Autistic inertia is an inability to change task or focus – imagine a person totally wrapped up in doing one thing, like reading a book, who finds themselves incapable of putting the book down in order to go and make themselves a nice cup of tea. They want the tea, they’re fine with the theory of making the tea and the book isn’t necessarily gripping, but the required change of focus from the book’s leaves to the tea leaves is just too much.
