I still don't know WHY:
The original question when I started this experiment was to understand why when I don't wash my hair, I feel "as dirty" as when I don't take a shower at all. It may seem like I've answered that question, but I haven't. I still don't actually know why. Sad face. :(
What I do know are the trends from my data. What I learned is the following:
1) A lot of it is bias and expectations and "in my head."
2) The use of water has the biggest effect on dirtiness rating, with a smaller effect from shampoo.
3) The use of leave-in conditioner has the largest effect on head smell and seemed to be the only clear and consistent correlation for head smell.
From this information I was able to make an overall conclusion that if I want to avoid feeling dirty and avoid being a smelly-head, then I should get my hair wet and use my leave-in conditioner. So, I can avoid using shampoo every day, but it seems that I do need to get my hair wet every day.
So, why do I feel dirty when I don't wash my hair? Because I didn't get my hair wet.
Yes, but WHY does getting my hair wet make me feel clean? I don't know the full mechanism. Is it that water alone is cleansing enough to avoid being dirty or is it that getting my hair wet is enough to avoid making myself feel dirty because I think I'm dirty? I still don't know.
This is a rather simple case and its rather easy to understand the difference between discovering a correlation and understanding the full mechanism. In more complicated situations it rather easy to find yourself in a grey area where you think you've discovered the "why" but you really haven't. I point this out simply to get more of you to think about what you truly understand and what you don't. You don't need to know and understand the full mechanism of everything in your life. However, if you start to recognize when you do not know the true "why" then you will start to ask "why" more often, and you could even start researching/learning some of those "whys" and then you'll have turned into a scientist.* And we sure need more scientists!
*According to The World English Dictionary on dictionary.com a scientist is "a person who studies or practices any of the sciences or who uses the scientific methods." The scientific method is really just a formalized way of asking "why." So yeah, digging into the "whys" in your life makes you a scientist. I actually rather like the way it is defined on Wikipedia too. "A scientist, in a broad sense, is one engaging in a systematic activity to acquire knowledge." Thats just lovely isn't it?
Another point I'd like to make here is that I see this as an analogy for the difference between experimental scientists and theoretical scientists. The experimental scientist just needs to know how things work. For them, "Because I didn't get my hair wet" is enough. They can use this information to create the desired outcome. They (hopefully) understand that they do not know the true why, but they don't need to acquire that knowledge. The theoretical scientist on the other hand cannot stand not knowing the full explanation. They need to find the full mechanism. They think "But WHY does water matter so much?" and it nags at them until they go figure it out.*
*This whole paragraph is purely the opinion of the TDE. This is not an official definition at ALL.
The Tap Dancing Engineer would like to thank theoretical scientists for their inability to move on from these questions. Because of this, I can get answers to some of my "whys" that I am uninterested in researching for myself. Of course, all scientists want to understand as much "why" as possible. We experimental scientists, however, just decide to move on to other questions and leave the nitpicky details to the theoretical scientists. Both are important and we support each other. And SCIENCE!
Next up, my extra trial day!
So, partially through my experiment, as I was compiling the data, I noticed the trend between leave-in conditioner and head smell. I decided to confirm this an additional way just to be sure. So, here's what I did:
Day 28: Control 1
Day 29: Body shower and dry Shampoo (so that it wasn't too visually obvious that my hair was dirtier than normal)
Day 30: Body shower only, applied leave in conditioner to dry hair
Day 31: In the morning, just before the smell rating, I sprayed a small amount of leave-in conditioner on the top of my head without my smell tester seeing this. I made sure my hair looked and felt dry just like other days and then we completed the smell test.
So, I went 2 days without shampoo or even getting my hair wet, but I applied leave-in conditioner to dry hair as a way to "mask" my head smell and test if the smell of my leave-in conditioner was the "expected" smell (given a rating of 1.)
The result? Dirty rating of 5. Man, I felt GROSS! I couldn't wait to get in the shower after the smell rating. Head smell rating was a 1. HA! SCIENCE!
So, my extra confirmation trial did in fact confirm that as long as I smell like my leave-in conditioner my head smell was rated the same as when I take a full shower. The take away here is that if I ever have to skip a shower for some reason but am worried about smelling less than fresh, I can spray on some leave in conditioner and be good to go.
Now, I know what you're thinking. Is that head smell rating even a good indication? Did you always get a rating of 1 on Control 1 days? Or, at least you SHOULD be thinking that. And the answer is that no, I didn't always get a 1 result on Control 1 days. But it's so much more interesting than you might think. Here's a list of my results for Control 1 days:
1, 1, 1, 2, 2, 1, 2
There were also multiple Control 1 days that were skipped for a variety of reasons. Sometimes we just forgot. Oops.
Anyway, what is quite interesting to me is that the first three ratings are 1. After that, the next two ratings are 2. And, these two ratings occurred while I had my period. After my period, Control 1 rating went back down to a 1. And then, well, there was a random 2 rating one day. Given that its subjective ratings on a 1-5 scale, thats pretty impressive repeatability and shows a trend related to my period. Here's a graph that illustrates it much better:
According to this data, my head smells worse (or at least different) when I have my period. Cool! Of course, more data would be better considering that the "Period Ave" is only 2 data points. However, its an interesting trend. Apparently, in some cases, a woman's menstrual cycle CAN mess everything up. Or at least make data analysis more challenging.
And with that, I think the Shampoo Experiment is fully explained. There are many opportunities for additional experimentation. Here are some suggestions:
1) Just more data in general, and of course more blind testing to help reduce bias. Even just more smellers would be a vast improvement.
2) I know what causes ME to feel dirty and MY head to smell clean, but is this the same for everyone?
3) Additional investigation of scalp scrub as my data was less than conclusive.
4) A suggestion from reader Katherine: Some trials that involve washing hair in the sink without washing body.
5) Armpit smell didn't seem to correlate to overall dirtiness feeling. Is there something that does correlate that would be a better (less-biased) way to look for trends?
6) Of course, there is the question of WHY does getting my hair wet make me feel clean?
And I'm sure there are many many more. Leave your suggestions in the comments. Take some of the suggestions and run your own experiment. Be sure to let me know what you learn!
Next week!
What will the TDE bring you next week? I don't know yet! You'll just have to wait and be surprised. Yay!
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