Ever heard of the Sally-Anne experiment? It's a simple puppet show. It's meant to demonstrate whether you understand what's called the "theory of mind." And it's raised a lot of questions and a lot of ire.
The Sally-Anne Experiment started out as a story, but was developed into a puppet show in the 1980s. It's a twisted tale of deception, and it's point is to find out if the viewer realizes that someone was deceived. Two characters, Sally and Anne, stand onstage. Sally has a basket. Anne has a box. On stage is a marble. Sally takes the marble and hides it in her basket. Then she goes out for a walk. While she's gone, Anne takes the marble and hides it in her box. Sally returns.
The viewer is asked, in various ways, where will Sally look for the marble? Will she look for it in her own basket, or in Anne's box? As long as we assume these are human characters, we know that Sally can't possibly know that Anne took the marble, and will look in her own basket. That's not always the answer people give.
In a study done on a group of kids, some of which were neuro-typical, some of which had Down's Syndrome, and some of which were autistic, the autistic kids had the most trouble realizing that, although they knew that the marble was in the box, Sally didn't. While the neuro-typical kids and kids with Down's syndrome both overwhelmingly answered correctly, the kids with autism overwhelmingly answered that Sally would look in the box. As the times progressed, the test was given to others, including nonverbal kids and autistic adults, not by asking for responses but by watching where they directed their gaze. Children still looked at the basket more than the box. And even autistic adults looked equally at the basket and the box.
The question is, what does this mean? Some argue that autistic children and adults have a difficult time developing a "theory of mind." They can't understand that other people have different knowledge and different emotions than they themselves do. So it doesn't occur to them that, even though they know something, other people don't.
Others disagree, and have tests to back them up. Under most criticism are the studies that analyze where the viewer of the Sally-Anne experiment looks. Some tests showed that autistic people, especially adults, would look at the box, or both at the box and the basket, but when asked where Sally would look, they would answer the question correctly. Other tests indicated that autistic kids do understand and communicate the correct answer in simpler variations of the experiment that show they have a theory of mind, but can't answer the more complex question. This indicates that autistic kids can develop a theory of mind, but can't parse the questions that come at them during the Sally-Anne experiment. The Sally-Anne test is still routinely given, both to test cognitive development in general and as one of the tests that are sometimes used to diagnose autism. It looks like it can be helpful in identifying which people have autism, but not necessarily in establishing what autistic people think.