Back Cover Blurb
- This book is a critical summary of the world literature (1946-1980) on the influence of birth order on IQ1, personality variables, and psychiatric disorder, followed by empirical data on a representative population.
- It concludes that such influences cannot be generalized and that most results supporting these influences are due to methodological fallacies.
Authors’ Preface (Full Text)
- In part I of this book we have tried to give as complete a survey as possible of studies on the relationship between birth order and socialization, intellectual functioning, and various aspects of personality. The studies considered appeared between 1946 and 1980.
- This survey is imperfect for many reasons, some related to the limitations of the author, others to difficulties inherent in the subject. We will start by enumerating the author's failings.
- Because of the time lag between publication and the appearance of abstracts in scientific periodicals, some recent studies could not be included.
- The research has not been evaluated for its statistical merits or drawbacks, since a thorough study of statistical methods would have overtaxed our time and capabilities. We have limited ourselves to the much decried "hunt for significance," so nonsignificant trends have not been considered.
- We have not systematically reported differences in personality or intellectual endowment related to sex of sib, and those that are reported give an incoherent picture.
- After some attempts, we gave up looking for validity and reliability coefficients of the tests used in the studies. Often they were not reported by the authors, and trying to find data in the pertinent reference works would have protracted our efforts greatly.
- The studies are grouped first according to areas of behavior, then according to constructs, and then according to the methods used. We do not define these constructs and most birth order researchers also fail to do so: they are nothing more than vague common denominators.
- The categorization of a given study under a certain construct is to some degree arbitrary. We have followed the authors' intentions whenever they were reported. Other ways of ordering the studies might lead to different results: The differential interest in task and person found in first- and laterborns, for example, has been listed under the heading "Interest and Values," where the majority of data fail to point out birth order differences. It might as well have been included under "Extra- and Intraversion" to support the opinion of parents that firstborns are more introverted.
- Studies of a very large qualitative range have been included. Thus it was possible to demonstrate that the frequency of birth order results is negatively correlated to the quality of the studies. On the other hand, the enumeration of unsophisticated research makes tedious reading.
- Studies in which birth order differences were discovered accidentally have been included. Since they would not have been published if the results had been negative, they bias the survey to some extent. While collecting material for a survey on IQ2 research we were impressed by the persistent accidental findings of sex differences. Findings that occur repeatedly without being expected are particularly valuable evidence. There are, however, no such trends in accidental birth order results.
- The evaluation of results is open to criticism as well. We have tried to follow a pattern where studies controlling for social variables or using well-matched controls were given more weight than those using unsophisticated methods, and research on sibs within the same family was considered more extensively than either. Since, however, the latter type of research is missing in many areas of behavior, this procedure has not always been possible.
- Other survey writers who evaluate statistical methods, observe trends and interactions, differentiate by sex of sib, and use different evaluation criteria may arrive at different results, particularly in the areas where sib studies are missing. Still, we are convinced that even a survey conducted with better methods will reveal that birth order explains only an extremely small part of variance in the pertinent variables.
- So much for the author's limitations. However, there are flaws and grave imperfections in birth order research itself that become apparent when we list the hypotheses examined here:
- IQ3 is negatively correlated to birth order in that it is higher in firstborns than in laterborns.
- School achievement is negatively correlated to birth order in that it is higher in firstborns than in laterborns.
- Occupational status is negatively correlated to birth order in that it is higher in firstborns than in laterborns.
- Personality varies with birth order; There is a "firstborn personality."
- Risk of mental illness varies with birth order.
- The vagueness of these hypotheses is not accidental. Everybody agrees that birth order differences must arise from differential socialization by the parents. There is, however, no general theory on how this differential socialization actually works, and how it is related to differentials in IQ4, achievement, and personality (Peuckert 1974). Chapter 7 will show the extreme arbitrariness and loose reasoning with wiiich the post hoc theories on socialization and personality are related to differences in variables of birth order that were found with questionable methods. As we will see, Adler is no exception.
- Birth order research seems very simple, since position in a sibship and sibship size are easily defined. The computer is fed some ordinal numbers, and it is then easy to find a plausible post hoc explanation for any significant difference in the related variables. If, for example, lastborn children report more anxiety than other birth ranks, it is because for many years they were the weakest in the family. If firstborns are found to be the most timid, it is because of incoherent treatment by an inexperienced mother. If, on the other hand, middle children show the greatest anxiety, it is because they have been neglected by their parents, being neither the first- nor the lastborn. With some imagination it is even possible to find explanations for greatest anxiety in a second girl of four, and so on, ad infinitum.
- This kind of research is a sheer waste of time and money. If birth order research is to be continued, coherent theories must be formulated and explicit hypotheses derived. The hypotheses must be tested, taking into account the methodological fallacies that will be described in Chap. 1. We have tried to do this in part II. Most of the hypotheses we examined have been refuted.
- Our book aims to put an end to the above-described inadequate kind of research. Perhaps some researchers will take up birth order differences in intellectual development and/or personality afresh; but it may be that having read this survey they will refrain from doing so under the impression that, even with unobjectionable methods, only very modest results can be expected.
Text Colour Conventions (see disclaimer)
- Blue: Text by me; © Theo Todman, 2021
- Mauve: Text by correspondent(s) or other author(s); © the author(s)