When a baby is born they are shocked and stressed by the events of delivery; they open their mouths in distress and take a deep breath to fill the lungs with air. As air passes through the vocal cords they produce a sound-the first cry.

Initially when a baby is born they cry to communicate-hunger, loneliness, discomfort, sadness or illness. They quickly learn that crying brings about a desired response (attention) so the response acts as a reinforcer.