19 ¶Because that which may be known of God is manifest in them; for God hath shewed it unto them.
20 For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse:
21 Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened.
An infant however would not be in the same category, for obvious reason.
What "category" would an infant be in, and for what reason?
Babies can clearly see what God has made, they just don't care about who made them or how the things they see got there, All they care about are themselves, they could care less about God. As they grow up they learn that the world doesn't revolve around them. Some adults never learn it though. Even most adults don't care how things God created God got there. I believe God treats them the all the same, he looks at their heart not their size, age or cuteness.