The relationship between birth stress and writing hand posture

BRAIN

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COGNITION

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158-164 (1982)

The Relationship between Birth Stress and Writing Hand Posture ALAN SEARLEMAN St. Lawrence University CLARE P~RAc University of Victoria AND STANLEY COREN University of British Columbia Variations in handwriting posture (inverted versus noninverted) were measured in 1203 individuals for whom birth histories, based upon retrospective maternal reports, were available. A history of birth complications was associated with an increased incidence of inverted handwriting posture. Effects interacted with sex and hand preference; the largest difference in handwriting posture between the birth-stressed and non-birth-stressed groups occurred in left-handers and in males.

Individual differences in the position assumed by the hand during writing have been observed and commented on for many years (see Gould, 1908). As is evident from casual observation, the majority of right-handers use what is called a “straight” or “noninverted” posture in which the hand is positioned below the line of writing and the tip of the pencil or pen is slanted toward the top of the paper. Left-handers, however, display much greater variability in their handwriting postures than do right-handers (Barsley, 1970; Clark, 1957). Although many lefthanders also adopt a noninverted posture, a significant proportion use an “inverted” writing posture that is characterized by the rotation of This research was supported in part by grants from the National Sciences and Engineering Research Council of Canada and the Medical Research Council of Canada. Requests for reprints should be sent to Alan Searleman, Department of Psychology, St. Lawrence University, Canton, NY 13617. 158 0278-2626/82/020158-07$02.00/O Copyright All rights

0 1982 by Academic Press. Inc. of reproduction in any form reserved.

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the hand above the line of writing with the tip of the writing instrument pointing toward the bottom of the paper. Estimates of the incidence of inverted writing posture generally range from 30 to 70% among lefthanders and from 1 to 10% among right-handers (Allen & Wellman, 1980; Coren & Porac, 1979; Levy & Reid, 1978; Peters & Pedersen, 1978; Searleman, Tweedy, & Springer, 1979). Examples of typical noninverted and inverted writing postures are shown in Fig. 1. In the last few years writing hand posture has become a popular, although controversial, research topic (Bradshaw & Taylor, 1979; Coren & Porac, 1979; Levy, 1974; Levy & Reid, 1976, 1978; Peters & Pedersen, 1978; Searleman, 1980; Searleman et al., 1979; Shanon, 1978). The major reason for the recent surge of interest in writing hand posture is due to a suggestion by Levy (1974) that this aspect of writing behavior may predict differences in cerebral organization for language in both left- and right-handers. Based upon the results of tachistoscopic tests, Levy and Reid (1976, 1978) concluded that noninverted writing postures indicate that an individual has linguistic functions primarily localized in the hemisphere contralateral to the writing hand with concomitant contralateral motor control of the writing hand. In contrast, inverted writers purportedly have language and motor control of the writing hand primarily lateralized in the ipsilateral hemisphere. Given the unusual neurological organization postulated for inverted writers, it is not surprising that some researchers have suggested a pathological etiology for this style of handwriting posture. For example, Levy (1974) hypothesized that an ipsilateral relationship between the writing hand and the hemisphere of language and motor control occurs in those rare individuals who have more uncrossed than crossed pyramidal fibers. Since such a neural organization greatly differs from the norm, she suggested that both left- and right-handed inverted writers may have suffered from “a partial failure during some critical stage of embryogenesis for axons to cross the midline of the nervous system” (Levy & Reid, 1978, p. 138). In other words, Levy and Reid suggest that the inverted writing posture results from a partial agenesis of the corpus callosum. Consistent LEFT-HANDED

STRAIGHT

INVERTED

RIGHT-HAWED

INVERTED

FIG. 1. Examples of straight and inverted handwriting postures.

STRAIGHl

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with this hypothesis, Levy and Reid (1978) cite evidence that the performance patterns of subjects with inverted handwriting postures on lateralized verbal and spatial tachistoscopic tests “are very similar to those seen in people with callosal agenesis” (p. 138). McKeever and Hoff (1979) also considered the possibility that the inverted writing posture may arise from a pathological condition. Based on a reaction time (RT) analysis, they proposed that a “disconnection,” or isolation, exists between the left hemisphere’s visual and motor areas in left-handed inverters (this same line of reasoning could be extended to right-handed inverters as well). Also based upon RT to lateralized stimuli, Moscovitch and Smith (1979) have speculated that inverted writers may be characterized as having an anomalous visual or visuomotor organization. It is interesting to note that Allen and Wellman (1980) reported that children with noninverted writing postures had higher reading scores than children who did not. Finally, it has recently been shown that left-handed males with inverted writing postures performed worse than noninverted leftand right-handed males on a neuropsychological test battery (Gregory & Paul, 1980). Recently, there has been renewed interest in the theory that pathological factors can affect preferred handedness. Most studies have concentrated, almost exclusively, on whether or not an individual who had suffered some form of birth stress showed right- versus left-handedness (Bakan, 1971, 1977; Barnes, 1975; Hicks, Evans, & Pellegrini, 1978; Hicks, Pellegrini, & Evans, 1978; Hicks, Pellegrini, Evans, & Moore, 1979; Searleman, Tsao, & Balzer, 1980; Schwartz, 1977; Smart, Jeffery, & Richards, 1980). None of these studies, however, considered handwriting posture as a variable. The present study was conducted to ascertain if potential sources of neurological trauma, such as birth stress or birth complications, are predictive of later handwriting posture. METHOD Through the cooperation of various educational institutions in the Province of British Columbia, Canada, a sample of approximately 4000 families was contacted by mail. Each mother was asked to complete a questionnaire in which she was told to indicate any complications or difficulties encountered in the delivery of each of her children. The specific birth stress factors listed on the questionnaire were: “premature birth,” “prolonged labor,” “breech birth, ” “blue-baby or breathing difficulties,” “low birth weight,” “Caesarean and “Rh incompatibility.” We condelivery, ” “multiple births (i.e., twins or triplets),” sidered this method of assessing the presence of birth complications to be superior to that in which offspring are questioned about the conditions surrounding their own births since individuals can only have second-hand information about the circumstances of their birth and, in some households, such topics may not even be considered appropriate for discussion. Handwriting posture was also assessed for each of the college-aged offspring. Each participant was given a questionnaire that included questions on demographic and medical information. They were also provided with the four prototypical models of handwriting

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posture shown in Fig. 1 and were asked to indicate the posture most like their own. This is the same procedure that has been used by Coren and Porac (1979). The final sample of offspring with complete information about both handwriting posture and birth history consisted of 1203 subjects (556 males and 647 females).

RESULTS

On the basis of the maternal reports each subject was classified as having a stressful birth or a nonstressful birth and the percentage of inverted writers in the two categories was computed. The resulting data are shown in Table 1. We have presented the data, not only for the total sample, but also for males and females separately, since previous reports have shown sex differences both in the effect of birth stress variables on hand use, or at least hand preference (Bakan, 1971; Coren & Porac, 1980; Leviton & Kilty, 1976; Smart et al., 1980) and in the incidence of the various handwriting positions (Allen & Wellman, 1980; Coren & Porac, 1979; Peters & Pedersen, 1978; Searleman et al., 1979). Consistent with other studies, the present findings indicated that the inverted writing posture was much more prevalent among left-handers (46.9%) than among right-handers (7.8%) (x2 = 178.5, p < .OOOl).When one looks at the total sample, irrespective of sex or hand preference, there are more inverted writers among those for whom there are maternal reports of birth stress or birth complications, but this difference is only marginally significant (x2 = 3.04, p < .lO). However, hand preference interacts with the effect of birth stress on writing posture. If one considers the left- and right-handers separately, 69% of the left-handers who experienced some form of birth stress write with an inverted posture, as compared with only 41.2% of those in the normal birth group (x2 = 6.08, TABLE 1 PERCENTAGEOF SUBJECTSWITH INVERTED HANDWRITING POSTUREAS A FUNCTION OF BIRTH STRESS(NUMBER OF CASESIN PARENTHESES)

Total Sample Stress All cases (1203) Males (556) Females

(647) a p < .02 b p < .005 L p < .OOl

15.8

(25% 25.7’ (109) 8.7 (150)

No Stress 11.5 (944) 13.2’ (447) 10.1 (497)

Left-handers Stress 69.0”

No Stress

93.8

41.2” (114) 40.5’

(16)

(42)

(2% 38.5 (13)

41.7

(72)

Right-handers Stress 9.1

(230) 14.0 (93) 5.8 (137)

No Stress 7.5 (830) 10.4 (405) 4.7 (425)

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p < .02). There is no effect of birth complications on handwriting posture for right-handers (x2 = .48, n.s.). Table 1 also shows the hand posture data for males and females separately. In the combined sample of left- and right-handed males, the incidence of hand inversion is significantly higher in males who have experienced any form of birth stress or birth complication (x2 = 9.43, p < .005). Within the male portion of the sample, premature birth, prolonged labor, low birth weight, and Caesarian delivery are each significantly related (p < .05) to an increased likelihood of writing with an inverted hand posture, while breech birth, breathing difficulty, multiple birth, and RH incompatibility are not. For females, however, inversion in handwriting posture does not appear to be related to birth stress conditions, either considered individually, or collapsed across all eight forms of birth complication that we measured. When each sex is considered separately, again, hand preference interacts with the effect of the two variables under consideration. Regardless of the presence of any birth complication, left-handed males were more likely to assume an inverted writing posture than were lefthanded females (55 and 41%, respectively). With the addition of the birth stress variable, one finds that 15 of the 16 (93.8%) left-handed males who had experienced some type of birth complication write with an inverted posture as compared with only 17 of the 42 (40.5%) left-handed males without reported birth stress (x2 = 11.23, p < .OOl). Among the lefthanded females, the incidence of handwriting inversion does not differ significantly for the two birth categories (x2 = .Ol, n.s.). We can clarify the nature of this sex difference by considering this result in another way. The incidence of inverted writing in left-handed males who have suffered birth complications is higher than that of left-handed females in the same category (x2 = 7.83, p < .Ol); however, there is no sex difference in the incidence of inverted writing postures among left-handers with no reported birth stress (x2 = .Ol, n.s.). As can be seen from Table 1, the interaction of sex, birth complication, and the incidence of handwriting inversion is confined to left-handers. DISCUSSION

The present study is the first attempt to determine if writing hand posture is related to any factors that might signal the presence of some form of pathology or trauma in otherwise neurologically intact individuals. Specifically, we have looked at a set of birth complications that might increase the probability that some form of subtle neurological trauma has affected an individual. Our present findings suggest that these birth complications predict variations in the incidence of inverted handwriting posture, particularly in males. This finding is consistent with the position that an inverted writing posture may be a “soft sign” of pa-

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thology or possible neurological trauma (Allen & Wellman, 1980; Gregory & Paul, 1980; Levy & Reid, 1978; McKeever & Hoff, 1979; Moscovitch & Smith, 1979). Handwriting posture, however, cannot be considered in isolation since its incidence varies as a function of sex and hand preference. An inverted hand posture is more prevalent among left-handers than among righthanders, and left-handed males are more likely to use this posture than left-handed females (for a review, see Weber & Bradshaw, 1981). If one can assume that there are multiple causes for hand inversion, then given the high percentage of left-handers who adopt this style it is reasonable to argue that some left-handers are “natural” inverters. This means that their inverted hand posture does not arise from any pathological intervention. However, in some instances, for example, among those who have a history of birth complications, it is likely that a number of individuals who display an inverted handwriting posture do so as a result of the possible neurological effects of some traumatic influence. Our results indicate that the strongest and most consistent relationship between hand inversion and birth stress is for left-handed males. This result is particularly interesting in light of earlier findings associating an increased incidence of left-handedness, particularly in males, with birth stress (Bakan, 1971; Coren & Porac, 1980; Leviton & Kilty, 1976; Smart et al., 1980). It also suggests an important implication for the present findings. The notion of pathological influences in the determination of left-handedness has been a recurrent research theme over the past 70 years (see Porac & Coren, 1981). Satz (1972, 1973) has proposed a model that postulates a certain percentage incidence of pathological left-handedness within populations of left-handers. It is based upon the notion that physiological trauma of some type will cause a switch in the natural handedness patterns from right to left with this being one of the only overt signs of the occurrence of such a trauma. However, when presented with a group of left-handers, it has seldom been possible to ascertain the likelihood that any one person is actually a “pathological” versus “natural” left-hander. The present data suggest that the accuracy of prediction may be increased by considering the handwriting posture variable, especially when considering male left-handers. REFERENCES Allen, M., & Wellman, M. M. 1980. Hand position during writing, cerebral laterality and reading: Age and sex differences. Neuropsychologia, 18, 33-40. Bakan, P. 1971. Handedness and birth order. Nature (London), 229, 195. Bakan, P. 1977. Left handedness and birth order revisited. Neuropsychologia, 15,837-839. Bakan, P., Dibb, G., & Reed, P. 1973. Handedness and birth stress. Neuropsychologia, 11, 363-366.

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