Humans are not born equal. Some are born handicapped or slow to learn, and so they have real challenge with comprehending as quickly as other humans who are born complete or capable.
If you are in the category of humans who are able bodied or capable, you should be sensitive to others who are not. These categories of humans can be observed in classrooms or offices, where a student or employee finds it difficult to comprehend the way others do or they find it difficult to do the “normal” things others find easy.
Be sensitive; help them, if it means going the extra mile repeating yourself over and over so they grasp what you are trying to pass across please do. Do not make a joke out of them, help them. Making a joke out of their frailty or out of their incapability is termed an insult which can be likened to saying they are the cause of the condition they are in. Courtesy and manners which is regarded as common sense demands that capable humans be sensitive to the needs of others who are considered otherwise