I know from personal experience that a brain disfunction can manifest as a person being unable to understand the meaning of “not,” that the negative is the opposite of the positive. For example, an injunction such as “do not step off the curb in front of that car,” registers as simply “step off the curb.” The result can be disasterous.
But what if the missed word is actually “do?” I am thinking of that because poor Donald is constantly referencing things he has DONE, when, in fact, he does nothing. His niece, Mary, says he has always been institutionalized. Does she mean that everything has always been done for him? Because he does not know how to do anything? He can barely walk down an incline on his own.