Piaget's substage from 12-18 months involves experimenting through trial and error. Which substage is this?

• A. Primary circular reactions
• B. Secondary circular reactions
• C. Coordination of Reactions
• D. Tertiary circular reactions

Answer: (C)

In this period infants become “little scientists,” using trial-and-error to learn about how things work. They deliberately vary how they act on objects to see different effects, not just repeat familiar actions. This curiosity-driven experimentation is the hallmark of this substage, where actions are extended and adjusted to discover new outcomes—like trying different ways to move, drop, shake, or manipulate toys to see what happens next.

Earlier substages focus more on repeating already-working actions—either with their own body (primary circular reactions) or with objects (secondary circular reactions) or on coordinating existing actions to achieve a goal (coordination of secondary circular reactions). Now the emphasis shifts to exploring new strategies and observing results, which is exactly what this 12–18-month period showcases through tertiary circular reactions.