The False-Consensus Effect
You think everyone secretly agrees with you. Most of them don't.
Grounded in the research on the false consensus effect
the bias
You overrate how many people share your opinions, tastes and choices. Whatever you'd do, you assume is the normal, sensible thing, and you assume most of the room would do it too. The people who'd pick differently get filed as weird, biased, or just wrong. It's not arrogance exactly. It's that your own position feels like the obvious default, so you treat it as the baseline everyone secretly orbits. The minority always feels like the majority from the inside.
the experiment
Lee Ross, David Greene and Pamela House coined the term in 1977 in the Journal of Experimental Social Psychology. They asked Stanford students to walk campus for 30 minutes wearing a sandwich board reading 'Repent.' Then both camps guessed how everyone else would choose, and both projected their own call. Students who agreed figured most peers would agree too, around 60%. Students who refused assumed about 73% would refuse like them. Same question, two different imagined worlds.