Cumulative growth of knowledge? Inconsistency of empirical findings and barriers of scientific communication in birth order research.

Problems of scientific communication are the starting point of the study. To master these problems, the author proposes the development of a methodology of international and interdisciplinary reviews. Problems of international and interdisciplinary searching in sibling and twin research are demonstrated. Catalogs of libraries, the 'Social Sciences Citation Index', bibliographies and indexes, data bases, documentary centres and an expert survey have been used as data sources. Based upon the accumulated data and materials there is given an overview of birth order (sibling position) research: its terminology, research designs, subjects, hypotheses, empirical findings and methodological weaknesses (as criticized in literature). There ist an inflation of terms that are used very inconsistently. The number of studies already published is underestimated by far even by experts and researchers of high scientific reputation. Hypotheses are often contradictory. A great number of researchers and authors of reviews summarizes the partial or whole inconsistency of empirical findings. Many of the new studies repeat the methdological faults already criticized in the early thirties. There are various barriers of scientific communication in birth order (sibling position) research. The process of cumulative growth of knowledge must be called in question in this research area