Key concepts
Biology
Senses
Olfaction
Brain
Memory

Introduction
Did you know that approximately two million people in the U.S. 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 foods that are fresh or rotten. Even particular poisonous chemicals 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.

Background
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 in memory and emotion. As a result, our scent [memories tend[“recognition tends”?] to be strongly linked with memories. Many of the areas that receive scent information are especially old in terms of brain evolution and existed before the areas that give us consciousness[maybe “self-awareness” is better here?]. It is often difficult to consciously identify and label a smell. Instead we often 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!

Materials

  • Ten distinct, concentrated scents. These can be food extracts (such as vanilla) or essential oils (such as peppermint). One possible list of 10 includes: vanilla, almond, cherry, banana, cinnamon, lemon, coconut, orange, chocolate and mint extracts. Use single scents rather than blends.
  • Small zip-top bags (10)
  • Cotton balls (10)
  • Permanent marker
  • Several pieces of paper
  • >Pen or pencil
  • At least one volunteer
  • Timer or stopwatch


Preparation

  • Use your permanent marker to label your zip-top bags with the numbers one through 10.
  • Place a cotton ball into each bag.
  • Assign a number and bag to each extract or essential oil. Make a list of each extract or oil and which number bag it will be in on a piece of paper.
  • 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.
  • Create a chart on another piece of paper with 11 columns and three rows. Label the first column "Bag Number," and note the number for each bag here. Label the middle column "Scent, First Guess" and the third column "Scent, Second Guess."
  • On a third piece of paper, list—in no particular order—all of the scents you have chosen.


Procedure

  • Have your volunteer sit at a table with the bags spread out in front of them. Give them a writing utensil and the chart you created.
  • Tell your volunteer that they have three 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 "Scent, First Guess" in the chart you provided. How accurately do you think your volunteer will be able to identify the scents?
  • When your volunteer opens the first bag, start your timer.
  • Do not answer any questions that your volunteer asks or help them in any way as they smell each bag.
  • After three minutes have gone by, ask your volunteer to stop and close all of the bags.
  • Tell your volunteer they will get another two minutes to guess—this time with the aid of the list you created of the scents in random order. 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 "Scent, Second Guess."
  • Start your timer when they turn over the list.
  • At the end of the two minutes ask 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 five scents with no reference list, and the second five 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, mixed smells or single smells.

Observations and results
In this activity you probably found that your volunteers had a much easier time identifying the smells when they had a reference list to use. In the 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," "cookies" or "candle." When you gave them a list to use as a reference, however, your volunteer likely had a much easier time correctly identifying the scents in each bag.

Your olfactory system transmits information to brain areas of the limbic system associated with memory and emotion. 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 "holidays" because it is common to associate the smell of cinnamon with that 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 chart. Once you gave them the reference sheet, however, you provided more specific options. It was likely 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.

More to explore
Smelly Science: A Sniff Test, from Science Buddies
Battle of the Senses: Taste Versus Smell, from Science Buddies
Human Nose Can Detect 1 Trillion Odors, from Scientific American
Sniffing Out the Science of Smell, from NPR
STEM Activities for Kids, from Science Buddies

This activity brought to you in partnership with Science Buddies

Science Buddies