(PhysOrg.com) -- When you hear the word “planet,” do you automatically think of the word’s literal definition, or of other words, such as “Earth,” “space,” “Mars,” etc.? Especially when used in sentences, words tend to conjure up similar words automatically. Further, human beings’ ability to draw associations and inferences between words may explain why we’re generally able to communicate complex ideas with each other quite clearly using a limited number of words.