25 November 2014

Big Ideas on What is Normal?

One of the attractions of the monthly Bid Ideas discussions, and one of the reasons that I keep going to them, is the variety of topics that are covered. I also like the way that most of them are on something that I know something about so that I can contribute to meaningfully but they are also something that I know sufficiently little about so that I can learn something too.

Writing these blog posts is part of the learning process and is where I can restructure, reprocess and rethink my notes from the evening. These write-ups are never a historical record of the evening and they are not meant to be.

What we mean by "normal" is something that I have thought about at various times over the years, usually prompted by a news story, so I was looking forward to this discussion.

Our thought leader for the evening was Richard Barnett (on the right) who describes himself as a writer, teacher and broadcaster, mostly on the cultural history of science and medicine, and a poet. This is what he said, what others said, what I thought at the time and what I thought (much) later when I wrote this up.

The word normal derives from mathematics and most people will be familiar Normal / Gaussian distribution from school mathematics. This was derived from coin tosses and demonstrated that while a 50/50 split is expected a range of results close to this are also common and, for example, 100/0 splits are also possible these happen very rarely.

The question posed here is where to draw the line (if it can be drawn) between normal/expected results and abnormal/unexpected results.

Other distribution models exist each of which poses the question as to what a normal result is.

The mathematical normal can lead to results that need further explanation. For example, the average (mean) number of children per family is 2.4 but nobody has 2.4 children. Some of this depends on the units of measurement. If we measure people's height to the nearest centimetre then we will find thousands of people of average height but if we measure it to the nearest nanometre then we might find nobody of average height.

Normal has other linguistic usages. It can mean to mean mediocre, conformity etc. Here normal means not special when special is something good that we aspire too. In other circumstances normal is what we want to be, especially when we are comparing ourselves to abnormal people like terrorists or paedophiles.

While the definition of normal is fairly static, what counts as normal changes all the time. It used to be normal to drink and drive and, until recently, it was normal for young men to shave. Normal moves slowly and it is not usually obvious when what was normal has become unusual or abnormal.

Normal becomes even harder to define when the thing being described is not easy to measure. You can count coin tosses, heights of people, pints drunk and beards worn but what is a normal book or a normal face?

The more we talked about normal the more that I thought that normal is not a good word to use, especially when there are often better alternatives, e.g. average/mean (mathematical) or commonplace (mediocre). Similarly, it is better to say "I am not a paedophile" than to say "I have a normal sex life"; the first is clear and unambiguous but the second is loaded with context, assumptions and interpretations, all of which change over time.

It was an interesting talk on the various uses of the word "normal", and the issues around each use, which made me realise how poor a word it is and I resolved to try and curtail my own use of it. It was also another win for the certainty of Mathematics over the vagueness of Language.

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