3. Conversion Disorder
Conversion disorder is an unusual psychological disorder that causes people to report symptoms such as blindness and paralysis but without any medical evidence showing an underlying problem. The same can occur with speech.
Someone with a conversion disorder may not speak at all and report that they are not able to, but there is nothing showing a problem in the brain or in the organs of speech.
There are many explanations for the motives of people suffering from this problem. It can be hard to know why someone will have psychological problems, but some may see it as an avoidance behavior in which the mind convinces itself it has a problem to avoid having to confront others or face an uncomfortable issue.
Some may want to be taken care of, and of course, these are mainly subconscious desires, rather than mere playacting.