Thom, who has a terrific stage voice and manner, leaves no question as to the theater’s loss in limiting her range of roles. Her performance of Mouth is as terrifying as any and yet, in its vulnerability to neurological static, more human than most. You understand how the very lonely woman Beckett wrote could have wound up that way.

I would hate to have missed this performance, and yet it might easily never have happened. Feeling for too many years that theater was “not a space I could occupy,” Thom said in a post-show discussion, she almost gave up on it. (As a performer, she would have been deemed uncastable; as an audience member, disruptive.) Only in finding “Not I,” produced by Battersea Arts Center along with Thom’s organization Touretteshero, did she find a way to “occupy the only seat in the house I couldn’t be asked to leave.”

That’s admirable, sure. But the key is that once seated there, Thom uses her position to explore something beyond just Tourette’s. Shining a light into Beckett from a different angle, she illuminates a different part of the rest of us as well.

A similar idea animates “The Shadow Whose Prey the Hunter Becomes,” running at the Public’s Manhattan mother ship through Jan. 19. At first, the play seems to be merely a witty piece of documentary theater, recreating a real-life meeting at which the performers (Michael Chan, Simon Laherty, Sarah Mainwaring and Scott Price) bicker over their parliamentary roles and chafe about definitions. Some, we learn, are comfortable calling themselves disabled but others are not; Price thinks of himself as someone who, in addition to a thick Australian accent, has an “autistic dialect.”

The equating of accent and autism, one of which we usually consider trivial and the other hugely portentous, was eye-opening for me. If Price’s autism is a dialect, surely my own neurological makeup is one, too. What are all our habits of thinking, our charming neuroses, our nature and character, if seen uncharitably, but undiagnosed defects? What is so typical about neurotypical minds?