Adding is Favoured over Subtracting in Problem Solving

Tom Meyvis Headshot

By Tom Meyvis and Heeyoung Yoon

By Tom Meyvis and Heeyoung Yoon

Consider the Lego structure depicted in Figure 1, in which a figurine is placed under a roof supported by a single pillar at one corner. How would you change this structure so that you could put a masonry brick on top of it without crushing the figurine, bearing in mind that each block added costs 10 cents? If you are like most participants in a study reported by Adams et al.1 in Nature, you would add pillars to better support the roof. But a simpler (and cheaper) solution would be to remove the existing pillar, and let the roof simply rest on the base. Across a series of similar experiments, the authors observe that people consistently consider changes that add components over those that subtract them — a tendency that has broad implications for everyday decision-making.

For example, Adams and colleagues analysed archival data and observed that, when an incoming university president requested suggestions for changes that would allow the university to better serve its students and community, only 11% of the responses involved removing an existing regulation, practice or programme. Similarly, when the authors asked study participants to make a 10 × 10 grid of green and white boxes symmetrical, participants often added green boxes to the emptier half of the grid rather than removing them from the fuller half, even when doing the latter would have been more efficient.

Adams et al. demonstrated that the reason their participants offered so few subtractive solutions is not because they didn’t recognize the value of those solutions, but because they failed to consider them. Indeed, when instructions explicitly mentioned the possibility of subtractive solutions, or when participants had more opportunity to think or practise, the likelihood of offering subtractive solutions increased. It thus seems that people are prone to apply a ‘what can we add here?’ heuristic (a default strategy to simplify and speed up decision-making). This heuristic can be overcome by exerting extra cognitive effort to consider other, less-intuitive solutions.

Read the full Nature article 

Tom Meyvis is a Professor of Marketing and Merchants’ Council Professor of Retail Management and Consumer Behavior at NYU Stern. Heeyoung Yoon is a PhD student at NYU Stern.