A team of scientists from the United States and Israel exposed 24 infants to a videotaped puppet show. They used the puppets for addition and subtraction while observing the reaction of the babies. For example, they started the show with two dolls. Before the show ended, a doll was removed and then the infant’s vision was blocked with a screen. When the screen was taken away, either one doll was left, as expected, or two dolls, which would not be mathematically correct. The infants looked at the screen longer (8.04 seconds) when the number of dolls was two, which did not agree with the solution of 2 – 1 = 1. On average, they gazed at the screen for 6.94 seconds when the correct number of dolls was on the screen.