Sensory integration refers to how people use the information provided by all the sensations coming from within the body and from the external environment. We usually think of the senses as separate channels of information, but they actually work together to give us a reliable picture of the world and our place in it. Your senses integrate to form a complete understanding of who you are, where you are, and what is happening around you. Because your brain uses information about sights, sounds, textures, smells, tastes, and movement in an organized way, you assign meaning to your sensory experiences, and you know how to respond and behave accordingly. Walking through a shopping mall, if you smell a powerful, sweet scent, you are able to identify it as a candle or essential oil and realize that you're walking past an aromatherapy store. You may linger a moment to enjoy it or hurry by to escape it.
For most of us, sensory integration occurs without conscious thought or effort. Let's say you're ironing and chatting with your child. You stay focused on your conversation and hear all the fascinating details of the latest episode of Blue's Clues. You may find that you've ironed an entire pile of shirts without even thinking. You certainly didn't have to consciously consider how to apply the correct pressure to the iron, or figure out what to do when you came across a wrinkle or finished a sleeve. You just ironed. That's how good you are at using your senses to function adaptively. Of course, if something unexpected happens, say, you notice a stain, your senses would sharpen and focus on this alerting information. Otherwise, no big deal – just another day, another pile of ironing.
For others, sensory integration happens inefficiently. People with SI dysfunction have great difficulty figuring out what is going on inside and outside their bodies, and there's no guarantee that the sensory information they're working with is accurate. In response, a child may avoid confusing or distressing sensations – or seek out more of the sensation to find out more about it. For example, a child who has difficulty integrating tactile (touch) input may avoid unpleasant touch experiences such as getting his hands messy with paint, sand, or glue, while another child may crave such touch input and actively seek it out.