Which reflex is characterized by an infant throwing their arms when startled?

The reflex characterized by an infant throwing their arms when startled is known as the Moro reflex. This reflex is a defensive response that occurs when a baby feels a sudden loss of support, or experiences a loud noise, or other surprise stimuli. When triggered, the infant will extend their arms outwards and then quickly retract them, often accompanied by crying. The Moro reflex usually appears around birth and typically disappears by the time the infant is about 4 to 6 months old.

The other reflexes listed have different characteristics and functions. The grasp reflex involves an infant's automatic grasping of objects placed in their hand, while the rooting reflex helps the baby turn their head toward a touch on the cheek, facilitating breastfeeding. The asymmetric tonic neck reflex occurs when an infant's head is turned to one side, causing the arm and leg on that side to extend, while the opposite limbs flex. Each reflex serves a unique purpose in the development of an infant’s motor skills and interactions with their environment.