Subtractive problem solving
Like many others I learned to ride a bike through first learning how to ride a tricycle and then a bike with stabilisers before finally the bike on it's own. Recently, however, I have noticed a new approach, balance bikes. These pedal-less bikes allow children to learn the difficult skill of how to balance without extra wheels. Trikes and stabilisers are good at teaching pedalling but not great at teaching balance. Sometimes the solution to a problem is not to add something, it is to take something away.
Given that the established way of learning how to ride was so terrible at teaching balance and the solution of merely removing the pedals to create balance bikes so simple, why did it take us so long to develop and adopt this solution? There are many other similar examples, removing traffic lights and road signs from certain junctions makes them run smoother and removing priority boarding allows planes to board faster.
Leidy Klotz, an engineer at the University of Virginia, noticed that subtractive design solutions, where people remove elements were far less common that additive solutions. Reaching out to a trio of social psychologist at the university, Gabrielle Adams, Benjamin Converse, and Andrew Hales. The team academics, which I am naming the Fantastic Four, set to work studying the problem. The Fantastic Four theorised that, when faced with a problem. People default to adding more elements rather than removing them.
As we know people often use shortcuts, or “heuristics,” to help them navigate the myriad decisions they have to make in life, for example. Cars are generally faster than busses so if you need to go somewhere fast take a car over a bus. It’s not always true but it will see you right in most situations.
Heuristics are cognitively very easy and efficient. They are generally correct without taking up much effort but they are not always correct and there are some situations where they don’t work very well. Gambling on coin tosses is a good example. If you have one several tosses in a row you might conclude that your luck is in and bet higher even though the odds haven’t changed.
The conclusion of the Fantastic Four’s study is that when people are trying to change something, their habit is to ask, “What can I add?” rather than to ask, “What can I subtract or add?” They are fully capable of thinking of subtractions, they just tend to think of adding first and that often means they choose an additive solution before they even consider a subtractive one.
The default to think only of adding is our main challenge. If we can trigger the brain to think “What can I subtract or add?” subtractive problem solving suddenly becomes far more prevalent. In their study the fantastic four gave a Lego problem to several groups. The problem was always the same, stabilise this Lego tower. The tower was a solid block topped by a single block with a flat roof. Subjects would add or remove blocks but adding blocks took ten cents out of their prize money per block. The best (and cheapest) way to stabilise the tower was to remove the single block and replace the roof on the solid block. When primed with “Each piece that you add costs ten cents.” Only 41% of subjects found this solution but when primed with “Each piece that you add costs ten cents but removing pieces is free” almost two thirds found the solution. Put simply phrasing the problem in a way to open up the option of subtractive thinking encouraged it. This does not feel like a great revelation but how many times in our work and home lives to we phrase a problem in such a way that it closes off whole avenues of solutions?
For now, I am acutely aware of how I am phrasing problems. I try to ensure that all cards are not just left on the table but that the broad classes of options, additive and subtractive are drawn attention to. The findings of the Fantastic Four suggest this will markedly help and for such a simple intervention it would be mad not to open up all the possibilities.
If you want to see a good example
https://www.youtube.com/watch?v=1y32OpI2_LM&ab_channel=naturevideonaturevideoVerified
