Blood is thicker: moral spillover effects based on kinship.

Three empirical studies document the intuitive spillover of moral taint from a person who engages in immoral acts to another individual who is related by ties of blood kinship. In Study 1, participants were more likely to recommend that the biological grandchild of a wrongdoer, compared to a non-biological grandchild, help the descendants of his grandfather's victims. In Study 2, participants were more willing to hold two long-lost identical twins in custody for a crime committed by one twin than to hold two perfect look-alikes for a crime committed by one look-alike. Study 3 provides direct evidence that spillover effects based on blood kinship are manifested in an intuitive sense of moral taint.