A study investigated developments in reasoning and memory as reflected by the discovery strategies of children taking part in a manipulative categorization and recall task. A total of 40 children (8 each of 18, 24, 30, 36, and 42 months of age) participated. Stimulus materials consisting of blocks, toy plates, discs, and plastic trees were presented to subjects in two phases: a presentation and a test phase. The presentation phase involved play and discovery of items tagged with stickers depicting apples. The test phase involved a direct search for tagged items. Every move a child made to check an item for a sticker was transcribed and analyzed. Children from 18 to 42 months of age located tagged items in fewer moves in the test phase than they did in the presentation phase. Older children, in contrast to younger, conducted class-consistent searches, a phenomenon suggesting the possibility of rule use. Compared with younger children, older children in the presentation phase engaged in more class-consistent searching of both tagged and untagged items; however, in the test phase older children did not handle entire groups of untagged items. This latter finding suggests that a new strategy for learning about and encoding the environment begins to appear at around 3 1/2 years of age. (RH)