many of the problems with difference scores and profile similarity indices can be avoided by using polynomial regression (edwards, 1994, 2002; edwards & parry, 1993). polynomial regression involves using measures of the person and environment along with relevant higher-order terms (e.g., the squares and product of the person and environment measures) as joint predictors. in addition to avoiding problems with difference scores, polynomial regression allows for the development and testing of hypotheses that go beyond the simple functions captured by difference scores (edwards & shipp, 2007). the polynomial regression equation commonly used in person-environment fit research is as follows: