#T03 Beware the “either or” of binary thinking

a baby learning
a baby is learning about her world

Learning to understand the world

From our earliest days, we try to make sense of the world by dividing it up into categories:

me/not me, safe/not safe/, dog/mum

and so on.

These are called “binary” categories, because everything has to fit into one of the two choices.

“Would you like tea or coffee?” forces you to choose one of the categories.

You might prefer milk, but you can’t have it, because it is not available to you.

Binary categories are how we navigate people and things in the real world.

We use categories like:

like/dislike, good/bad,  hungry/not hungry, day/night, presence/absence, ill/well.

Binary thinking is quick and easy.

To survive we need to think quickly and easily about our world. However, binary thinking also oversimplifies the world.

Unless we live on the equator, day/night are not discrete binary categories. Twilight blends day into night; sunrise gradually turns night into day.

The same is true of many other supposedly binary categories.

Type two diabetes can show a range of symptoms, from mild to severe.

So can depression and  conditions like autism, dyslexia and bipolar disorder.

Thinking about spectrums

We are learning to talk about these conditions in terms of spectrums. The analogy comes from the light spectrum:

there is a continuum of wavelengths of light, each associated with a particular colour

The wavelength of light increases continuously from left to right from about 380 to 780 nm.

The colour changes imperceptibly depending on the wavelength.

We can use the spectrum to distinguish obvious landmarks such as red or blue.

Recognising the exact shade of red or blue is much more difficult.

Traditionally, genetics has been built on binary thinking.

Its founding father Gregor Mendel studied differences in pairs of contrasting characters.  Such as tall/short pea plants or round/wrinkled pea seeds.

It is easy to think that everything is like that.

In fact, everything is not like that.

In a population of individuals, most characteristics vary continuously from the minimum to the maximum.

Think of human height,  it is more like a spectrum than a binary category. Individuals can be any height, rather than just being either tall or short.

#T03 We need to be very wary the “either/or” of binary thinking. 

One of the biggest pitfalls of binary thinking,  is the binary category of nature/nuture. This is causing real problems in our contemporary thinking on genetics.

Of this, much more, later.

#T02 Genes are generalists

The Jim twins
The Jim twins – identical, but separated at birth.

The fascination of twins

The 1980s were the golden age for twin studies. Identical twins share the same DNA, because they come from the same single fertilised egg.

Some pairs of twins were (sadly) separated at birth to be adopted into different families. Many did not know they were twins until they were adults.

Separated identical twins are a natural laboratory for studying the effects of genes and the environment on behaviour.

Thomas Bouchard studied such twins in the University of Minnesota. One pair, both called Jim, became international celebrities.

The Jims were remarkably similar, enjoying maths and carpentry at school, but not spelling. They both married  women named Linda and then Betty.

The Jims both had a child called James Allan.

They both worked in the security business, both drove a Chevrolet, and both chain smoked the same cigarettes. Their families took holidays on the same beach in Daytona at the same time of year.

The conclusion drawn was that their genes were somehow producing these behaviours and that there had to be many genes to produce such specific effects.

How many genes are there?

I remember being in seminars where these (and other similar) findings were being shared. This was “cutting-edge” science and we were caught up in the enthusiasm. One (now very) eminent geneticist speculated that there had to be at least 250 000 human genes.

The idea was that one (or more) genes somehow caused each of these characteristics. Jim and Jim were machines built by their genes.

We no longer think like that. The Human Genome Project reported that there were 30 000 genes; now we think it is nearer 20 000. There are fewer genes than there are human proteins, so the old idea that one gene produces one protein is also wrong.

Furthermore, the idea that there are genes “for” choosing a type of car or a wife by her name or a beach to holiday on is also redundant.

Genes shape personality but only in very general ways, probably through their effects on brain development and the actions of  nervous systems.

So, the second tool for clear thinking is:

#T02 “Genes are generalists: they only have an indirect effect on the development of characteristics.”