Team:Paris Bettencourt/Citizen Science

Figure 2a: Deodorant has no effect on smell intensity. We collected samples of 300 volunteers from iGEM teams and citizen scientists. Subjects smelled 6 samples and rated their intensity.No difference was found between these 2 types of samples.The confidence interval is equal to 95%.
Figure 2b: Deodorant has a negative effect on body odor pleasantness.On the same samples, a better pleasantness has been found for people not spraying deodorant, (P=0,0235).
Figure 3a:Gender has no influence on body odor intensity.There is no measurable difference between male and female body odor intensity, (P=0,081). Figure 3b:Women don't smell better than men.No significant difference was found between male and female body odor pleasantness.

Figure 4: People aged between 20 and 35 have the strongest body odor.As expected,odor intensity was found to increase with the age. Surprisingly, teenagers are not the people with the strongest body odor. We limited our study to these four groups, to reflect the amount and age range of the participants.

Figure 5: The horror movie experiment. We collected samples of 17 volunteers before and after watching a scary movie. Differences in strength and pleasantness were not found significant overall (Wilcoxon test, difference in strength p=0.69; difference in pleasantness p=0.84) although some individuals did experience a significant change (volunteers number 3 and 9). Samples were tested by at least 4 people.The number of smell analyzes is too low to conclude anything.

Results

The Smell Game
The Smell Game was developed with a group of students from University of Rennes. This platform is used to store the smell evaluation data entered by Citizen Scientists. The Smell Game project web platform is available at: http://smellofus.synbio4all.org.
To find out more about how this project emerged and was developed see the 'The Smell Game' page on the Wiki.

Effect of deodorant on body odor
According to Fig. 2A, wearing deodorant does not alter the intensity of the smell, while people that do not use deodorant are considered to have a more pleasant smell (Fig. 2B). This statistically significant conclusion is based on more than 400 analyses of 200 unique samples.

Gender effect on body odor
There is no measurable difference between male and female body odor samples, for both intensity (Fig. 3A) and pleasantness (Fig. 3B). This result is contradictory to the popular belief that females have a less intense and a more pleasant odor (http://aurasensory.com/blog/did-you-know/fascinating-facts-about-underarm-odor-and-bacteria). One explanation could be that most women shave their armpits, which seems to be a condition that favors the bacterial growth.

Age effect on the odor intensity
Odor intensity was found to increase with the age (Fig. 4). Surprisingly, the odor intensity of the 10-20 year olds was lower than the 20-30, and 30-35 years old participants. We limited our study to these four groups, to reflect the demographics of the participants.

2. Horror movie night experiment
We collected samples of 17 donors before and after watching a scary movie. The samples were rated on a scale from 0 to 5 in strength and pleasantness. At least 4 people analyzed every sample. The difference between the after and before tube was plotted for every individual (Fig. 5). After statistical analysis, we found no global significant difference between the participant's body odor before and after watching the movie (Wilcoxon test, difference in strength p=0.69; difference in pleasantness p=0.84). Though, some individuals did experiment a significant change.

Achievements

Overall, more than 600 participants from all around the world collaborated with us (France, Poland, Colombia, Israel, UK). They were aged from 5 to 65 years old.

We hosted several smell events where Citizen Scientists were able to learn about our project and participate in it. One of the events took place at the 'Cité des Sciences' (a known Science Museum in Paris) called “Parfums Microbiens”. During three days, we held up a stand that included posters explaining the relationship between the microbiome and body odor, a place to analyze sweat samples using our 'Smell Game' software, and an area to exercise playing a 'Wii' game and donate sweat samples. During this event, we collected around a hundred samples and had about 200 people play the smell game.