The Eight Sensory Systems, Explained
The great eight and what they do
Even as a young child, you likely learned about the “5 senses” at school: seeing (visual); hearing (auditory); smelling (olfactory); tasting (gustatory); and touching (tactile). Whether they are present, absent or not functioning optimally, these sensory systems all play pivotal roles in our experience of the world and how we respond to it. In addition to these senses are ones that most of us did not learn as children, these being the vestibular system (i.e., movement and balance), the proprioceptive system (i.e., body awareness in space), and the interoceptive system (i.e., the ability to feel what is happening inside our body). In total, there are actually eight senses of human perception that we can currently name, discuss and treat.
Visual System
The visual system allows us to detect color, shape, orientation and motion. The primary visual area of the brain is located in the occipital lobe, although other portions of the brain are involved in the processing of visual information as well. Sensory deficits often noted in the visual system can include difficulties with ocular motor control as well as a decreased ability to visually process information.
Signs of visual system dysfunction include:
- Difficulties discriminating between/among shapes, letters, etc.
- Appears sensitive to light
- Difficulty with eye contact
- Trouble finding things, even when in front of them
- Hesitant on stairs
Auditory System
The auditory system is responsible for hearing. It allows us to detect changes in sound frequency or amplitude, and allows us to process verbal language. Concerns with this system often warrant an evaluation of an audiologist to rule out Auditory Processing
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Disorder (also known as Central Auditory Processing Disorder).
Signs of auditory system dysfunction include:
- Difficulty understanding spoken language, particularly in noisy environments
- Difficulty localizing sounds
- Frequent requests for repetition (including “Huh?” and “What?”)
- Does not remember what they’ve just been told
Olfactory System
The olfactory system is responsible for processing smell. The olfactory bulb, located in the brain, transmits smell information from the nose to the brain. It discriminates among odors, enhances detection of odors, and often receives information from higher levels of the brain to process the information it receives.
Signs of olfactory system dysfunction include:
- Reduced ability to detect odors
- Sensitivity to smells
- A change in the normal perception of odors
Gustatory System
The gustatory system provides us with our sense of taste. It allows us to distinguish between safe and harmful foods, such as meat that has spoiled or dairy products that have gone sour. As a result of the process of evolution, salty and sweet foods are generally regarded as pleasant foods, while sour and bitter foods are less appealing. This is theorized because salt provided a critical element for the human body and sweet tastes indicated foods that would provide energy when food was scarce, while sour tastes could indicate spoiled foods containing bacteria and bitter tastes could protect humans from poisonous plants/substances.
Signs of gustatory system dysfunction include:
- Reduced ability to taste
- Reduced ability to smell (as smell and taste are linked)
- Loss of appetite
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