Johanna Barbara Sattler
In hypotheses about the origin and development of handedness the term “ambidextrous” is defined very differently and often only applied to the subjects assessing themselves. In test examinations alleged ambidextrous persons proved to be either converted left-handers or persons whose results were highly incoherent or even contradictory. Systematic investigations of the second group of subjects always revealed perinatal cerebral disturbances. This paper discusses the thesis that insufficient oxygen supply to the brain in the perinatal period of life mainly affects the function of the dominant cerebral hemisphere that is responsible for the congenital handedness. This results, phenomenally, in temporary change in the use of hands, so that the person is often wrongly diagnosed as being ambidextrous.
The Consulting and Information Center for Left-Handers and converted Left-Handers originated in 1985 from a common research project of scientists from the University of Cologne and the Organization for Neutral Research and Science, the ONRS, a non-profit public service organization. The primary focus of the Center is first and foremost, the prevention of converting left-handed children to their right hand. With this task in mind, persons seeking advice and help at the Center are provided with extensive high-tech testing methods including computerized devices to determine handedness which along with other technological equipment were made available to the Consulting Center by the University of Cologne. Whenever possible data is also collected from the entire immediate family as well as other relatives.
To date, results have shown values of a clearly distinguishable nature for a large compact group of left-handers and right-handers. Before testing, the majority of the converted left-handers presented themselves behaviorally either as unquestionable right-handers who could also use their left hands or as being ambidextrous! Such findings have often come from the frequently used but highly unreliable testing method of self-appraisal of one’s own handedness. This self-appraisal is dependent upon the questions raised, sociological and psychological processes as well as the chance knowledge of the subject. Given this subjectivity and the fact that ambidexterity is viewed as being a valuable attribute, statistical results based upon such methods of data collection are practically unusable (, chapter 2).
However, a small group, seemingly made of a continuum or bridge between left-handers and right-handers did turn up. In reference to this intermediary group, two research questions were explored: (1) Does this intermediary group actually comprise a set of ambidextrous individuals, who are so often mentioned in some of the literature?; and (2) Is handedness gradable and measurable in terms of percentages or degrees which stretch from one extreme to the other?
The analysis of the data raised confirmed neither one of these theses. The intermediary group proved too diffuse to be called ambidextrous. A balanced mean was practically never achieved among the otherwise largely correlating individual tests. Only when one takes the perspective that twofactors could be determinant, did the problematic of cerebral hemispheric dominance and the manifestation of “phenomenally graded” handedness become both plausible and logical.
Consequences of Converting Handedness. The handedness of a human being is an expression of an inborn, innate lateralization of the cerebral hemispheres where one side dominates. In the neural system, the tracts are “crossed”. Thus, a dominant right cerebral hemisphere results in a dominant left hand and a dominance of the left cerebral hemisphere is responsible for right-handedness .
Converting handedness, whether it be from a dominant left hand to a non-dominant right or the reverse, (especially during writing) does not result in a change in cerebral dominance but rather a multifaceted cerebral disturbance or damage. This functional cerebral damage (dysfunction, blockage, and inhibition of brain functioning) can then be manifest in the following primary disorders: disturbances in memory for all three areas of information processing (encoding, storage, and recall); difficulty in concentration (early fatigue); difficulty in reading and spelling (legasthenic problems); spatial disorientation (e.g. confusion of left and right); speech problems ranging from stammering to stuttering; fine motor disturbances evident in writing and other activities requiring precision.
The primary consequences can then go on and transform into secondary consequences: feelings of inferiority; shyness; introversion; overcompensation; defiance to belligerence; braggadocio; provocative behavior; bed-wetting; nail-biting; emotional problems that can last into adulthood with neurotic and/or psychosomatic symptomology; and personality disturbances [ 3,4,7,8,9,11,14] .
Cerebral disturbances. The search for the second factor began with the search for the commonalities in the medical histories of the persons in the small heterogeneous “intermediary group”. Very quickly, problems during pregnancy and birth, as well as difficulties in early childhood were found. In addition, symptoms were found that are often subsumed today under the following terms: MCD – Minimal Cerebral Dysfunction; POS – early childhood Psycho-Organic Syndrome, the foremost term used in Switzerland today; early childhood brain damage; and early childhood exogenous psychological syndrome. (Many of these disturbances are listed in the catalogue, International Classification of Diseases [ 5] . See Chapter V “Diseases in Childhood and Youth”). In children it has been observed that frequently partial disturbances in performance are related to perinatal brain damage (from the sixth month of pregnancy to the end of the first year) and a temporary interruption of the oxygen supply to the brain [ 1] .
These cerebral disorders are in part very similar and are, in fact, often identical to the consequences of converting handedness. Without the necessary knowledge, it is almost impossible to distinguish one from another. The problematic lies in the differential diagnostic method.
Consequences of Oxygen Deprivation in Humans. In the human body, the brain is the most dependent upon oxygen and is consequently also the most affected by a decrease or deprivation of oxygen.
Many examples of this phenomenon have become known in medicine. Such cases involve a temporary shortage of oxygen during birth (MCD). The effects of this deprivation may last throughout the school years and may affect personality development. Such medical cases also encompass a variety of cerebral disturbances (see also the corresponding ICD Numbers) and accidents during any stage of life where even a short-term interruption in the oxygen supply can lead to serious cerebral damage. Even a relatively short interruption in the flow of oxygen can lead to massive disturbances.
A dramatic example of this fact comes from our practice at the Consulting Center. The course of a process of retardation could be readily observed in Andreas, a young man who was violently torn from his normal course of development due to a sports accident. Struck in the throat by a ball and then lain incorrectly, the boy suffered an interruption in the supply of blood to his head. According to the physiological and neurological medical reports available, Andreas suffered hypoxic cerebral damage due to cardiac arrest and circulatory failure. The result: Andreas abruptly changed from a highly talented 18 year old high school student bound for college to a completely emotionally disturbed worker with very limited coordination ability who landed in a workshop for the mentally impaired.
The Effects of Oxygen Deprivation upon Cerebral Dominance and Handedness. Lateralization of the brain entails to the functional specialization of the individual hemispheres and dominance of one of the two hemispheres. This lateralization is genetically based and is hereditarily determined. Moreover, based on the conclusions of biological comparisons with other mammals, it is probable that the lateralization represents the latest stage of development in the human brain. Possibly, this function is accordingly also the most vulnerable and sensitive and has
the potential of being massively disturbed.
For these reasons, somatic or physiological factors can result in brain injuries that are mostly short-term in nature which can also then disturb the dominance in the cerebral hemispheres with differing degrees of effect. Such disturbances may manifest themselves in unstable and variable handedness. This manifestation then precipitates the label “ambidexterity” or an incorrect evaluation of handedness.
The dominance of one half of the brain logically also entails more functional operations in this hemisphere for the processing of impulses and the subsequent activation of contra-laterally positioned parts of the body. The dominant hemisphere takes on a greater number of tasks and consequently requires a greater supply of oxygen. If a shortage of oxygen occurs, it is logical that the dominant cerebral hemisphere would not only be the first but also the most significantly affected.
In the previously described case, the subject Andreas was thoroughly tested at the Consulting Center. It was determined through the use of pictures and pattern tests, that Andreas, driven by the right side of his brain (which was the non-dominant side in his case), constructed more complete and closed patterns (this finding is corroborated by the work of Springer and Deutsch who debate extensively the numerous articles published on the related research results of Sperry, Gazzaniga, Gschwind, et al. ). Before the accident, however, he was clearly right-handed. The most plausible explanation is that the dominant left side of his brain was more greatly affected by the shortage of oxygen and, for this reason, the non-dominant side of his brain took over when recreating the compulsory patterns.
It is a neuro-physiological fact that the region of the brain that participates in the processing of certain pieces of information has an elevated blood flow and consequently a greater oxygen requirement. This fact is taken advantage of in Positronic Emissions Tomography or “PET”. PET involves the injection of radioactively labeled water which is then transported along with the blood into the brain. Elevated levels of blood circulation in the active areas of the brain are then measured with the use of a detector placed around the head.
In reference to the issue of handedness, this means that children who suffered oxygen deprivation during the perinatal period also suffer more serious injuries in the dominant side of the brain than in the non-dominant side. This then has an effect upon the phenomenological development of handedness manifested and explains why many of these children vary the use of their hands until they reach school age. Only much later will they settle upon using one hand. In the literature and in experimental testing, these children are often labeled “ambidextrous”. And in regard to their school performance, they are frequently labeled “problem cases”.
This also explains why during the period of time in which the cerebral hemispheric dominance normally begins to manifest itself through hand preference, the correct handedness of many children cannot be reliably determined and how then the correct handedness of these children may be unintentionally converted. Based on the experiences of real case studies, children, who have suffered cerebral damage and who have difficulty in school, may experience a gradual reduction in the resulting impairments until the age of puberty is reached. At this time, the early disabilities are compensated for, often disappear completely, or only surface in the form of unexpectedly flipping letters or numbers when writing quickly. During the development of the brain, the disturbances are most probably compensated for through the functioning of other regions of the brain. This compensation has been witnessed after brain surgery. Thus, a purely somatic process is at work. If, however, during this period the inborn handedness is converted, a psychosomaticprocess, a new, additional trauma to the brain occurs. The result of this trauma is manifest in the same way as the physiological disturbance. However, a disproportionate aggravation of the cerebral dysfunctions occurs.
The personal style for coping with the negative consequences and the resulting personality characteristics are dependent upon the nature of the cerebral disturbances. The combination of the support that the individual receives, that person’s strength of will, tenacity, and especially the so-called “Demosthenes-Effect” (Demosthenes-Effect = an overcompensation of a defect or disability which the person is actively aware of. The effect is named after the Greek orator Demosthenes, who was a former stutterer, placed pebbles into his mouth, spoke aloud, trying to drown out the sounds of the sea, until he had finally manage to overcome his previous speech defect) all play an important role. However, the secondary consequences must always be taken into account. The entire picture of disruption can present a sociological configuration for the entire life-span ([ 16] , Chapter 6.2.1).
Naturally, people who never had their handedness converted or who have never been confronted with a somatic brain injury, develop normally. They all have abilities that correspond to the particular lateralization (i.e. the various functions and abilities that correspond to the particular dominant hemisphere [ 6] ). In addition, there are also the talents the individual has and supports the person may receive. As substantiation for the hypotheses put forth here, 300 cases were chosen randomly out of a total subject pool of 2119. The data analyzed support the hypotheses given [ 17] .
When the brain is deprived of oxygen, the dominant cerebral hemisphere is the most significantly damaged for the very reason that it must fulfill more of the brain’s functions and has consequently a greater oxygen requirement. Through oxygen deprivation, disturbances in the naturally dominant cerebral hemisphere are manifest. This means that a child who suffered such damages switches back and forth between using the left and right hand and may at first even perform worse with the dominant hand than with the non-dominant hand while, for example, drawing or writing. The outside influence of the socio-cultural environment, namely the “right-handed culture”, may have life-long, detrimental effects on left-handed children, the overwhelming majority of whom are exposed to environmental attitudes like “Left-handedness is an aberration” or “We live in a world that is set-up for right-handers”. The process of converting the child can then have massive detrimental effects that can extend across the child’s entire life. Thus, frequently, the natural development is interrupted. Namely, the process of cerebral compensation, favoring the hand that is not dominant, is negatively affected. This is especially evident in writing. In this way, these children then suffer new damage. The healing processes initiated (namely, compensation by other regions of the brain) are then disrupted once again and the slowly convalescing dominant cerebral hemisphere is damaged anew.
The degree of damage suffered ranging from the least to the most severe case is listed below:
- Disruption of the cerebral functioning especially due to the oxygen deprivation.
- Converting handedness which in turn results in a disruption of brain functioning.
- Damage resulting from the original cerebral dysfunction as well as the additional converting of handedness.
Ambidexterity is therefore neither a goal to aspire to nor is it a gift from God. Instead, it is first and foremost the mark of brain damage.
It is the task of the future to then give special attention to, support and protect those seemingly ambidextrous children who often for some time are unable to determine themselves which hand to predominantly use. This difficulty is a signal of functional cerebral damage; namely, the injury of the dominant cerebral hemisphere. Currently, this issue has not yet been given enough emphasis within either medicine or pedagogy. Indeed, the problem is not yet understood. Our picture of the world, our patterns, and dogmas [ 15] have up to now, scarcely allowed us to open the doors that would permit us to correctly classify or comprehend this phenomenon. However, with all of these thoughts and considerations in mind, several intervening factors should also not be forgotten. The effect of such modifying factors as various talents, differing temperaments, along with the individual influences of the parental home, sibling-constellations, and school.
Conclusions for Practical Application
On the basis of extensive diagnostic testing, the overwhelming majority of people may be clearly categorized as either right- or left-handers. The hypothesis presented and supported here is that ambidexterity which is frequently viewed as a positive attribute, is in fact either (1) the result of the converting of a left-hander (a functional brain damage); or (2) the result of perinatal cerebral damage in the dominant cerebral hemisphere.
This work is a summary of the research report from Oct. 12, 1992, “Ergebnisse der Praxis und Hypothesen über den Zusammenhang zerebraler Störungen des Kindesalters und Händigkeit” (Results from the Field Research and Hypotheses on the Connection Between Cerebral Damage in Childhood and Handedness”) by Dr. Johanna Barbara Sattler, The Consulting and Information Center for Left-Handers and Converted Left-Handers, Munich-Germany [ 17] .
Key Words: Handedness – “Ambidexter” – Cerebral Demage
Schlüsselwörte: Händigkeit – Beidhändigkeit – zerebrale Schädigung
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© Copyright: Dr. Johanna Barbara Sattler
Consulting and Information Center for Left-handers and Converted Left-handers
(Erste deutsche Beratungs- und Informationsstelle für Linkshänder und umgeschulte Linkshänder)
Sendlinger Str. 17, D – 80331 Munich (München), Germany / Europe, Tel./ Fax: +49 / 89 / 26 86 14
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