The reason is to prevent the voluntary participant from later claiming that their participation was involuntary and telling that to the IRB.
‘Well if your participation was involuntary, why did you sign this document?’
It kind of limits the arguments someone could make attacking the ethics of the study. The attacker would have to allege coercion on the order of people being forced to lie on forms under threat.
The reason is to prevent the voluntary participant from later claiming that their participation was involuntary and telling that to the IRB.
‘Well if your participation was involuntary, why did you sign this document?’
It kind of limits the arguments someone could make attacking the ethics of the study. The attacker would have to allege coercion on the order of people being forced to lie on forms under threat.