Fifty-one 23-to-55-month-old-infants faced two apparatuses that required the use of a rigid (box apparatus) or flexible (hose apparatus) stick-like tool to retrieve a toy stuck inside. Before attempting the extraction, however, they had to pick the only one tool (of three) on display that had the appropriate rigidity/flexibility to be effective.…

Cardinality responses are affected by both the direction and nature of the elements in the counting sequence. Error analysis suggests six stages in the acquisition of cardinality. Although there appears to be a developmental dependency between counting and cardinality, this relationship is not significant in all cases. (RH)