It is important to treat people with respect and address them in a way that they prefer. While some people may prefer to be addressed by their first name, others may prefer a more formal title such as Mr. or Ms. There is no scientific evidence to suggest that individuals with intellectual disabilities should be addressed differently from individuals without disabilities. In fact, research has shown that people with intellectual disabilities prefer to be addressed in the same way as anyone else, and to be treated with respect and dignity. However, it is important to note that individuals with disabilities are a diverse group, and may have different preferences or needs. Some individuals may prefer to be addressed by their first name as it can make them feel more equal and included, while others may prefer a more formal address to show respect. Therefore, it is always a good idea to ask how someone would like to be addressed and to respect their preferences. In the case of your friend Catherine, it is important to respect her wishes if she has stated that she does not have a preference for how you address her. However, if you are unsure or uncomfortable addressing someone by their first name, it is appropriate to use a more formal title such as Ms. Jones. In summary, it is important to treat everyone with respect and address them in a way that they prefer. While there is no scientific evidence to suggest that individuals with intellectual disabilities should be addressed differently, it is important to recognize that everyone is unique and may have different preferences. It is always appropriate to ask how someone would like to be addressed and to respect their wishes.