Birth Order as a Research Variable

Birth order (ordinal position) in the nuclear family has been found to be related to a large number of social and psychological factors. Yet the reasons why are not clear. The literature on birth order reflects considerable theoretical confusion. It appears that researchers often discover the significance of birth order accidentally while engaged in other research. As a result their theorizing tends to be <it>post hoc</it> and to have a disconnected character. There is a need for some system which will aid in the evaluation of existing research findings, and indicate strategic areas for future research. Such a system is introduced, along with some suggestions for research.