founded by American social psychology Harold. H. Kelley, with regard to attribution theory, the standard that for an aspect to be a cause of an action, it have to be in existence whenever the action happens, and not be in existence whenever it doesn't happen.
: "In accordance with the covariation principle
, the fact that Kim's episodes of itchiness, sneezing, and watery eyes were only present when she visited homes where cats were present was enough to warrant an allergy
test in suspicion that a cat allergy
would be the cause."