Statistical figures regarding the percentage of left-handers among the population vary greatly. “In the past investigations yielded rather low results, whereas recent enquiries have generally yielded higher percentages (up to 50 %). There are, of course, many reasons for discrepancies, such as the statistical method used (self-assessment, questioning, observation, examination) and the standard applied (strict or vague). Also, it is important to know under which heading the converted left-handers (pseudo-right-hander) were counted (if this can be found out at all afterwards). The last-mentioned point is closely connected with the fact that in certain periods left-handedness was regarded as something inferior, of which parents felt their child must be cured. Later in life the poor creature deliberately suppressed this “blame” and concealed it from others.” (Sattler, J.B. Links und Rechts in der Wahrnehmung des Menschen. Zur Geschichte der Linkshändigkeit, p. 242 [meaning: Left and Right in the perception of human beings. Comments on the history of left-handedness])
Enquiries conducted by the Wilhelmshaven (Northern Germany) labor office yielded a statistical portion of left-handers of 22.2 %, however, converted left-handers could not be recorded accurately. (Sattler, The Converted Left-Hander, page 134 f.). Some scientists believe that the percentages of left-handers and right-handers may be 50 : 50.
See also “Some Thoughts after Confronting the Data Accumulated and the Research Studies” (Sattler, The Converted Left-Hander, page 357 f.). and the article “‘Ambidextrous People’ are Brain-Damaged” taken from the Münchener Medizinische Wochenschrift (reprinted in Sattler, The Converted Left-Hander, pp. 350-356).
Our work showed again and again the significant role that learning processes played in the socialization of a child. Only cooperation with the Interest Group for Left-Handers, the Consulting and Information Center for Left-Handers and Converted Left-Handers and the research project regarding left-handedness and the consequences of converting handedness made it possible to carry out basic research in an empirical way. The benefits of this practical type of research may be outside the range of university work where heterogeneous groups of left-handers are hardly available for the recording of research data. The combination of practical work and theories developed probably yielded in the most comprehensive data collection in the world about left-handers from mixed groups, regarding both number and scientific findings (Sattler, J.B., Links und Rechts in der Wahrnehmung des Menschen. Zur Geschichte der Linkshändigkeit, S. 23).