Recently I shaved off my moustache (yes, really). I’ve had a moustache all my adult life, so it felt like a big change. My face seemed very strange whenever I looked into the mirror the first few days. Yet very few people commented on it. Not even my mother noticed that I had removed my moustache, although she did straight away notice my new shoes.
This shouldn’t have surprised me. If I had been less self-centred I might have realised that:
1. The human brain is very good at recognizing faces. Once a face has been recognized, there is usually no need to analyse the details of the face (this is a simplification; at least the face may be checked regularly for changes in facial expressions).
2. It is more difficult to notice something is missing than to notice something new that is visible. The absence of moustache is less obvious than the presence of new shoes.
In our observations we are constantly working with models and assumptions. This is usually beneficial: we cannot possibly evaluate all the signals we receive. We ignore most of it and filter out what we deem relevant. The parts we filter out are partially replaced with models and assumptions: our brain knows what a face looks like, and what the room looks like. It can fill it in from memory, doesn’t need to ‘redraw’ it every second from what the eyes make out.
This works quite often, but it is not foolproof. There are many optical illusions that rely on the assumptions of our brains. You’ve probably come across some yourself.
The same mechanisms apply to other types of processing: listening and understanding, for example. How well did you really listen during that interview last week? Are you sure you attached the same meaning to each word as the person you interviewed? Just as important: did you hear what she did not say, i.e. which topics she (subconsciously) avoided?
As a business analyst I find it pays to be critical towards what is missing: which key requirements are missing, which subjects have we unconsciously skipped? Seeing those gaps is hard, though. I try to compensate with a structured approach using multiple viewpoints, and with frequent reflection on the completeness of the scope of my work. How do you compensate for your human shortcomings?