Would you notice if your soup never ran out?
Bottomless bowls: why visual cues of portion size may influence intake
People eating from secretly self-refilling soup bowls ate 73% more soup and didn’t notice.
Ig Nobel 2007
Researchers rigged soup bowls with hidden tubes so they slowly refilled from underneath. Diners with the magic bowls ate far more than those with normal bowls, but didn’t feel any fuller.
The idea: we judge how much we have eaten with our eyes, not our stomachs. (Footnote for the nerds: the lead author later had many other papers retracted, so treat his work with healthy suspicion.)
Your eyes are doing the counting, and they’re bad at it.