In terms of etiquette and social norms, it is generally appropriate to address a person by their last name with a title such as Mr., Ms., or Mrs. However, this custom varies based on cultural background, personal preferences, and the nature of the relationship between the two individuals. In the scenario presented, the speaker has a friend named Catherine Jones and they commonly address her by her first name. It is important to note that the speaker has an intellectual disability and is concerned about whether using only the first name is appropriate. While some may argue that using a title such as Ms. Jones is necessary to show respect to the individual, it ultimately depends on the relationship and communication between the speaker and the individual in question. If the individual being addressed has specifically stated that they do not care how they are addressed, then using their first name is perfectly acceptable. Additionally, it is important to consider the social norms and expectations of the community or culture in which they are interacting. If addressing individuals by their first name is common, then it may not be necessary to use a title every time. Respecting differences, as mentioned by the speaker, is an important aspect of social interactions. Each individual has a unique set of preferences and communication styles, which should be honored and respected. There is no universal correct way to address a person, and it is important to take into account their personal preferences, situation, and cultural background. To conclude, the speaker can continue to use Catherine's first name, as long as they have discussed it with her and she has confirmed that it is acceptable. Addressing individuals by their first name is becoming increasingly common, especially in informal settings, and it is not necessarily disrespectful. Ultimately, effective communication and respecting personal preferences are key to successful social interactions.