Since I was only able to test the mockup with one person I contacted an expert to give his opinion on the application and check whether this can be used by most of the persons with a mental disability. When I showed the application the immediate reaction was really positive. He thinks this application can really be a way to close the social gap some more for a lot of people with a mental disability.
For the dilemma for the selection of text and then reading it out loud or the other way around the expert responded that it might be better to choose for first selecting and then reading it loud because in this way it is consistent with other reading applications like Sprint and Kurzweil which some of them already use. For the buttons then it might be a solution when tapped to just read it out loud anyway and also navigate to the page. Facebook does not really have a deep hierarchy of pages so going back to the previous page is not that difficult in this application.
Some other suggestions were to use sclera pictograms for the statuses with a sub hierarchy, like I feel… and when they select this you go to happy, sad,… The same could be done for some standard texts they could put on the walls of friends like: “I would like to…”, “Let’s go to…”,… Another nice thing would be the possibility to change font and font size, this preference (in the way the person can read it best) is really different from person to person.