Autism, if you see it as a collection of traits, is caused by where our attention goes. Autism, if you see it as a neurotype, is a way to define where our attention goes.
In either case, attention is at the root. Autistic people tend to notice spoken language more than body language and tone. We notice surprising sights and sounds more than consistent ones, and pay more attention to sensory input in general than the average person does.
Everything else about autism is downstream of this. We miss social cues because we take people literally. We move in a rhythm because it soothes our overstimulated senses. We experience anxiety (and sometimes trauma) from sensory shock and unexplained rejection. We turn to predictable foods, objects, phrases, and interests because they shield our bodies from shock and our minds from mystery.
Some autistics, in some circumstances, can learn to notice some of the things we naturally ignore. But it’s easy for non-autistics to forget that we aren’t just replacing one focus of attention with another. Rather, we’re adding more kinds of information on top of what we naturally notice.
That can feel super overwhelming. Meltdowns and shutdowns, which are often listed as autistic traits, are downstream of the overwhelm we feel when our attention is pulled in too many directions.
Neurologically, autism is more complicated than this. But if you want to understand why autistic people do what we do, and predict what we’ll do next, it helps to think of autism as an atypical form of attention.