The question of when consciousness arises in children is a complex one and it largely depends on how you define "consciousness".
At a basic level, babies are aware of their surroundings almost immediately after birth. They can react to stimuli, such as light, sound, and touch, and they start to recognize the faces and voices of their primary caregivers within the first few months of life. They also show signs of emotional consciousness, such as happiness or distress, very early on.
A more advanced form of consciousness, known as "self-consciousness" or "self-awareness," starts to develop later. This is the ability to recognize oneself as an individual separate from the environment and others. The "mirror test" is often used as a measure of this type of consciousness. It involves placing a mark on a child's forehead and then seeing if they reach for the mark while looking in a mirror, indicating that they understand the reflection is of themselves. Most children pass this test between 18 months and 24 months of age.
Then there is the development of "theory of mind," which is the ability to understand that others have thoughts, feelings, and perspectives that are different from one's own. This usually starts to develop around age 4 or 5.
However, it's important to note that these are general milestones and there can be a lot of variation from one child to another. It's also a topic of ongoing research, and our understanding of consciousness and its development in children is still evolving.
Finally, consciousness is not an "all-or-nothing" phenomenon but more of a continuum, with different aspects and levels of consciousness developing at different times.