Multiple Personality Disorder

This documentary is about Multiple Personality Disorder (i.e. people possessing multiple personalities that control the body separately).

This means these people often have blanks in their memory and can't remember what the "other personality" did with the body while they were "away".

It's a documentary absolutely worthwhile seeing.

If you watch the video you might notice some small astonishing details:

• In the case of the police officer, John, with Multiple Personality Disorder: John's dog "senses" whenever he switches to an "other personality" (the personality of a child in this case) and thus stops regarding him as his master. As a result the dog enters the living room - something he is normally not allowed to do by John. When John switched back to "normal" (i.e. non-child) the dog exits the living room.
• In the case of Barb (married and mother of 2 children): Whenever she switches to the personality of Mae (a 5 year old child) she doesnt seem to need her glasses anymore! Somehow her vision is then corrected.

So, how can a dog sense the change in personality?(just voice? behavior?)

And, how is is possible that when someone changes personality they would suddenly not need their glasses anymore?...

I thought that bad eyesight was something physical, not psychological... (?)