But then what about the third sense in sensei's above post, interpreting information without words (I'd call it empathy)? Though this relies on sight and sound, it really is a separate, internal sense. Some people are better at it than others, and some people are completely lacking in it (autistic people, for example). This sense develops from experience just as our other senses do, but this it takes stimulation from social interaction, instead of the environment. I think that can be classified as a sixth sense.