Leslie Rescorla followed 26 children who were late talkers at age 2 all the way to age 17. Every one of them ended up in the average range for adolescent language and reading — though they sat slightly below their same-SES peers who had not been late.
Trinity College Dublin researchers analyzed 84 toddlers playing one-on-one with each parent. Mothers and fathers produced similar quantity and complexity of speech — but used different word sets, exposing children to a partly overlapping, partly different vocabulary menu.
A French team followed 664 children from kindergarten through middle school — about 10 years — and found that a language-based bedtime routine predicted middle-school exit-exam performance. The bridge across that gap was kindergarten-age vocabulary.
A review in Current Directions in Psychological Science shows that children aren’t passive recipients of adult speech — they actively learn new words by eavesdropping. In one experiment, 4.5- to 6-year-olds learned words equally well from overhearing a phone call as from being directly taught.
An analysis of 6,163 Norwegian children found that “who is available to talk to this child” explains vocabulary development better than where they fall in the birth order — and older sisters start filling the caregiver role one to three years earlier than older brothers.