The infant Moro reflex acts as a baby’s "fight or flight" reaction. It is present at birth and helps to stimulate that first big breath of life, which is often followed by crying. It is typically inhibited at approximately 4 months of post-natal life and is replaced by the adult “startle” reflex. The mature startle reflex is characterized by a startle response to a loud sound or sudden sensory input from the environment. The individual will then scan the area to locate the source of danger, if no danger is present, the child will ignore the stimulus and return to what they were doing.  

When the Moro reflex is not integrated at 4 months, it continues to trigger in response to a stimulus in the environment, setting off an instantaneous "fight or flight" body reaction. This happens regardless if the environment is safe. This happens before the conscious part of the brain has time to assess the safety of the situation. Children who have an ongoing Moro reflex tend to be over-reactive to what seem to be minor triggers in their environments. They often have difficulty filtering unwanted sensory input in their surroundings resulting in “sensory overload”. This can have a negative impact on their social interactions, attention and behaviour.