Can NT's tell were faking it?
Whether a person is able to fake it or not all depends on the person. Different people with ASD present in different ways, and some people on the spectrum tend to "stand out" more than others, for various reasons.
I will tell you this though...as someone who has met/worked with tons of people with ASDs, most of them can't fake it, even when they think they can. A small minority are able to though, and these are people with mild/borderline presentations of it. As for faking it, I don't recommend it if you have tried and are not able to as it may lead to burnout and exhaustion - none of which you want. There are ways to fit into the larger society without giving up who you are (i.e. surrounding yourself with ASD friends and learning/practicing self-advocacy around NTs).
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Given a “tentative” diagnosis as a child as I needed services at school for what was later correctly discovered to be a major anxiety disorder.
This misdiagnosis caused me significant stress, which lessened upon finding out the truth about myself from my current and past long-term therapists - that I am an anxious and highly sensitive person but do not have an autism spectrum disorder.
My diagnoses - social anxiety disorder and obsessive-compulsive disorder.
I’m no longer involved with the ASD world.