Sensory defensiveness refers to a behavioral
aversion or defensive response to stimuli that is generally considered non-noxious, occurring in one or more sensory systems
(Wilbarger & Wilbarger, 1991; Wilbarger & Wilbarger, 2006). It can be inferred that this behavioral response may result
from an over-responsive reaction of the evaluative system (also referred to as our protective system). While the cause of
sensory defensiveness is not yet known it appears to be affected by genetic, idiopathic, familial and environmental factors
(Kinnealey, Oliver & Wilbarger, 1995). Wilbarger & Wilbarger (1991, 2006) identify three levels of severity including
mild, moderate and severe, with differences occurring in the extremity of the response and the impact on daily function. Barenek,
Foster & Berkson suggested that sensory defensiveness consists of two subgroups; ‘Tactile defensiveness’,
and ‘Auditory and other’ (1997a, p. 183). Patricia Wilbarger has suggested that as many as 15% of the population
may be effected by sensory defensiveness (Wilbarger & Wilbarger, 2006; Kinnealey, Oliver & Wilbarger, 1995). Other
authors suggest that, while this disorder appears to be prominent, the actual number may be much less than 15% (Barenek, Foster
& Berkson, 1997b).
Individuals who exhibit sensory defensiveness
demonstrate unique, individualized responses to sensory input and may include patterns of avoidance, sensory seeking, fear,
anxiety and aggression (Wilbarger & Wilbarger, 2006, p. 2). These difficulties arise from inefficient processing of sensory
information however they are often misdiagnosed as being emotional in origin. While it is important to differentiate the different
origins and underlying dysfunctions of sensory defensiveness and emotionally based difficulties, it should also be noted that
sensory responses never occur in the absence of emotion. In fact, while the disorder in sensory defensiveness is rooted in
sensory processing, its ramifications if left untreated extend quickly into the domains of emotional and mental disorders.
Sensory defensiveness occurs from birth and has a negative impact on the developmental process.
Sensory defensiveness involves natural
responses to environmental triggers. In other words, the behaviors are typical defense behaviors in responding to threatening
stimuli. The difference is in the criteria the individual uses for responding. It may be appropriate to respond negatively
to a noise when alone in a dark parking lot but less natural when with a friend in your busy well-lit local store parking
lot; or responding negatively to rustling bushes when on a safari in Africa compared to rustling papers of a peer in a classroom.
People with sensory defensiveness demonstrate poor calibration of natural events that share qualities with natural triggers.
The experience of a tag of a shirt touching your back may share tactile qualities with the experience of a spider on your
back. However the typical response would be to notice the tag and habituate to it fairly quickly, or to not even notice it
consciously at all. A person with sensory defensiveness incorporating the tactile system would likely notice the tactile sensation
to a greater extent and have difficulty habituating to it. This particular scenario could lead to increased general arousal,
increased distractibility and refusal to wear certain clothing. Sensory defensiveness can intrude on all activities of daily
living. Ayres, referring to tactile defensiveness, stated that
“To the tactilely defensive child a simple touch on the arm may be a primal threat, just as it would be to an
animal that is not tame. The natural reaction to a primal threat is a primal response such as anger, fighting, or running
away” (Ayres, 1979, p.109).
In this statement, Ayres clearly demonstrates
that the response of the defensive child is quite natural given the way the child has interpreted the sensation. However,
as understandable as the response may be, it is likely to provide a great deal of stress on the individual with sensory defensiveness
and alone can lead to severe functional and social difficulties and can result in secondary difficulties as outlined below.
secondary to sensory defensiveness
People with sensory defensiveness may exhibit
a variety difficulties and coping mechanisms, secondary to the sensory defensiveness, that are common in other conditions
(Wilbarger & Wilbarger, 2006; Kinnealey & Fuiek, 1999; Kinnealey, Oliver & Wilbarger, 1995). These may include
social and emotional difficulties (e.g. avoidant or anxious in interactions), postural difficulties, cognitive difficulties
(e.g. memory) and physiological difficulties (e.g. diarrhea, constipation, digestive and gastro intestinal difficulties, reflux).
For this reason, identification and treatment of sensory defensiveness is crucial in understanding and treating these other
challenges where sensory defensiveness may mask the true abilities of the client.
Clients with sensory defensiveness tend
to demonstrate increased responsiveness and escalation of arousal, decreased habituation and recovery of arousal states as
well as unpredictable and changeable states (Wilbarger & Wilbarger, 2006). Miller noted that the over-responsive children
in their studies, when compared to the typical children, demonstrated larger and more numerous electrodermal responses (EDR’s)
as well as habituating more slowly to repeated stimuli than their peers (Miller, 2006; McIntosh et. al. 1999). While sensory
defensiveness is found in a variety of clinical populations, the research by Miller and colleagues suggests that sensory modulation
disorder, including over-responsivity or sensory defensiveness, appears to present as a discrete disorders with both differences
and commonalities with patterns of learning and behavioral disorders, such as ADHD (McIntosh et. al, 1999).
While it is generally accepted that individuals with sensory defensiveness tend to exhibit
a heightened general states of arousal, this may not always be the case. Julie Wilbarger suggests that sensory defensiveness
is a difficulty arising from the evaluative system of the CNS primarily and while individuals most often recognized as sensory
defensiveness tend to demonstrate a state of general arousal that is heightened, it is possible to demonstrate low general
arousal and also be sensory defensiveness (Wilbarger & Wilbarger, 2006). This should not be confused with individuals
who appear to have such heightened arousal that they ‘freeze’ or ‘shut down’, often referred to as
being in a state of sensory overload (Wilbarger & Wilbarger, 1991). Rather these appear to have a low state of general
arousal but exhibit a sensory defensiveness response to stimuli generally considered non-noxious. One presentation of this
child may be described as having a “narrow band” of optimal arousal, moving quickly from a low state of arousal
to a heightened state of arousal and having difficulty maintaining a state that would be optimal for the particular activity
involved in (Frick, Hacker & Jereb, 2001). Mayes, 2002, noted similar patterns of arousal in infants who had received
prenatal cocaine exposure.