word gap

In the early 1990s, a team of researchers decided to follow about 40 volunteer families — some poor, some middle class, some rich — during the first three years of their new children's lives. Every month, the researchers recorded an hour of sound from the families' homes. Later in the lab, the team listened back and painstakingly tallied up the total number of words spoken in each household.

What they found came to be known as the "word gap."