a2 Department of Clinical, Biological, and Differential Psychology, School of Psychology, University of Vienna, A-1010 Vienna, Austria. email@example.com
a3 Department of Psychology, St. Mary's University, Halifax, Nova Scotia, B3H 3C3, Canada. firstname.lastname@example.org
Integration of different lines of research concerning grandparental investment appears to be both promising and necessary. However, it must stop short when confronted with incommensurate arguments and hypotheses, either within or between disciplines. Further, some hypotheses have less plausibility and veridicality than others. This point is illustrated with results that conflict previous conclusions from evolutionary psychology about differential grandparental investment.