By about months of age, different circuits in the brain begin to control infants’ looking at faces, allowing infants to distinguish different faces..

2-3

Explanation:

A biological neural network or neural circuit is a set of ordered synaptic connections that occur as a result of the binding of neurons to others in their corresponding regions following neural migration. At birth, a baby has an average of 100 billion neurons, but few neural connections. These will multiply as the child grows, through environmental, sensory, cognitive and movement stimulation. Stimulating mobility and physical activity also has a positive effect on cognitive functioning by modifying the activity of certain brain areas. Physical exercise has beneficial effects on brain function, such as promoting neuroplasticity and increasing learning and memory performance, which may be due to increased expression of various neural growth factors.

Finally, environmental stimulation is basic for harmonious brain development and for laying the neurophysiological foundations of our children's future brains. Thus, there are many mechanisms that nature has at its disposal to prevent babies from being left helpless.  All of them favour their relationship with adults and thus their neurons, at a time of maximum growth of their extensions, can form the brain circuits that allow the acquisitions that make them advance in their neurodevelopment. If babies do not receive from their adults sufficient affection and attention, brain growth will be much less and their neurodevelopment will inevitably be delayed, because what makes the brain grow and change is precisely the creation of new circuits as it learns new things, and those who can learn most are the most experienced. By aboyt 2-3 months is when circuits of the brain begin to be created.