Answer:
2 and the half years.
Step-by-step explanation:
So, let us fill in the gap in the question. Note that the capitalized words in the question above are the missing words in the question.
" Piaget appears to have greatly underestimated the understanding of causality in children. New evidence suggests that children as young as TWO (2) AND THE HALF years old showed causal reasoning''.
Jean Piaget was a psychologist whose main work while he was alive was mainly on the stages of cognitive development in children. Just as a reminder Jean Piaget prosed four main stages of cognitive development in Children which includes sensorimotor stage,preoperational stage, concrete operational and formal operational stage. Just like it is given in the question, During Piaget's study of cognitive development in children he underestimated the understanding of causality in children.