Drinking water and teaching science

Someone caught me at lunch yesterday and said I'm the one she wanted to talk to. She had heard a study or report about drinking water and wondered what I thought. I told her I hadn't heard anything recently, but that I knew the standard recommendation, 8 glasses of water a day, was not based on careful science. It was a back of the envelope rough calculation from several decades ago. It was for total water, including water content of food, so the actual number of glasses required was smaller. The basic rule is drink when you are thirsty.

She said the amount of water being less important but that water itself was important. She was clearly indignant that they should suggest drinking water isn't as much as it was cracked up to be. I noticed she had three glasses of water on her tray. Then she made the kind of statement I frequently hear but cannot quite understand. She asserted "I disagree with it". The way she stated it was clear that she just didn't like it emotionally. She felt water was good and was offended that they were suggesting we didn't need quite as much. She had no reasons. She hadn't looked at the data. She wasn't aware of a weakness in the study. She didn't seem to have any interest in weighing the evidence to find out if maybe she was wrong. She just disagreed. I think it was almost a moral disagreement.

I don't know why people would have an emotional attachment to drinking a lot of water. I suppose it makes them feel they are cleaning their system. Of course, they can drink all they want. When the science supported her preference, she was happy, but she was indignant that maybe it was wrong. To me, it makes more sense just to see what the evidence suggests, and adjust accordingly. The same view is often expressed by students and others. "I disagree" with this result or that, because it doesn't feel right emotionally, without even thinking they need to look at the actual study. It happened in class this week when we discussed the role of genes and evolution in human behavior. Many confidently asserted their view on what affects our behavior without feeling the need to weigh evidence or look at the studies that have been done. I tried to point out that although studies with humans are difficult, it is possible to test these views, not just assert them.

I remember as I progressed in my scientific training I found myself more and more likely to question when people would make such an assertion. I would ask what evidence they had. This doesn't make you too popular, and I try not to do it too much in casual conversation, but it is a habit of mind in science. It's a habit that should be more common. More than any actual knowledge, it is habits of mind like these that is most important in a science education.