“…When research efforts move to the effects of parent -child relationships on child outcomes, there is a new set of methodological challenges, with the need to take account of bidirectional infl uence processes as well as contemporaneous and overtime infl uences in both directions in a transactional and circular causal process (Bornstein, 2006 ;Collins et al, 2000 ;Cook, 2003 ;Kuczynski, 2003a ;Laible & Thompson, 2007 ;O ' Connor, 2002 ;Patterson & Fisher, 2002 ;Pettit & Arsiwalla, 2008 ). There are also conceptual and methodological diffi culties associated with the separation of correlation and causality (Cook, 2003 ;Cowan & Cowan, 2002 ;Howe, Reiss, & Yuh, 2002 ) as well as the specifi cation and separation of the contributions of different environmental effects, including separating the contributions of parent -child relationships from other environmental effects (Bradley, 2002 ).…”