By what age should a baby typically be able to startle to loud noises?

A baby typically demonstrates the ability to startle in response to loud noises around 8 weeks of age. This reflex is part of the startle reflex, also known as the Moro reflex, which is an important developmental milestone in infancy. It indicates that a baby's auditory system is functioning and that they are beginning to respond to external stimuli, which is crucial for their sensory development.

At around 8 weeks, infants are more alert and engaged with their environment, allowing them to react more noticeably to sounds. While some newborns may respond to loud noises in the first few weeks, the consistent and pronounced startle response emerges as their neurological development advances, typically stabilizing by 2 months.

Milestones prior to 8 weeks are usually more focused on basic reflexes and initial responses, but the startle reaction becomes more defined as babies grow. Each milestone contributes to the overall development of the child's sensory and cognitive abilities, laying the groundwork for future auditory and social interactions.