For example, my tremor was particularly prominent one afternoon. I went into a shop and the person behind the counter said to me, “are you feeling cold, sir?” Maybe I missed the joke but I decided to be honest, so I said, “no, I’ve got Parkinson’s disease.” A flood of apologises emerged from the person. He wished me a good evening and I said, “I will and I’ll warm up too!” A little bit of self-deprecating humour showed that his supposed superior response to my tremor was totally misplaced. Maybe I taught him something that day.
Another example I’ve encountered is when people equate my physical disability with my level of intelligence and talk…really…slowly…to…me. I happen to have a doctorate (DPhil) in Genetics from Oxford University so I think I understand what you are saying! Such “do…you…under…stand?” people should assume their listener does understand and then, if the need arises, modify the assumption.
A far harsher form of preconception you may encounter is prejudice, which can be defined as judging people (usually negatively) based on physical characteristics or ethnicity or disability. I believe such a judgement is absurd. We were thrown into the world in a particular state when we were born (Heidegger calls this our “thrownness”). Nobody is responsible for their thrownness; we didn’t choose whether we were male or female, had dark or light skin, were susceptible to Parkinson’s or not etc. Therefore judging a person’s thrownness is an empty judgement; the judgement doesn’t apply to the person being judged. Indeed, it’s a judgement about nobody. Judgements should be made on the basis of who people are, not what they are.
I feel sorry for people who live their lives without empathy and self-awareness.