The right answer is thinking.
The "thinking" is not a reflex, it is a competence that the newborn will acquire a few months after his birth.Studies have shown that babies begin to think 4 months already, they have an idea about the laws of physics. He continues to reconstruct the image he makes of the world according to the latest information he receives.
At 8 months, his brain already models the probability of future action by confronting his memory with the information his senses provide. One of the keys to human intelligence.