I reckon you should always be on a lookout for your child's unique spark of intelligence at any age. Be observant and see if a child had paid special focus on a particular skill set and hone on that talent to develop it further. For example, my mom noticed that I started to be interested in books at a young age (2) and she started to teach me how to read. Then she started teaching me to spell and write by the time I turned 3.
Kids can show their intelligence when they started to play with toys their way just observation can grab it easy