I realise that at a severe level this can present as a symptom of Asperger's Syndrome, or High Functioning Autism. But I am not talking about that.
I am referring to people who just don't seem to understand irony. For example, let's say we have a doormat outside our house with the words 'BEWARE OF THE OLD WOMAN' written on it.
I think most people, at least in Britain, would see it as a joke. But some, at the extreme, might expect to meet a fierce old lady. Other's, less afflicted, might think it was a severe instance of political incorrectness. What do we call someone who just doesn't see the joke?
Or let's say that someone comes to dinner and is thoroughly miserable all evening, and the host or hostess just does not pick up on the fact that it is because of a difficulty that the guest has in their lives.
Do we say 'Penelope is 'insensitive'? No that isn't quite the word is it? Because had Penelope understood the reason she would have been as sympathetic as the next person. It was just that it simply never occurred to Penelope that her guest might be feeling sad about something, that she, the guest was not able to talk about. There are people who just don't pick up signs around them. Metaphorically they have no peripheral vision. They only see the obvious, and what is straight in front of them.
How do we describe such people?