TABLE 1.

Mean word exposure (range: 1–5) and CDI scores by age-half and over all infants

Age_half	M_exposure	CDI_U	CDI_Test_U	CDI_P	CDI_Test_P	Age
Older	4.52	218.93	4.20	44.27	3.00	497.53 (32.11)
Younger	4.27	96.27	4.80	6.13	0.67	401.93 (32.49)
All Ss	4.39	157.60	4.50	25.20	1.83	449.73 (58.06)

Note: Age is in days. Note that 19/87 items we tested across infants were not on the CDI (which has 396 vocabulary items), for example, giraffe.

Abbreviations: CDI, Communicative Development Inventory; P, produced; Test, tested items from study (8 per child); U, understood.