How to write Science Fiction & Fantasy, by Orson Scott Card, pp.92--94:
... I think of a story by Tom Maddox that appeared some years ago in Omni. In the first of second paragraph he had passengers taken from their airplane to the terminal on what he called a "reptile bus." I was teaching an sf literature course at the time, and my students were pretty evenly divided between those who had been reading sf for years and those who had never read it before that semester.
The majority of the experienced sf readers reported the same experience I had: At least for a moment, and often for quite a way into the story, we thought that Maddox wanted us to think that reptiles were somehow being used for airport transportation. We pictured a triceratops with a howdah, perhaps, or an allosaur towing a rickshaw. It was an absurd sort of technology, and it would have strained credulity -- but many sf stories use such bizarre ideas and make them work. Maddox might have been establishing a world in which bio-engineers had created many new species of very useful but stupid dinosaurs.
Those who had never read sf, however, were untroubled by such distractions. They knew at once that "reptile bus" was a metaphor -- that it was a regular gas-burning bus with several sections so it snaked across the tarmac in a reptile like way.
... Do recall the difference between metaphor, simile, and analogy. Similies and analogies, which explicitly state that one thing is like another thing are available; it's only metaphors, which state that one thing is another thing, that are forbidden. "You could treat Howard Merkle like dirt and he'd still come fawning back to you, just like a whipped dog," a similie, is perfectly clear and usable in speculative fiction, whereas the metaphor "Howard Merckle was a dog, always eager to please no matter how you treated him" is problematical early in a speculative fiction story, because it could be taken literally.
"Autobiographical writings" by Margeret Dewey from the book Autism and Asperger syndrome, edited by Uta Frith, pp.237--238: (Note: for "theory of mind", consider how the meaning changes if you substitute "theory of how non-autistic minds work")
... Another interesting feature of the writings upon which Relevance theory sheds some light is our authors' use of metaphor, simile and irony. According to Relevance theory, similies can be understood at a purely literal level -- saying 'He was like a lion' is no different from saying 'He was like his father'. In both cases the hearer is set the task of deciding in what respect there is a similarity. We would therefore predict that even autistic speakers who lack a theory of mind should be capable of using and understanding similies. And indeed we find many examples of simile in the works of our three autistic writers. For example, Temple writes: 'relations between people are like a glass sliding door. The door must be opened gently, if it is kicked it may shatter' ('My experiences', p. 145). Barry too uses similes, for example, he says about having a new girl-friend: 'I think it wouldn't be wise behaviour to both spend money on her and practice behaviour with her at the same time. It's like you cannot build the roof of a house first then the foundations later.'
Metaphor, on the other hand, requires some understanding of intentions. In a metaphor the propositional form of the utterance is a more or less loose interpretation of the speaker's thought. Therefore metaphors cannot be fully understood or properly used without a first-order theory of mind -- using a default value of literalness will not work. Not surprisingly, then, examples of metaphors are much harder to find in the writings. Temple, for example, seems to have a tendency to take metaphors literally -- as in the 'I am the door' example. Rather like examples of humour, metaphors are conspicuous by their absence. Barry does use some metaphors, in passages of the letters which appear to be parroted, but in a strange way: 'I read an article on the trouble of our transportation. They are finding cures for the illness of our transportation. Transportation has been getting sicker every year.' Interestingly, Mary Barnes, the schizophrenic writer quoted above, often uses rich and evocative metaphors in her book, for example, she writes: 'Slowly I worked free from the past, from the web... A whole lifetime could be spent making, outside oneself, webs to match how one is inside. To go into madness, to start to come out, to leave the web, is to fight to get free, to live ...' (p. 162).
... Relevance theory can lead us to make some non-trivial and non-intuitive predictions about autistic language use -- and, with theory of mind explanations of autism, may help us to understand many of the features of our autistic authors' writings. In addition, Relevance theory may shed light on other elements of autistic behaviour not explained by a lack of theory of mind. For example, I have mentioned the poor understanding we have of obsessive behaviours and interests in Asperger syndrome. One explanation may be that these behaviours are a consequence of the failure to calculate relevance normally, and part of the autistic person's odd focus of attention. Imagine, for example, if the driver of a car paid as much attention to the position of his seat-belt as to what was going on in the road in front of him. Or if someone placed as much importance on the fact that their lunch was late as most people would on the very late return of a loved one who is usually prompt. Such odd focusing of attention would appear obsessional. It may be, then, that it is not the degree of attention or anxiety, but its odd focus and subject -- the peculiar attachment of importance to apparently irrelevant things -- that makes the autistic person seem obsessive. Much the same point could be made about the incidence of fixations in autistic people -- it may be the oddness and incompleteness of their interests that earns this label rather than any great difference in passion between them and the normal train-spotter. A child who talks about electricity pylons all the time is more likely to be thought oddly fixated than one who talks about horses or football teams. Such phenomena as obsessions and fixations may be seen as in part a result of the breakdown of normal relevance.
Also note how Orson Scott Card, in typical autistic fashion, gives an example from his own experience to describe a general principle :-P.
Another somewhat unrelated likeness... The three children in Orson Scott Card's book "Enders Game" also show many signs of Asperger's syndrome, including isolation, overreaction to teasing, and in Peter's case malice similar in form to that noted in Asperger's initial paper.