thousands of chemicals exist that trigger the sensation of smell, and each individual one—and combinations between them—will result in a different smell and signal pattern in your brain. Researchers now believe that we can smell up to 1 trillion (this is more than 100 times as many people as there are in the world!) different scents, meaning individual odorants as well as mixtures! Sometimes only a single chemical distinguishes a specific smell and many people, especially in the food industry, try to produce them to make artificial scents. One example is a chemical molecule called vanillin, which, as you might guess, smells like vanilla.

It is not only the individual molecule that matters—its concentration is also important. You are much more likely to smell a specific odor if there are many of the odor molecules around. If there are only a few, you probably will not even notice them. Put your nose to the test in this fun game of flavor memory!

Materials

Preparation

Procedure

Observations and Results

You probably thought this game was very easy with the first sample set. The flavors in the extracts are very concentrated. This means that in each of the solutions there are a lot of flavor molecules. When you smell these cups, all of these molecules move up into your nose and reach the smell receptors. Once the molecules bind to the receptors, your brain is able to identify the specific smell. It should not have been a problem for you to find the matching flavor pairs, as each of the flavors has its unique flavor molecule that generates a very specific signal pattern in your brain. This allows us to differentiate between flavors.

In the second sample set, it was probably more difficult to find the matching flavor pairs. This is because you diluted your flavor extract by adding one drop to 0.5 cups of water, which means that there were fewer odor molecules in each of your samples than before. There needs to be a certain amount of odorant in the air—the odor threshold concentration—before smell receptors can send enough signals to the brain to identify a specific odorant. This threshold can differ between people as well as flavors because of their different chemical properties. If you still smelled all your samples correctly in the second sample set, try to find your odor threshold for each of the flavors by diluting the samples even more!

Cleanup

More to Explore

• Your nose, from KidsHealth
• Your Nose Can Smell at Least 1 Trillion Scents, from Time Health
• Small molecules make scents, from Science in School
• Flavor Lexicon, from Flavornet
• Science Activity for All Ages!, from Science Buddies

Credits