About the Senses

You can likely name the five senses: sight, smell, sound, taste, and touch. But did you know humans actually have as many as 8, 21, or even 33 distinct senses? Researchers are still debating what constitutes a sense. However, we do know our senses are tied to almost everything we do.

Eight Sensory Systems | Sensory Processing | Issues with Sensory Processing | Who is Affected | How Sensory Processing Issues Display | Our Approach | What We Are Doing To Help

Eight Sensory Systems

There are eight prominent sensory systems acknowledged by Occupational Therapy (OT) profession and Twenty-One Senses. Click below to learn more about each sense, how issues may appear for that sense and how to help support an issue.


The visual system is responsible for the body’s sense of sight.


The olfactory system is responsible for the body’s sense of smell.


The auditory system is responsible for the body’s sense of hearing.


The gustatory system is responsible for the body’s sense of taste.


The tactile system is responsible for the body’s sense of touch.


The vestibular system is responsible for the body’s sense of balance, motion, and spatial orientation.

External Body Awareness
External Body Awareness

The proprioceptive system is responsible for the body’s external awareness.

Internal Body Awareness
Internal Body Awareness

The interoceptive system is responsible for the body’s internal awareness.

Sensory Processing

The human brain processes information from the eight sensory systems. Some examples of the brain properly processing sensory input is how you know to put on a jacket, use the restroom or can successfully walk from pavement onto rocks.

Everyone is affected by sensory input. Have you ever felt a twinge of pain during a loud movie or become a little overwhelmed while shopping in a bright, busy store? The average human can have some degree of sensory sensitivity or craving, even if they don’t realize it. Do you chew on your pen while working, prefer clothing with specific textures, or love riding roller coasters? Each of these are the result of the way your brain reacts to sensory information, often without you even noticing.

Illustration of how the human body processes sensory information.

Issues with Sensory Processing

Sensory processing issues occur when there is a breakdown in how the brain translates the sensory information provided from the central nervous system. The brain may fail to recognize, misinterprets, or responds inappropriately to the input. It’s estimated that 1 in 20 people have some sensory processing issue and 1 in 6 children are affected by sensory issues in their daily activities.

Illustration of how the human body can have issues processing sensory information.

Who is Affected

Sensory processing issues can be a standalone diagnosis of Sensory Processing Disorder (SPD). However, an individual can be affected by sensory processing issues, without having a SPD diagnosis. Many other diagnoses can include a component of sensory processing issues. Some of these diagnoses are included below.

  • Autism Spectrum Disorder (ASD)
  • Trauma (Simple, Chronic & Complex)
  • Anxiety
  • Down Syndrome
  • Oppositional Defiant Disorder
  • Misophonia
  • Allodynia
  • Upper Respitory Infections
  • Visual Processing Disorders
  • Hyperacusis
  • Obsessive-Compulsive Disorder (OCD)
  • Attention Deficit Hyperactivity Disorder (ADHD)
  • Migraines
  • Pregnancy
  • Fibromyalgia
  • Fragile X Syndrome
  • Lyme Disease
  • Temporomandibular Joint DIsorder (TMJ)
  • Speech & Language Disorders
  • Audio Processing Disorders
  • Adjustment Disorder
  • Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDA)
  • Post Traumatic Stress Disorder (PTSD)
  • Depression
  • Concussion
  • Tay-Sachs Disease
  • Selective Mutism
  • Prader Willi Syndrome
  • Meniere’s Disease
  • Vertigo
  • Motor Processing Disorders
  • Global Developmental Delays

How Sensory Processing Issues Display

Sensory processing issues can display differently from person to person. A person may have different responses, depending on the sensation (ie sensory system). For example, a child may craves touch, but avoid loud noises. A person’s response to a sensory processing issue will display as one of the following:

Sensory Craver
Sensory Craver

AKA – Sensory Seeker

Sensory cravers, or seekers, have an inexhaustible appetite for sensory stimulation. They may be constantly seeking out bright lights, loud music, certain textures, or physical contact with others.

Seekers may seem to need constant stimulation. However, they tend to become more deregulated as they take more input.

Sensory Over-Responsive
Sensory Over-Responsive

AKA – Sensory Avoider

Over-responsive individuals, or avoiders, feel overloaded and overwhelmed by their senses. They may be bothered by faint smells, changes in temperature, or background noises others can’t detect.

Avoiders often have extreme or upsetting reactions to even very mild stimulation.

Sensory Under Responsive
Sensory Under Responsive

AKA – Sensory Challenged

Under-responsive individuals have difficulties detecting, understanding, and responding to sensory stimuli such as sound, light, or touch. 

Sensory Challenged can affect one’s ability to detect, interpret, and recognize the sensory input.

Our Approach

When a child engages in community activities, they often encounter crowds, loud/unpredictable noises, bright lights, unusual/strong odors and other sensory input from all around them. Children with sensory processing issues do not respond to everyday sensory information the same way most people do. As a result, research has shown that these children tend to be withdrawn, show signs of anxiety or depresseion, struggle socially and have difficulty fitting in with their peers.

Twenty-One Senses chooses to stay diagnosis agnostic, as we believe that by focusing on sensory, we are able to help more people irregardless of their diagnosis. Because sensory processing issues are so widespread, increasing sensory awareness and accommodations can have a tremendously positive impact on the special needs and trauma communities as a whole. Our mission is to teach communities to support the inclusion, dignity, and well-being of the ~17% (one-in-six) of their kids, customers, colleagues, and peers currently living with invisible sensory issues.

What we are doing to help