One theory of autism is that of “mind-blindness,” developed by Simon Baron-Cohen. Out of this mind-blindness come a general lack of empathy. If you are mind-blind, you literally cannot empathize, after all.
Being a person with Asperger’s and having a son (Daniel) with autism, I both know what it’s like to have autism and to live with someone with autism. This is a quite different experience than studying autism in the lab, through surveys (of neurotypical parents), etc.
For example, when I am ill, Daniel doesn’t notice that I’m ill the way my neurotypical son, Dylan, or daughter, Melina, does. They immediately notice and show empathy. Daniel is still primarily interested in getting me to do whatever it is he’s interested in doing. Most would argue that this proves lack of empathy. However, something interesting happens when my wife points out to Daniel that I am sick: he immediately looks worried and asks me if I’m okay. When you direct his attention to how I feel, he shows empathy. And he will periodically ask me how I’m doing until I’m well again. Also, we have a set of doctor toys, and he will go get them and give me a “check up” with them to make sure I’m okay. If those behaviors aren’t empathy, I don’t know what is (of course, my being autistic myself might mean I don’t in fact know what empathy is — but my answer to that is the same as that of George Takai on an episode of The Big Bang Theory when he was questioned as to how he could know anything about what a woman wants: “I read!”).
In any case, this at least has the surface appearance of empathy. And I do in fact feel bad when my wife feels bad, and seeing her in pain induces feelings of pain. More, when my father lost his left arm in a mining accident when I was in high school, I experienced sympathy pains. Now, I will also admit that I don’t always come across as the most empathetic person — but that might be due to what I suggested with my son: I probably need my attention brought to the fact that the person is suffering. I am quite sensitive to suffering in general — it affects my politics and support for free markets — but I sometimes miss it in person.
Missing someone’s suffering is part of the general problem of being constantly bombarded with information. It can be distracting. If there is any amount of noise in the house, I have a hard time hearing the television. While neurotypicals have the ability to cut off all but what they are trying to pay attention to — indeed, can make background noise just that: background — I hear the background noise at at least the same level, or higher, than what I want to pay attention to. Thus, I have to turn the T.V. volume up quite a bit. When there is nobody in the house, I can hear the T.V. at a volume of 30; when people are in the house, I have to have the volume up to at least 70, and I may have to have it all the way up to 100. And I’ll still have to tell people to please quite down so I can hear.
This happens too when I am in public, at say a Starbucks, with a friend. My eyes are all over the place, noticing everyone and everything. At the same time, I am able to remain focused on the conversation. The distraction is thus sense-dependent. I can be visually distracted and pay attention to what you say. I can have auditory distraction and think and write. (I can even think while talking under the right conditions.)
Since much human communication is through visual cues, the fact that I am often visually distracted while I’m supposed to be focused on you, I can miss those visual cues you are communicating to me. This can result in socially awkward situations and an appearance of a lack of empathy on my part.
If this sounds a lot like attention deficit disorder, that may not be a coincidence. Many with autism are also diagnosed with ADD. I would not be surprised if ADD were in fact part of the spectrum, if we were to extend the spectrum out beyond Asperger’s. Mere ADD does not result in missing social cues — or at least, not as many as are missed by those with autism — which is what keeps it outside the autism spectrum, but I must wonder if it is not unrelated. I will also note that, like autism, far more boys have ADD than do girls.