“We were able to ask whether those interactions held any clues accounting for the differences we saw at age two,” said Hirsh-Pasek, who was an author of the long-term study. “It turned out we were able to account for a whole lot of the variability later on.” Quality of communication accounted for 27% of the variation in expressive language skills one year later, she said. The results were not significantly changed when the researchers controlled for the parents’ educational level.