Ethics of user testing and people with cognitive disabilities

[Chair hat off]

In a previous thread the issue of user testing with people with 
cognitive impairments has been brought up. I thought this could be a 
good time to
share some of my own thoughts in this area. As some of you may know, I 
ran a user testing lab in the National Council for the Blind of Ireland 
for around 10 years. During that time I ran user tests with a wide range 
of users, not just those who are blind/VIP. In that time I did a small 
amount of testing with people with cognitive impairments, mental health 
issues etc. I found this a difficult group to test with due to my own 
concern about the ethics of doing so properly.

One very strong reservation I have about this whole area is simple. Does 
the user have the ability the objectively separate the tasks they are  
asked to perform in a test (and the natural success/failure when trying 
to completing these tasks) from their overall 'sense of self'? What I 
mean is that will the user be able to realise that their actions are 
being objectively observed without any 'judgement' on their performance?

  I would hate to think that a user would come away from a user test, 
where many tasks were failed (which is great usability information) but 
feeling worse about themselves, or as if _they_ were some kind of 
failure. In short, I think user testing is a bit of a performance, 
within an utterly contrived environment. Some people take to this well, 
others don't.

This is a very thorny issue but one I want to flag. I don't think 
testing should take place at all without a strong framework about how to 
deal with these sensitive situations. Sometimes you may have to make a 
call not to test, if it isn't in the best interest of the user test 
participant, even if they may be a perfect candidate for 'rich data'. 
I've made this call not to test in the past, and my overall take away 
was that I am largely uncomfortable doing this kind of testing, unless 
I'm sure it is in the participants best interest, separately from 
whatever the secondary need of a project/client is.

Thoughts?

Josh