The amount of time parents spend talking about numbers matters more than was previously known. Children whose parents talked more about numbers were much more likely to understand the cardinal number principle (that the size of a set of objects is determined by the last number reached when counting the set.
Susan C. Levine, Linda Whealton Suriyakham, Meredith L. Rowe, Janellen Huttenlocher, Elizabeth A. Gunderson. What counts in the development of young children’s number knowledge? Developmental Psychology, 2010; 46 (5): 1309 DOI: 10.1037/a0019671
Keep counting, parents!