I think "lack of imagination" is a very misleading phrase. Clearly, many Aspies have amazing imagination, easily imaging things in completely different ways than the rest of the world does, and contributing some of mankind's greatest inventions.
What most AS seem unable to do, however, is move off a script of their own making, to experience and follow one of someone else's making. Once on a path, they often lock firmly onto it. Think of movie directors that the press have referred to as "tone deaf" towards criticism of their art. Or inventors who spark the great ideas, but can't run with them for want of a needed adaptation that they refuse to accept (why Bill Gates got rich but it all really was someone's idea to start with). Or why if plan A and plan B don't work out then you may as well give up, because you can't on the spot think up plan C. I guess all that is still appropriately called "imagination," but it is a very different kind of imagination than what creates amazing stories and invents new ideas. Maybe a better term would be adaptive imagination?
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Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).