See the difference:
Average word counts heard by children per day - and correlated with IQ at age 3,
based on study by Drs. Hart and Risley (1995).
LENA Research Foundation
Get Accurate Information on Your Child’s Language Development with LENA.
How much talk and conversation is needed to ensure your baby’s optimal growth?
30 million words.
Researchers Betty Hart, Ph.D., and Todd R. Risley, Ph.D., conducted nearly 10 years
of research to learn why some children perform better than others in school; they
published their findings in the book Meaningful Differences. According to the book,
the answer is words. The quantity of talk and interactions that parents had with
their child, explained Hart and Risley, predicted a child’s IQ and vocabulary size
more so than any other variable, including parents’ education or socioeconomic status.
After the first four years, however, it is virtually impossible to close the gap
between children whose parents have provided this advantage and children of parents
who have not.
* Because of differences in measurement technique, 30,000 words in the Hart and Risley
study is equivalent to about 21,000 words in the LENA Adult Words report. Hart and
Risley recorded one hour at a peak talking time and extrapolated this number of
words to a 14-hour day. LENA percentiles and word counts are based on 12 consecutive
hours of recording during an actual day, with no extrapolation.