Did you know that approximately 2 million people in the United States have no sense of smell? Lack of smell is a disorder known as anosmia, and can be caused by damage to the nerves that transmit information from your nose to your brain. Our sense of smell serves an important purpose, we use it to distinguish between edible and inedible items in our lives, including fresh or rotten foods, and even particular toxins that have strong, unpleasant smells. In this activity you will test the scent perception of your volunteers, and learn about how smell is closely associated with memory.
Your sense of smell is also known as olfaction. Olfaction takes place when molecules known as oderants bind to specific receptors in your nasal cavity inside your nose. When activated, these receptors transmit information along sensory nerves to the olfactory bulb, a neural structure at the base of your brain that transmits smell information from your nose to deeper brain structures. Many of these deeper structures are involved in scent processing as well as memory and emotion, and as a result, our scent memories tend to be highly associative, and strongly linked with memories. Interestingly, many of the areas that receive scent information are particularly old, in terms of brain development, and existed before the cortical areas that give us consciousness. Thus, it is often more difficult to consciously identify and label a smell, instead we associate scents with the memories and emotions that they evoke.
In this activity you will be testing scent memories in your volunteers, and learning about how we remember and recall scents!
- Almond extract
- Vanilla extract
- Mint extract
- Cherry extract
- Banana extract
- Cinnamon extract
- Lemon extract
- Root beer extract
- Coconut extract
- Orange extract
- 10 small, Ziploc bags
- 10 cotton balls
- 1 permanent marker
- Several pieces of paper
- A pen or pencil
- At least one volunteer
- A timer or stopwatch
Note: Feel free to use different extracts or essential oils if you have them available. Follow the instructions below, replacing the unused scents with those you choose to use.
- Use your permanent marker to label your Ziploc bags 1-10.
- Place a cotton ball into each bag.
- Following the order in the table below, pour a small amount of the designated extract into each bag (just enough to dampen the cotton ball). Seal the bags once the extract has been added. You can use this list as a reference, but you don’t need to copy it.
- Copy the following table on your paper:
Extract (first guess)
Extract (second guess)
- Copy the following list on another piece of paper:
- Root beer
- Have your volunteer sit at a table with the bags spread out in front of them. Give them a writing utensil and the list that you created in Preparation: Step 3.
- Tell your volunteer that they have 3 minutes to smell and attempt to identify the scents in each bag. Ask them to write down their best guess next to the bag number in the column ‘Extract (first guess)’, in the table you provided.
- When your volunteer opens the first bag, start your timer.
- Do not answer any questions that your volunteer asks, or help them in anyway way as they smell each bag.
- After 3 minutes have gone by, ask your volunteer to stop, and close all of the bags.
- Tell your volunteer they will get another 2 minutes to guess, this time with the aid of the list you created in Preparation: Step 5. Tell them that this list has all of the scents included in the activity, but not in the same order. This time they will be matching the scent to the bag with the aid of the list.
- Hand them the list facedown. Tell them that when they flip over the list, you will start your timer. This time they should write all of their guesses in the column ‘Extract (second guess)’.
- When they turn over the list, start your timer.
- At the end of the 2 minutes, as your volunteer to stop and reseal all of the bags.
- Count the number of correct answers in each column. Which task was easier for your volunteer?
Extra: Try this activity with another volunteer, but this time split the bags into two groups. Have them guess the first 5 scents with no reference list, and the second 5 scents with a list. Which one was easier for your volunteer?
Extra: Try mixing two smells together and see which are easier and more difficult for your volunteers to identify.
Observations and Results
In this activity you should have found that your volunteers had a much easier time identifying the same smells when they had a reference list to use. In this first trial, when the volunteer tried to guess the smells without knowing the possible choices, they may have written down less descriptive guesses, such as ‘candy’ or ‘cookies’ or ‘candle’. However, when you gave them a list to use as a reference, your volunteer had a much easier time correctly identifying the scents in each bag.
Your olfactory system transmits information directly or indirectly to brain areas of the limbic system associated with memory and emotion, including the amygdala, hypothalamus, olfactory cortex and hippocampus. As a result, we often have difficulty labeling scents by their name, instead we identify them by their associated memories. You might smell the scent of cinnamon and name it as ‘Christmas’ or ‘Holidays’, since it’s common to associate the scent of cinnamon with this time of year.
Because scent memories are associative, and thus somewhat difficult to label correctly, your volunteer probably had fewer correct answers in the first column of their table. However, once you gave them the reference sheet you provided more context for each of the scents they experienced. It was much easier for your volunteer to match the scent with the correct label than it was for them to identify the scents without a reference list.
Ask an Expert
- Smelly Science: A Sniff Test, from Science Buddies
- Battle of the Senses: Taste Versus Smell, from Science Buddies
- Scintillating Scents: The Science of Making Perfume, from Science Buddies
- Science Activities for All Ages!, from Science Buddies