title: The what-if of counting.
authors: Department of Psychology, University of Pennsylvania, Philadelphia 19104.
authors: E F
authors: EF
authors: Shipley
authors: B
authors: B
authors: Shepperson
mesh_terms: D001288:Attention; D002648:Child; D002675:Child, Preschool; D003210:Concept Formation; D004193:Discrimination Learning; D006801:Humans; D007804:Language Development; D008433:Mathematics; D011340:Problem Solving