Why do some people continually interrupt others while speaking?

Answer 1

Obviously these people are more interested in what they have to say themselves than what anybody else has to say. Watch their faces or body language and you'll probably notice they aren't really paying attention to what the other person is saying because they are too busy thinking about what they want to say.

These people need to learn how to listen to others first then learn when the best time is to add their own bit to the conversation.