What is Sensory Processing Disorder?

I realized that I never gave an actual explanation of SPD, just hinted at early signs before I'd pieced them together, and then jumping straight to describing symptoms. While this might be fine for parents/readers who are already familiar with this disorder, it falls very short for everyone else! 

So, this is a separate page to provide some basic info on Sensory Processing Disorder.  To begin with, I've chosen to quote a page from the book Sensational Kids:Hope and Help for Children with Sensory Processing Disorder (SPD) by Lucy Jane Miller, Ph.D., OTR, a leading researcher in the field.  See Resources for publication information.

Dr Miller writes,

"Sensory processing is a term that refers to the way the nervous system receives sensory messages and turns them into responses.

All of us are constantly managing sensory messages.  Sight, sound, touch, taste, smell- the five familiar senses that let us hear the clock ticking in the background, feel the breeze blowing in the window, smell the cookies baking in the oven- come instantly to mind, but we're also constantly managing sensory messages from two less familiar sensory sources.  Sometimes called the "hidden" senses, the proprioceptive and vestibular senses give us our perceptions of speed, movement, pressure on our joints and muscles, and the position of our bodies.  It is your sense of vision enabling you to see the words on this page, your vestibular sense signaling that you are sitting upright while you read, and your proprioceptive sense letting you know how much resistance is needed to hold up the book.

Most of us are born with the ability to receive sensory messages and organize them effortlessly into the "right" behavioral and physical responses.  If that yummy cookie aroma coming from the kitchen turns into the smell of something burning, we don't have to stop and think about what to do.  We automatically translate the olfactory (smell) message into the behavioral response of dropping the book we were reading and rushing to the kitchen.  At the same time, the nervous system produces a physiological response- an uptick in heart rate, a rise in blood pressure, the outbreak of a fine sweat.

Sensory Processing Disorder exists when sensory signals don't get organized into appropriate responses and a child's daily routines and activities are disrupted as a result.  Let's say a boy is at play in the park when a ball careens toward his head.  If the boy doesn't connect the ball with danger and duck or raise and arm in self-defense, he could get hurt.  

If this child consistently fails to organize similar messages, chances are he will have problems in the other areas that rely on the same sensory and motor foundations.  If the problem is that he can't plan the motor action of ducking, he might also struggle with putting on his socks or making his way through crowded spaces.  If he sees the ball coming but can't judge how close it is, he may struggle with spacing letters and words.  If he sees the ball and knows it's close, but isn't alert enough to take action, it's probable that he'll miss a lot of other sensory messages important to everyday activities such as passing easily through a doorway or reaching directly for his milk glass.

As problems like these recur in multiple areas, it would be easy for this child to start feeling awkward, stupid, or just plain "different" because he can't do simple things all the other kids can do so effortlessly.  If other children begin ridiculing him, he might have trouble making and keeping friends and feeling good about himself.  His parents would become worried or frustrated.  No matter what his gifts and strengths are, life would be hard."


There are 3 distinct patterns of SPD:

Sensory Modulation Disorder- is difficulty interpreting and responding correctly to sensory information.  The body responds in a way that is unequal to the sensory information coming in.

    The child may be:

1.) Over sensitive (hypersensitive)- having an aversive or defensive reaction to sensations most people do not find irritating.  Flooded with sensory input they cannot interpret correctly, they are easily overwhelmed.

2) Under sensitive (hyposensitive)- not having enough response to sensory messages, seeming lethargic, seeming hard of hearing or insensitive to pain.  They need intense sensory stimulation in order to feel anything, and often seek it out in unacceptable ways.

3) Have mixed sensitivities- overreacting to a sensation one time and reacting normally, or under responding the next.

Sensory Discrimination Disorder- is difficulty distinguishing between the qualities of things, such as the inability to feel the difference between a baseball and a tennis ball, or the sharp and blunt sides of a knife.  

Sensory-Based Motor Disorders- either dyspraxia or a postural disorder caused by poor vestibular and proprioceptive information about body position and its relationship to gravity. 

This is the barest of overviews about SPD.  For further explanation please follow one of the links listed on the home page to go to other sites with fuller information.