Everyone agrees models need far more data than children. The size of the gap depends entirely on decisions about what to count, and those decisions move the answer by more than the disagreement they are meant to settle.
Why there is no single number
The comparison sounds like it should reduce to a ratio: tokens seen by a model, words heard by a child, divide. Four things prevent that.
The human figure is an estimate from small observational studies of speech in the home, extrapolated across years. Those studies vary substantially between families and between methodologies, and the best-known of them have been the subject of replication disputes.
A child’s input is not only words. It is words attached to objects, faces, actions and consequences, arriving in a causally structured stream the child partly controls. Counting only the words counts the smallest part of it.
