A group of 2-year-old infants are selected for a special program because their iq scores are very low. five years later, most of them have improved. one possible explanation is that the special program produced great benefits. another explanation is that

The special program that they have conducted to the infants worked. The experiment was a success. And because of this, they could conduct more, special programs and even in a larger amount of infants they can conduct this. This special program is really beneficial to each and every one of them.