Counterintuitive

Counterintuitive describes ideas, conclusions, or results that run contrary to common sense or everyday experience. Even when something seems at odds with what people expect, evidence or formal reasoning can reveal that it is, in fact, correct or more nuanced than intuition suggests.

The word combines counter- (opposing) and intuitive (based on instinct or immediate understanding). It dates from the mid-20th century and is widely used in science, mathematics, economics, psychology, and journalism to flag findings that surprise lay audiences.

Examples include the Monty Hall problem, where switching doors increases winning probability from 1/3 to 2/3, despite initial intuition. The birthday paradox shows that among about 23 people, a shared birthday is more likely than not, which surprises many. Simpson's paradox describes how aggregated data can reverse trends seen within subgroups, another counterintuitive observation. The paradox of thrift suggests that higher individual saving during a downturn can reduce overall economic growth, contrary to common sense about prudent behavior.

Understanding counterintuitive results often requires rigorous analysis, statistical reasoning, or experimental evidence. The concept is related to paradoxes, cognitive biases, and anomalies that highlight limits of human intuition.