The study authors enlisted help from a local Italian restaurant. Over the course of two days — serving two lunches and two dinners — the researchers randomly selected tables to receive either unusually large forks (20% larger than the restaurant’s normal fork) or unusually small forks (20% smaller than normal). They then weighed each plate of food before it went out to a customer and once again when it came back, in order to calculate how much each person had eaten.

Overall, the results showed, the customers given bigger forks ate less, leaving more on their plates at the end of each meal.

That left the study authors trying to explain why people might eat more when they’re given bigger portions, but less when they’re given bigger forks? The study authors suggest that both phenomena can be explained by the same logic.