As we've already pointed out, babies develop fears from a very young age — including the first few months of their lives. As babies grow, their fears tend to change depending on their ability to perceive the environment around them.
In newborn babies, common baby fears include loud noises, falling, separation from parents, and strangers. At this stage, babies can't distinguish between objects accurately enough to be scared by looking at them. However, loud noises trigger the startle reflex. You might also notice this reflex — also known as the Moro reflex — when you lower your baby suddenly. It starts from birth and ends around 5-6 months. Your baby reacts this way because she feels like she has no support and is falling through the air. You can identify the startle reflex when you see the baby extending his or her limbs and arching the back before retracting them again. After a few months, you'll notice that your baby will stop giving this response and instead cry.
Towards the end of the first year, babies usually begin to appreciate the concept of object permanence. They can now understand that even if an object is not in their direct line of sight, it still exists. Babies can walk with one hand held, throw objects, say simple words like mama/dada/bye-bye, and follow one-step commands with gestures.
So, when you leave the room, your baby still has you on his or her mind and will wonder where you have gone and when you will return. He or she will fret if you don’t, increasing the fear of being abandoned. At the age of 1 year, walking away from mom may cause anxiety. If you leave your baby with a stranger, he or she will become anxious and regard them warily until you return.