It would be more useful to identify link types - By color & +/- sign
The map, as a whole, would be more useful if the links (as an indicator of relatedness) were to show what *form* of relationship. For example, it is a very different thing to say that "crime is related to punishment" than it is to say "crime should be punished" or to say, "increases in the level of crime lead to increased levels of punishment)