In addition to the five best known senses – taste, touch, hearing, sight and smell, there are also two others that play an important role in a child’s development – the proprioception and vestibular systems.
TOUCH (TACTILE SYSTEM)
The tactile system refers to the awareness of touch through receptors in the skin. It consists of two levels – discrimination to tell us where the touch is on our body, and a second level to tell us whether it is a safe or dangerous touch (sometimes known as a ‘fight or flight’ response). When a child is having difficulty in processing touch sensation, their brain may misinterpret the information, and label sensations as dangerous unnecessarily, causing them to overreact to light touch. Deep pressure touch is calming to the sensory system – this is why a massage is so relaxing!
SIGHT (VISUAL SYSTEM)
The visual system interprets what we see. It is necessary to recognizing shapes, colours, letters, words, and numbers. It is also important in reading body language and other nonverbal cues during social interactions. Vision guides our movements, and we continually check out actions with our eyes to make sure we move about safely. When children are having difficulty with visual processing, they may have difficultly filtering out the unnecessary details, or may have trouble identifying important information.
HEARING (AUDITORY SYSTEM)
We use our auditory system to identify the quality, and direction of sound. It not only hears sound, it also helps us to understand speech. When a child is having problems with auditory processing, they have difficulty with identifying the important information, and blocking out the background noises. They may be very sensitive to loud noises, or easily distracted by small noises (like the sound of the ceiling fan). Children with auditory processing difficulties will often struggle to focus in busy environments, and may need to be told instructions over and over.
TASTE AND SMELL (GUSTATORY AND OLFACTORY SYSTEM)
Taste and smell are senses very closely linked and work as one integrated system. The sense of smell is one of the oldest and most vital parts of the brain. The two senses together allow us to identify foods that we enjoy, and also tell us what is safe to eat. If a child’s sense of smell or taste is not working properly, they may identify foods as unsafe or dangerous, and refuse to eat. Smell is also directly linked to our emotional brain – we can use smells to access feeling of calm, alertness or pleasure within the brain.
MOVEMENT (VESTIBULAR SYSTEM)
The vestibular system contributes to our balance and our sense of where our body is in space. It provides the most input about movement in the body, and works with the auditory and visual system to give accurate information to the brain about the direction the body is moving. It is important for the development of balance, coordination, eye control, attention, and even some aspects of language development. If a child is not processing vestibular information effectivTely, they will have difficulty with balance and coordination, and will rely on visual information to give them feedback about their body. Movement input received by the vestibular system is generally alerting and can impact the nervous system for 6-8 hours.
BODY AWARENESS (PROPRIOCEPTION SYSTEM)
Proprioception or Kinesthetic System refers to the perception of sensation of the muscles and joints enabling the brain to know where each part of the body is and how it is moving. Proprioception was developed by the nervous system as a means to keep track of and control the different parts of the body, using feedback from the movement of joints and muscles. It allows us to know where the edges of our body are – how far away we are from a wall, or how much pressure we are exerting on a pencil. Children with significant proprioceptive needs and decreased awareness of their bodies’ movements often seek out activities that provide them with increased awareness, such as grasping objects very tightly, or jumping onto pillows or furniture. They have difficulty knowing where their body is, in order to move it effectively. Proprioceptive input lasts around 2 hours – it provides both calming sensations to overactive children, and alerting information to under stimulated children.