If you watch "The Biggest Loser", then you are aware that the contestant Dave has a daughter with Rett Syndrome. On the clip where he talks about his family, he says: "As for her mental capacity, she's between a year and eighteen months old mentally". I am ecstatic that Rett Syndrome is out there and more people are hearing about it. However, I want everyone to understand that Rett Syndrome does not cause these girls to be stuck at a mental capacity of 1yr - 18 months. This may be true for his daughter, but not for Rett Syndrome in general. It has been shown that these girls understand everything. They are smart and they are able to respond and answer you if you give them time. Because of their apraxia (inability to control their body/arms/legs) it may seem like they don't know how to respond correctly.
The only reason I am coming out and defending Rett Syndrome is because we want everyone to treat our girls like you would any other child their age, not like they are 1yr - 18 months.