FRIDAY, Dec. 10 (HealthDay News) -- Toddlers who play with different-shaped objects learn new words twice as fast as those who play with objects that have similar shapes, a new study finds.

University of Iowa researchers worked with 16 children who were 18 months old and knew about 17 object names at the start of the study. Some children were taught the names of objects by playing with toys that were nearly identical, while others played with toys that were significantly different.

One month after this training, the children who played with diverse objects were learning an average of nearly 10 new words per week, compared with four words for the other children. Learning four words per week is typical for children that age who haven't received any special training.

Further research is needed to pinpoint why the children who played with diverse objects learned new words more quickly, said the researchers.

The study appears in the December issue of Psychological Science.

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The American Speech-Language-Hearing Association offers activities to encourage speech and language development.