How to score a bigger serving of food, according to science

Rave-worthy: Researchers examined how praise affected serving size.
Rave-worthy: Researchers examined how praise affected serving size. Photo: Gelato Messina

Paying compliments pays off, at least when it comes to fast food, Austrian economists have found in a study that involved buying 100 cones of ice-cream and 800 kebab wraps.

The Innsbruck University researchers sent several people to fast food restaurants over a series of days to buy soft-serve ice-cream, the university said on Wednesday.

To measure the effect of praise and recognition in consumer interactions, the experimenters ended their order with the sentence, "You have the best ice-cream in town."

They then left the shop to weigh their serving with a small scale.

They found that the praise got them 10 per cent more ice-cream on average than when they ordered without paying a compliment.

Instead of praise, the researchers also tried tipping the salesperson at the time of ordering.

This increased the serving by an average of 17 per cent, but after accounting for the tip, the actual value increase was only 7 per cent.

Praising and tipping kebab vendors brought similar results.

Over several days, customers who paid compliments got continuously growing portions that ended up being bigger than the ones that were only accompanied by tips.

Lead author Michael Kirchler said his study showed that "there is a tendency to underestimate immaterial incentives such as recognition and praise and to overestimate monetary incentives".

To reach their findings, the experimenters did not have to gorge on fast food, but they gave most of the ice-cream to passers-by and the kebab to a charity.