Preliminary research suggests that SPD is often inherited. If so, the causes of SPD are coded into the child's genetic material. Prenatal and birth complications have also been implicated, and environmental factors may be involve. In the end, causes are likely to be both genetic and environmental. SPD may impact only one or multiple sensory systems. It may impact just touch, just sight, or just movement—or more than one sense. One child may over-respond to sensation and find clothing, physical contact, light, sound, food, or other sensory input to be unbearable. Another might under-respond and show little or no reaction to stimulation, even pain or extreme hot and cold. Some have impaired sensory processing of messages from the muscles and joints so their posture and motor skills can be affected. Still others exhibit a craving for sensation that is in perpetual overdrive. If environmental sounds are irritating, try giving the child comfortable earplugs to wear to help dampen the decibel level, while still allowing them to hear speech sounds and other important sounds. Avoid using florescent lights as the hum can bother theses children and the flickering lights can even make objects in the environment appear to be moving.