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The Role of Sensory Perceptual Differences in Autism:

The Intense World Syndrome and other ‘sensory theories’

Although already in the very first descriptions of autistic children, researchers mentioned unusual sensory responses (‘abnormal’, ‘odd’, ‘bizarre’) – Kanner 1943; Asperger 1944; Eveloff 1960, Rimland 1964; Ornitz 1969; Wing 1972, Delacato 1974, etc. and sensory hypotheses to account for autism were put forward (e.g., Bergson & Escalona 1949; Ornitz 1969, 1974), from the 1970s onwards, the main focus has been on the cognitive development of autistic children, and different theories of cognitive deficits have been formulated, e.g., lack of ToM (Baron-Cohen, Leslie, Frith 1985), the WCC (Frith 1989) and the executive dysfunction theory (Ozonoff 1995). All these theories suggest that low-level perceptual processes are intact in autism, and information processing up to the point of interpretation by a central system can be assumed to be normal in an autistic person (Frith).

Since 2000s, research studies have provided evidence that autistic individuals have a range of perceptual processing differences, and several ‘sensory theories of autism’ have been proposed, e.g., ‘sensory gating deficit’/gestalt perception, and an imbalance of cortical excitation and inhibition (Rubenstein & Merzenich 2003).

The ‘intense world syndrome’ interpretation of autism (Markram et al. 2007) suggests that the autistic person may perceive their surroundings as overwhelmingly intense (due to hyper-reactivity of sensory areas) and aversive and highly stressful (due to a hyper-reactive amygdala, which makes quick and powerful fear associations with usually neutral stimuli). In this view, autism is characterised by hyper-functionality as opposed to hypo-functionality as is often assumed. The Markrams & Rinaldi (2007) show how excessive neuronal processing lead to hyper-perception, hyper-attention and hyper-memory.

Hyper-reactivity and hyperplasticity mean that minicolumns (the smallest units of the brain capable of processing information) have a higher than normal capacity for processing information. Excessive processing of the sensory input in the microcircuits leads, in turn, to exaggerated perception, producing extremely intense images, sounds, smells and so on. This sensory overload, combined with inability to filter information (Gestalt perception) causes autistic children to withdraw and miss the opportunity to develop shared conceptual understanding of the world. Impaired social interactions and withdrawal are thus seen as the consequences and not the core features of autism*.

“If you were being FOREVER forced (at times none too patiently) to do upsetting functions or at times acutely painful ones, just because everybody else does it with no discomfort, AND expects you to be the same; would that make you outgoing, and a party personality? Or, would you turn away from your tormentors, acting as if you were uncomfortable or afraid or possibly frustrated with them?” (Morris 1999)

Bob Morris develops his argument further, showing that attempted use of different sensory mechanisms by a baby without any help from a perceptive carer to sort out and deal with these differences (both problems and abilities) may aggravate the condition. The earlier the carer understands the differences and accommodates the person via the appropriate intervention, the more likely the individual will become fully functional, but significantly different (in talents and thinking).

I prefer the metaphor of Parallel Sensory Perceptual Worlds, which unites all the sensory theories: Though autistic people live in the same physical world and deal with the same ‘raw material’, their perceptual world turns out to be strikingly different from that of people without ASDs. All these experiences are based on real experiences, like those of people without autism, but these experiences may look, sound or feel different, or they may be interpreted differently.

We think about the world in a way we experience it and perceive it to be. Different experiences bring different knowledge about the world. So how can we be sure that we are moving in the same perceptual/social world if our reconstructions of it are so different? How can we know that only ‘our perceptual version’ of the world is correct and theirs is wrong?

Some autistic individuals are able to perceive much more than any average ‘normal’ person. This ability comes with a price – they are easily overloaded in ‘normal’ situations and their cognitive and language development follow a different route (and, as the consequences, lead to social interaction and social communication problems), and the world they know (construct) is very different from the conventional one.

Though the manifestations of sensory perceptual differences vary in different people (no two autistic individuals have the exactly same patterns of sensory perceptual experiences) or even the same person at different ages), it is possible to establish the common features, and identify compensatory strategies and adaptations.

Numerous individual differences, indicating possible subtypes based on different patterns of sensory perceptual problems, have been reported (e.g., Greenspan & Wielder 1997; Lane, Molloy and Bishop 2014). Autism severity and developmental functioning vary depending on sensory differences, e.g., increased sensory differences were associated with increased autism severity and a lower IQ (Ausderau et al. 2013).

Better understanding of sensory processing in autism will assist in improving diag­nostic instruments (including diagnosis in very young children) and distinguishing sensory perceptual subtypes of autis­tic individuals. and provide appropri­ate choices of help needed by each particular individual.

In autism, any of the senses (or a combination of the senses) can be affected, bringing differences in interpretation and conceptualization of the environment they live in. In order to live in the same perceptual world (and to move in the same direction) we have to learn to switch from ‘our’ perspective to theirs.

Those who live/work with autistic individuals have to learn to switch perspectives and imagine what’s the world is like from the child’s perspective, in order to join the child ‘on his/her territory. Always try to imagine how the child sees, hears and feels. the world. (The difficulty of this exercise lies in our ‘normal’ sensory functioning.)


* The absence of ‘filters’ can lead to sensory flooding and may result in sensory deprivation with serious consequences.

Sensory deprivation can cause immediate problems and if it goes on for 20 or more hours it can cause long-lasting psychological damage which amounts to post-traumatic stress disorder (Forrest 1996). There are two different possible scenarios, both leading to sensory deprivation. Autistic individuals’ senses seem to be either ‘too open’ (‘no filters’) or ‘not open enough’ (not enough sensory stimulation comes in). The former results in defensive adaptations, such as systems shutdowns (when a child shuts down his/her senses to avoid painful experiences), that, in turn leads to self-imposed sensory deprivation:

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