The studies examined by the authors of this comprehensive effort to review the literature on Kibbutz child rearing are often characterized by widely ranging observations on the same phenomenon. Hence one study claims that Kibbutz children look and behave like Spitz's institutional children, whereas the next study finds that they do not differ from other children. Different child-rearing practices in various Kibbutzim and favorable or unfavorable bias on the part of the researcher contributed to this confusion. Several of the studies cited indicate that the Oedipal conflict loses intensity, as does sibling rivalry, leading to adults who are more group oriented in their strivings, and less inclined toward envy, selfish demands, and intensive, acquisitive drives. The authors note that the only observation all researchers agree on is that there are hardly any marriages between people who have grown up in the same group—almost analogous to a self-created incest taboo.