Examined the relationship between counting knowledge and computational skills for 13 mathematically disabled (MD) first graders who showed a delay in acquiring mathematical skills and 24 nondisabled first graders. MD children's immature counting knowledge and poor skills at detecting counting errors underlay their poor computational skills on an…

Examined whether 5- and 6-year-olds understand that addition and subtraction cancel each other and whether this understanding is based on identity or quantity of addend and subtrahend. Found that children used inversion principle. Six- to eight-year-olds also used inversion and decomposition to solve a + b - (B+1) problems. Concluded that…

Validated models of mental addition processing by testing children and adults in a production task paradigm. Examined individual-difference relations between strategy choice parameters and criterion-related measures of ability. Found that individual differences in the apparently calculative processes that underlie numerical facility are highly…