First, autism is a behavioral diagnosis; it is not a description of the disability that drives those behaviors.
Imagine if blindness were defined as it's behaviors: it would be called something like 'Buumping-and-Groping-about Syndrome', or 'BUGS' for short. In fact, if no one had eyelids, then most sighted persons would never realize on their own as to what really drives the behaviors of this 'BUGS'.
"But,", you may say, "autism most certainly is a disability, because those who have it are disabled. If autism isn't a disability, then what is it?" I'm glad you asked.
To borrow a line from the cartoon ogre, Shreck, autism...
"is like an onion: it has layers..."
Try this: count a large pile of pennies one-by-one while two persons each whisper a different set of random numbers in your ears, each person to an ear. Did you struggle to keep track of your count? Did you lose count and have to start over? Were you unable to count all the pennies no matter how hard you tried? If you had enough trouble doing this, then imagine these two persons whispering their respective random numbers in your ears with the most emotionally persuasive voices they can manage. If you had any trouble at all with this, then imagine the whole world outside your head is like these whispers. In fact, it is. You just don't notice.
Atmospheric pressure is a simple example of that 'whispering world'. You aren't aware of atmospheric pressure, but if you're properly educated you know it's there. The reason you aren't aware of it is because the pressure inside your body equals that outside you. In other words, your internal pressure is normalized to the external pressure. The reason you don't feel it is because your brain is normalized to it as well. Nevertheless, that pressure is a force which impinges upon your body's efforts to remain alive-and-functioning.
An easy way for an air-pressure-normalized person to sense the pressure of the external air is to analyze his or her senses of breathing. For example, if you inhale deeply while simply sitting there reading this, you may actually feel the effort to breath. It is an effort of which you are not normally aware, because, just like to the atmospheric pressure, your brain is normalized to it.
But, if you continue to analyze this breathing thing, you may find that it is not necessarily as simple as it seems. Just the location of the sense of the effort is complicated. Not only do your lung muscles make an effort, so do those of your rib cage, abdomen, and deep internal parts. In other words, breathing is a highly complex, coordinated effort. Of course, you might make your lungs take in and expel a little air by contracting and relaxing merely your belly muscles. But, that's far too much work for so little air! And, seemingly contrary to that exclaimed statement, you can breath without expanding your belly, but only by making an effort of contracting your belly muscles. As I said, it's complicated.
Many people have the impression that their effort to breath is mainly in their throats. They have this impression for two reasons: One, their throats feel much more than their lungs, feeling not only the pressure when they hold their breath by closing their throats, but the movement, and the evaporative 'temperature', of the air as they breath; Two, they normally breath without making any special effort to do so, so that the only part of themselves which they have any sense is involved is their throats.
This normalized sense that breathing is mainly in the throat is similar to how an experienced driver normally is aware only of what he sees as he drives, his other parts involved in the driving seeming to him not to exist. Fortunately for him, he is a competent human, not just a competent driver, because he never finds himself in a ditch for the occasional impulse to dance to the music on the radio. He has the ability somehow to keep track of his whole body despite that he is virtually unaware of it being there for the simple reason that he can't feel the bee which has just now begun trekking up his bare left calf. In fact, he can do all this while contriving an excuse to his boss for why he is late for work. When he finally sees the bee, and it just then stings him in the thigh seemingly out of spite, he still doesn't lose track of the fact that the traffic light has just turned green. Because, if he can make it at least to a certain morning meeting with the boss's boss, he might easily be awarded a huge raise for his outstanding research on the reputed nearsightedness of bees.
That amazing driving is brought to you by the brain's ability to be selectively overwhelmed. But, the difficulty many people have in the task of counting that pile of pennies is brought to you by that same ability. The catch is that the brain is not a random collection of interests. There is nothing particularly random about living either in the world inside, or outside, your head. Things matter, and different things matter to different degrees, each thing even shifting in its importance depending on what really is going on. As a socially normal person, making an exact count of a pile of pennies normally isn't nearly as important to you as is a human voice, even if that voice is speaking meaninglessly random numbers in your ear.