More on stereotypical patterns

‘Restricted/stereotyped, and repetitive patterns of behavior/interests’ are among the core features of autism.

An ‘anxiously obsessive desire for the maintenance of sameness’, as formulated in the article by which Leo Kanner published his ‘discovery’ of autism in 1943, is part of this feature. Particularly children can get panic-attacks when a detail in their environment has changed.

Examples of behavioral characteristics are: interest in parts of objects, preoccupation with topics or intense interest in details, stereotypical movements (e.g. rocking, flapping, twirling), preoccupation with tasting and smelling objects, unusual response to sounds and a strong insistence on routines.
It is often assumed that these behavior are (also) an effort to compensate for other troubles. Such as with visual orientation where rocking and flapping is an effort to rely more on the sense of proprioception.     

These characteristics mainly describe (very severe) autism in the original sense, as described in the DSM-IV under ‘autistic disorder’ (‘kanner-autism’). This category has receded somewhat into the background after the spectrum-diagnosis was widened to include Asperger’s syndrome and PDD-NOS (‘pervasive developmental disorder not otherwise specified’).
In milder and much milder forms than ‘kanner-autism’ some of these same characteristics can however be present in most people on the spectrum. Rigid patterns of thinking and obsessive behaviors may be the most common features.

An example of a consequences for autism-friendly design is the recommendation to make the interior of a living room as stable as possible and give furniture fixed places. Another are adaptations in the bathroom, so one can act ritualistically without bothering other family members. A third example is that one may take an obsessive interest in what can be seen through a window, such as traffic, trees or airplanes.