Problem solving flexibility across early development.

Cognitive flexibility allows individuals to adapt to novel situations. However, this ability appears to develop slowly over the first few years of life, mediated by task complexity and opacity. We used a physically simple novel task, previously tested with nonhuman primates, to explore the development of flexible problem solving in 2-, 3-, and 4-year-old children from a developmental and comparative perspective. The task goal was to remove barriers (straws) from a clear tube to release a ball. The location of the ball, and therefore the number of straws necessary to retrieve it, varied across two test phases (four of five straws and two of five straws, respectively). In Test Phase 1, all children retrieved the ball in Trial 1 and 83.61% used the most efficient method (removing only straws below the ball). Across Phase 1 trials, 4-year-olds were significantly more efficient than 2-year-olds, and solve latency decreased for all age groups. Test Phase 2 altered the location of the ball, allowing us to explore whether children could flexibly adopt a more efficient solution when their original (now inefficient) solution remained available. In Phase 2, significantly more 4-year-olds than 2-year-olds were efficient; the older children showed greater competency with the task and were more flexible to changing task demands than the younger children. Interestingly, no age group was as flexible in Phase 2 as previously tested nonhuman primates, potentially related to their relatively reduced task exploration in Phase 1. Therefore, this causally clear task revealed changes in cognitive flexibility across both early childhood and species.