You guys, I have given this 'autistics lack a sense of humour' myth a bit of thought lately. I was always square against it, because I was raised by a mother who made me appreciate the importance of going through life with a sense of humour, made me understand sarcasm, and always told me to not take myself too seriously.
However, I have noticed that, when I'm on the receiving end of jokes, sometimes practical jokes, sometimes verbal, I won't be too responsive, and when I do respond it's either with annoyance or misunderstanding. Also, some jokes that people tell me, I'll have the same response. I think this may well be related to my autism, judging from anecdotes I have read in the past here on Wrongplanet. Sometimes, a joke will require one to not take it too literally, and a problem autistic folks have sometimes, is taking things literally. There was this one time when a particularly frivolous co-worker of mine went out for a smoke (+/- 10 minutes or so), and said to me and my ther coworker "Want to write down my phone number, so you can call me when you need me?" The JOKE here was that it was a very slow day with very few customers, so he facetiously suggested that we might get busy in our workload- which we wouldn't. This happens A LOT to me.
So the taking stuff literally on top of the being annoyed at or unresponsive to certain jokes, may lead the average person to think that autistic people lack a sense of humour.
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clarity of thought before rashness of action