Most of them do not rest as long as they should because they do not have a sense of time.
Note cards are better than books or calendars for looking at pictures because they are a smaller size and easier to hold. Another advantage is that they can be handed to the person, even while walking, which may help capture and sustain their attention. These pictures are a good example of a single subject foreground and a minimal background that help the person focus their attention on the information that they are able to process.