I told my aunt that she was indulging in post hoc rationalisation. She demanded an apology (and a dictionary.) But I do it too. We all do it; it’s a natural function of the human brain. We make up stories to fill in the gaps in a known set of facts. Don’t believe me? Look up from wherever you are reading this and take a very quick sweeping look at your surroundings, then come back to this. Now recall everything that you saw. Your visual cortex cannot take in every detail of every single thing caught be that sweeping glance. That’s too much information for your brain to process in a short time. Instead, it picks up salient features – shapes, colours, movements or things you expect to be there. Then, when you try to recall it, your brain fills in all the gaps, not by recalling the exact information, but by making up and interpolating. That’s how many optical illusions function: your visual cortex takes in major features then interpolates assuming continuity.
We don’t know everything – we can’t know everything, there’s too much of it – but we are very bad at admitting it. So we make things up. We fill in the gaps. This is not always helpful. Scientists have to train themselves to look for evidence, rather than making things up. On the other hand, we don’t allow politicians not to know everything, so they make things up all the time. In September 2013 there was a trial of culling badgers in a couple of English counties to reduce the spread of bovine tuberculosis. The trial wasn’t to measure the spread of bovine TB, the trial was to see whether a number of badgers could be shot consummate with reducing the spread of bovine TB. According to the objectives of the trial, not enough badgers were shot in the trial period. When he was asked about this, Owen Paterson, the Environment Secretary, responsible for the cull, indulged in post hoc rationalisation. He didn’t know why too few badgers had been shot, and his response was to make something up. What he said was “The badgers moved the goalposts.”
Now I don’t think that we are right to expect politicians to know everything. We don’t, so why should they? However, justifying policy by made-up explanations is dangerous. In that situation, the brain’s facility for filling the gaps is not useful.
Where this function of the human brain is incredibly useful is in the theatre. It lies behind the audience’s suspension of disbelief. Give the audience a hint of a location, and they will imagine the rest. Many years ago, my local community theatre group put on a production of Willie Russell’s Our Day Out. In the play, a stern, dislikeable teacher talks an errant schoolgirl down from a cliff. After the show, an audience member buttonholed the director to say how realistic the cliff had been. The cliff had actually been a small table with a piece of cardboard stuck on the front of it, plus a sound effect of seagulls. The two actors played the scene beautifully – there was real tension – and the rest was created in the audience’s imagination.
In theatre, we rely on the brain to fill in the details that the production can’t deliver. In theatre it’s art; in politics it’s courting disaster.