A somewhat new hypothesis:
The Intense World Theory states that autism is the consequence of a supercharged brain that makes the world painfully intense and that the symptoms are largely because autistics are forced to develop strategies to actively avoid the intensity and pain.
Here’s a more extensive explanation.
This hypothesis connects many of the sensory peculiarities of autism with the attentional and social ones. Those had seemed like puzzling correlations to me until now.
However, it still leaves me wondering why the variations is sensory sensitivities seem much larger with autism. The researchers suggest an explanation involving increased plasticity, but I don’t see a strong connection between the Intense World hypothesis and that.
One implication (from this page):
According to the intense world perspective, however, warmth isn’t incompatible with autism. What looks like antisocial behavior results from being too affected by others’ emotions—the opposite of indifference.
Indeed, research on typical children and adults finds that too much distress can dampen ordinary empathy as well. When someone else’s pain becomes too unbearable to witness, even typical people withdraw and try to soothe themselves first rather than helping—exactly like autistic people. It’s just that autistic people become distressed more easily, and so their reactions appear atypical.