Definition
The gap instinct is the urge to divide a continuous reality into two opposing groups — developed and developing, rich and poor, us and them — and to imagine a gap between them that is wider than the actual data shows.
Rosling treats this as the headline misperception of global development. The "developing world" picture most people carry — half the planet living in dire poverty, the other half comfortable — was roughly accurate in 1965 and is decisively wrong today. Most humans now live on incomes between the extremes, and the distribution looks like a single hump, not two camps separated by a chasm.
Why it matters
How it works
The instinct activates whenever a story presents two contrasting groups with a striking gap. Journalists reach for the extremes because they make better narratives; brains reach for them because contrasts are easier to remember than distributions. The combined effect is that almost every map of the world inside an average reader's head is a two-camp map.
Rosling's corrective is a four-level scale based on daily income — roughly $2, $8, $32, and beyond per person per day. About a billion people live on Level 1, three billion each on Levels 2 and 3, and a billion on Level 4. The middle two levels host the majority of humanity and almost none of the headlines. When a story claims a gap, the practice is to ask where the middle is and whether the cited extremes describe a few percent of cases or the bulk of them.
The gap instinct also drives the developed/developing dichotomy, the global North/South split, and many us/them framings in domestic politics. The fix is the same in each case — find the distribution, locate the majority, and re-describe the situation in terms of where most people actually are.