False consensus effect
The false consensus effect is the tendency to overestimate how many other people share our own beliefs, preferences and behaviors. For product teams it is the trap of assuming customers think like the people who build the product.
How it works
The effect was first described in 1977 by the psychologists Lee Ross, David Greene and Pamela House, whose participants consistently assumed that most others would make the same choices they did. It arises because our own views are the most available evidence we have, and because we spend time with people like us.
In product work it shows up as features built for the team's own habits, jargon that insiders find obvious, and confident predictions about what "users" want with no research behind them. Nielsen Norman Group sums up the correction as "you are not the user": test assumptions with people outside the building.
A worked example
Before changing its rewards, a gas station chain asks the 14 people on its loyalty team, all of whom prefer points to instant discounts, to estimate how many members share that preference. Their average guess is 70 percent. A survey of 2,400 members puts it at 31 percent, or 744 people, less than half the team's estimate.
Related
Automate this in Pulse
Put to customers as a question in a Pulse survey, the team's own assumption turns from "everyone wants this" into a counted share.