- Email: [email protected]
Academic discipline, handedness and immune disorders
0028-3932 90 S3.00+0.00 PereamonPresh plc
,~~ur~,ps,~choloyro.Vol. 28,No.3.p~.303-308. 1990. PnntedinGreatBntam
ACADEMIC
DISCIPLINE, HANDEDNESS DISORDERS C.
AND IMMUNE
M. TEMPLE
Developmental Neuropsychology Unit. Department of Psychology. Royal Holloway and Bedford New College. University of London, Egham Hill, Egham, Surrey TW20 OEX, U.K. and The Neuropsychology Unit. University Department of Clinical Neurology. The Radcliffe Infirmary, Woodstock Road. Oxford, OX2 6HE, U.K. (Received 5 September
1989; accepted
25 October
1989)
Abstract-Much debate has surrounded the relative contribution of genetic inheritance and environment to human intelligence. In addition, fetal hormones may influence brain development and affect the qualitative nature of intellectual skills. GE.SCHWINDand BEHAN, Proc. Nutn. Acad. Sci. 79,5097-5100,1982, have suggested that such hormones may also influence both the development of handedness and the development of the immune system. Members of the faculty of the University of Oxford participated in a survey investigating field of study; handedness and immune disorders. Even amongst right-handers, mathematical academics are significantly more susceptible to rare immune disorders and four times likely as verbal academics, to have suffered from a language related problem in childhood. In contrast to previous suggestions. the incidence of left-handedness is not found to be high amongst pure mathematicians but is significantly higher amongst scientists using mathematical applications.
INTRODUCTION MUCH debate has surrounded the relative contribution of genetic inheritance and environment to human intelligence. In addition, fetal brain hormones may influence brain development [4] and affect the future qualitative nature of intellectual skills [S]. In particular, testosterone, a male sex hormone has been implicated in the development of enhanced spatial skills, possibly by slowing the development of the left hemisphere [2,3] of the brain (predisposed to develop linguistic and analytical skills), thereby encouraging the development of the right hemisphere (predisposed to develop non-linguistic skills, e.g. artistic, musical and spatial skills). If an enhanced right hemisphere gains motor dominance, left-handedness may result and where associated left-hemisphere slowing interferes with cell migration, dyslexia and developmental language disorders may result [2, 33. In agreement with this proposal, the incidence of left-handedness has been found to be unusually high amongst dyslexics [9], and among artists [ 111, architects [ 123, mathematics teachers [l] and among mathematically gifted children [6]. In disagreement left-handers have been found to perform poorly on certain spatial tasks [7, S]. More controversially, GESCHWIND [2, 31 has proposed that testosterone impairs the development of the thymus, which in turn influences the development of the immune system. In support, left-handers are reported to be more prone to auto-immune disorders than righthanders [2], although an elevated rate of left-handedness is not found amongst all patients with auto-immune disorders [13]. If the theory is viable, then following the preceding rationale one should, in addition, expect that those with marked spatial talents are more 303
304
C. M. TEMPLE
susceptible to auto-immune disorders than those with marked verbal talents. Further. assuming that not all of the spatially gifted are left-handed this difference should be apparent amongst right-handers as well as left-handers. The results reported here test this hypothesis.
DATABASE The categorization which Geschwind employed in designating immune disorders can be disputed. For example ulcerative colitis is not generally regarded as an immune disorder but Geschwind includes it with celiac disease as immune disorders affecting the gastro-intestinal tract. Some of the other disorders included by Geschwind are really of unknown etiology. GESCHWIND and GALABURDA [3] use the term immune disorder in a specific manner: “We use the term immune disorder to mean atopic disorders (i.e. the allergies, typically of childhood onset). autoimmune disorders and other conditions in which immunity plays a major role in pathogenesis”. It is the latter use of”major role” which may be debated in the medical fraternity. One may wish to reject Geschwindk theory solely because of the ambiguity in his classification ofdisorders. However, given the extensive coverage in neurological journals which the theory has received and the resultant debate which it has engendered. there is interest. in explicitly testing the theory’s predictions. It is with this objective that the faculty of the University of Oxford was selected for study. Usmg a published list from the central administration, all faculty members from seven departments of the University of Oxford were contacted: law. modern languages, mathematics, theoretical physics. theoretical chemistry. engineering and computing. The former two departments were grouped as “verbal academtcs” and the latter five departments as “mathematical academics”. Each faculty member. excepting those on sabbatical leave. was asked to reply to a postal questionnaire and sent a reminder if a reply was not forthcoming. Final response rates for each group were mathematical academics: 96%; verbal academics: 95%. Only 13% of the sample were women. Amongst the verbal academics only 32/167 are women, whilst amongst the mathematical academics only I2 182are women. There is thus a difference in the distribution of academic category of men and women respondents. This is consistent with generally observed trends ofgreater numbers of women in the arts than in the sciences. It is possible that there are biological bases for this difference. However social and cultural factors may also play a significant role. These may be particularly pertinent in a traditional University like Oxford. The percentage of women faculty m the Oxford sample is lower than the overall percentage of women faculty in U.K. universities. In the year of analysis 22% of university faculty in the U.K. were women. Whilst noting the difficulties outlined earlier, each of the disorders mentioned by GEXHWIND and BEHAP;in their 1984 study [2] was selected for inclusion here: allergies; celiac disease; Crohn’s disease; diabetes mellitus: migrame: myasthenia gravis; polymyositis; rheumatoid arthritis; thyroid disorder; ulcerative colitis: dyslexia and stuttering. The most common disorders included in this study were migraine and allergies. In the current study, tt was requested that the nature of any allergies be specified. Hay fever, because of its very high frequency of occurrence. was listed separately. GESCHWIND and BEHAN [2] also included depression and premature greying as controls for any variability in report ofdisease. These were not considered to be options which would encourage response from elderly academics. Glandular fever and appendicitis were included instead. In deciding upon the incidence of the immune disorders. Geschwind included only those for which hospital diagnosis had been obtained. Although this is viable for some of the disorders, e.g. diabetes. whose manifestation is seldom in doubt in any case, the majority of British people suffering from the more common disorders of hay fever, migraine and allergy are unlikely to have consulted a doctor regarding their complaint. Self-report was therefore accepted as a measure ofdisease incidence. Self-report without validation IS not idea1 but there is no reason to suppose that it should differentially create problems in one group of academics in comparison with another. Respondents were asked to mark whether they had ever suffered from any of the listed problems. Familial incidence of these diseases and other questions were also addressed but these data arc not discussed here. The Edinburgh Handedness Inventory (EHI) was included [IO].
RESULTS In total, responses were gathered from 349 subjects. Of these, just under half were verbal academics (n= 167) and just over half were mathematical academics (a= 182). As noted above, GESCHWIND and BEHAN [2] have already reported an elevated incidence of “immune disorders” amongst left-handers. It therefore seemed important to take note of handedness in the analysis. In the main analysis those responders who attained a positive score on the EHI were classified as right-handed and those who attained a negative score were classified as lefthanded. This division resulted in 20 verbal left-handers and 21 mathematical left-handers. Since the Geschwind theory predicts that scores for left-handers will differ from those ofother responders. the left-handed subjects were excluded from the main analysis, which was carried
ACADEMIC
DISCIPLINE,
HANDEDNESS
AND IMMUNE
305
DISORDERS
out on 147 verbal and 161 mathematical right-handed academics. The left-handers data will be discussed subsequently. Those disorders with an incidence of greater than five were analysed separately: hay fever, migraine, allergies, childhood language disorders, and the control disorders glandular fever and appendicitis. The disorders with an incidence of less than five were analysed collectively: celiac disease, Crohn’s disease, rheumatoid arthritis, diabetes and ulcerative colitis. In this sample, there were no reported cases of polymyositis, thyroid disease or myasthenia gravis. The results are reported in Table 1. Z-values were calculated and since the theory predicts a direction for differences, a one-tailed significance level was used. Table 1. Incidence Verbal (n= 147) Predicted
Mathematical (n= 161)
Z-score
Odds ratio
46 28 23 3 2
48 22 36 12 11
0.38 1.43 1.27 2.44* 2.72*
0.9 0.7 1.6 3.9t
13 22
12 19
0.54 0.78
0.8 0.7
5.3t
conditions
Glandular fever Appendicitis *P
Discipline
in right-handers
conditions
Hay fever Migraine Allergies Childhood language Rare disorders Control
of disorders
and disorder:
limit is > 1. right-handers
relative to verbal right-handers.
right-handers
Table 1 indicates that there is no significant difference between the incidence of either hay fever, migraine or allergies in mathematical academics in comparison with verbal academics. In fact, the proportion of verbal academics reporting hay fever shows a higher trend than for mathematical academics, which runs counter to the theory’s predictions. For migraine and allergies the non-significant trend is in the predicted direction. In the overall analysis, a person was rated as either having allergies or not. Thus a person who had three different allergies made the same contribution as a person who had only one. Allergies were further broken down by category, such that a person could score more than once. The non-significant trend of the overall analysis, manifested as a larger proportion of mathematical academics than verbal academics in all but one allergy category. The most common allergy reported was dust (3 verbal, 10 mathematical), followed by animal (3 verbal, 9 mathematical), food (6 verbal, 7 mathematical), penicillin (1 verbal, 3 mathematical), and bee sting (0 verbal, 2 mathematical). Other allergies (10 verbal, 14 mathematical) had an incidence of one or were not specified despite request. In total there were 45 allergy reports from the mathematical academics and 23 allergy reports from verbal academics. It is also evident in Table 1 that mathematical academics were significantly more likely to have suffered from a childhood language difficulty than verbal academics (PcO.01). Four cases of dyslexia and nine of stuttering were reported in the mathematical group and only three of stuttering were reported in the verbal group. The rarer “immune disorders” were also significantly more common amongst mathe-
C. M.
306
TEMPLE
matical academics (P~0.01). Whereas only 1% of verbal academics had the rare immune disorders, 7% of mathematical academics had rare immune disorders. The two control conditions reveal no difference in incidence between verbal and mathematical academics. Odds ratios of the disorders for mathematical to verbal academics were also calculated and are given in Table 1. For childhood language disorders and the rare immune disorders the lower bound of the 95% confidence interval is greater than 1 (1.3 and 1.5, respectively). Some mathematical academics suffer from a greater number of the disorders. Sixteen (10%) of the mathematical academics suffer from more than two of the listed disorders, whereas only three (2%) of the verbal academics suffer from this number (x2 ~8.52, P
and disorders:
left-handers
Although the main analysis only concerned right-handers, data was also collected from left-handers. The incidence of the disorders in the 20 left-handed verbal academics and 21 left-handed mathematical academics is, respectively: hay fever [4, 71; migraine [4, 53; allergies [2, 33; childhood language disorders [l, 31; other predicted conditions [l, 31; glandular fever [3, 31; appendicitis [3, 31. The number of left-handers in the sample is too small for detailed statistical analysis. However, it is notable that in absolute numbers there are more cases of rare immune disorders amongst the 20 left-handed verbal academics than amongst all the 147 right-handed verbal academics: the percentages are 15 and 0.7%, respectively. The incidence of rare immune disorders in mathematical academics does not differ significantly between right and left-handers (7 and 5%). It has been suggested that migraine is more common in left-handers. In this study there was no significant difference between right-handers (16%) and left-handers (22%), though the trend is in the suggested direction. Discipline
and disorder:
strength of handedness
The Edinburgh Handedness Inventory permits a more sensitive classification of handedness than merely the dichotomy of right and left. There is a continuous scale from - 1 (strongly left-handed) to + 1 (strongly right-handed). Thus although there are few lefthanders on the basis of EHI scores of ~0, there are many more subjects who show some reduction in strength of right-handedness in terms of having EHI scores of < + 1. Thus the sample can be divided into strong right-handers (EHI = + 1) of whom there are 201, and those with some left tendency (EHI = < + 1) of whom there are 148. This produces a larger group for analysis by handedness. Results of Z-scores and odds ratios are given in Table 2. The only significant difference is for childhood language disorders. Subjects with EHI = 1 are significantly less likely to have had a childhood language disorder. Handedness
and academic
discipline
Employing the dichotomous classification of handedness used in the main analysis, handedness in the differing academic disciplines was compared. In contrast to previous suggestion, mathematical academics were not found to exhibit a higher incidence of lefthandedness than verbal academics. In both groups 12% of subjects were left-handed. A division of the verbal academics into lawyers and modern linguists showed no further difference with
ACADEMIC
DISCIPLINE,
Table 2. Incidence
HANDEDNESS
of disorders
in relation
EHI=+l (n=201) Predicted
EHI< (n=
IMMUNE
to strength
fl 148)
307
DISORDERS
of handedness
Z-score
No. odds ratio
conditions
Hay fever Migraine Allergies Childhood language Rare disorders Control
AND
60 29 34 6 8
45 30 30 13 9
0 1.46 0.71 3.23* 0.85
1.0 1.5 1.2 3.1t 1.6
13 30
18 17
1.76 1.08
2.0 0.7
conditions
Glandular fever Appendicitis
*p 1. No. odds ratios are for subjects with EHI < + 1 relative
to those with EHI = + 1.
mathematical sciences (i.e. theoretical physics; theoretical chemistry; engineering and computing, n= 105) revealed a distinct contrast. Only 5% of mathematicians were lefthanded but 16% of mathematical scientists were left-handed. This difference is statistically significant (x2 = 5.32, P-z0.05). Since handedness differed between these two groups, a further analysis was conducted to compare their incidence of immune disorder. However, as Table 3 indicates the proportions affected in the two groups are very similar. Table 3. Incidence
of disorders
in mathematical
academics
Pure math. (II = 73) conditions
n
Hay fever Migraine Allergies Childhood language Rare disorders
25 11 17 6 4
0.32 0.14 0.22 0.08 0.05
27 16 22 9 8
0.26 0.15 0.21 0.09 0.08
5 10
0.06 0.13
10 12
0.09 0.11
Predicted
Control
Proportion
Math sci. (n=88) n
Proportion
conditions
Glandular fever Appendicitis
CONCLUSIONS In summary, the results support the predictions derived from the theory of Geschwind, in that rare “immune disorders” and childhood language disorders are more common amongst mathematical academics than amongst verbal academics. However, in contrast, the incidence of hay fever and migraine show no difference between groups. Also consistent with Geschwind’s theory academics who are strongly right-handed are less likely to have had childhood language disorders than other academics. However, there is no similar effect upon
308
C. M. TEMPLE
the incidence of immune disorders. Left-handedness is not more common amongst mathematical academics in general than amongst verbal academics. However, it is more common amongst scientists applying mathematics to other domains than amongst pure mathematians. The common spatial demands of the former and the common analytical demands of the latter may be relevant. Fetal exposure to testosterone may be one factor which effects the development of immune disorders but the results in association with cognitive skill indicate differential effects in relation to the nature of the immune disorder. Further, there is no evidence in this study of a relationship between reduced right-handedness and incidence of immune disorders. Clearly, further factors must be contributing to the pattern of immune disorder. In relation to handedness, there is evidence of an association between reduced right-handedness and developmental language disorders and also an association of left-handedness with cognitive skill in the applied mathematical sciences. However pure mathematicians have the lowest incidence of left-handedness. The handedness results are as explicable in relation to current genetic theory [l] as in relation to the neurohormonal theory but the association of rare immune disorders and academic discipline has no obvious explanation other than that of Geschwind. Acknorvledgements-This research was supported in part by a research award from the Wolfson Foundation. I thank the faculty of the University of Oxford for their cooperation and interest in this study and Dr R. Hiorns of the Department of Biomathematics, University of Oxford for statistical advice.
REFERENCES 1. AG~ETT, M. and KILSHAW, D. Mathematical ability and lateral asymmetry,
Corm 18, 547-568, 1981. 2. GESCHWIND, N. and BEHAX, P. Left-handedness: association with immune disease, migraine and developmental disorder. Proc. mtn. acad. Sci. 79, 5097-5100. 1982. 3. GESCHWIND. N. and GALABURDA, A. Cerebral lateralisation. Biological mechanisms, associations and pathology; a hypothesis and program for research. Archs Neural. 42, 428459. 521-553. 634 654. 1985. 4. Coy, R. B. and MCEWAN, B. S. Sexual Dijjerentiafion ofrhe Brain. MIT Press. Cambridge. MA. 1980. 5. HINES. M. and SHIPLEY, C. Prenatal exposure to diethylstilbestrol (DES) and the development of sexually dimorphic cognitive abilities and cerebral lateralisation. Derl Psych. 20, 81-94. 1984. 6. KOLATA. G. Math genius may have a hormonal basis. Science 222, 1312. 1983. 7. LEVY. .I. Possible basis for theevolution oflateral specialisation ofthe human brain. Nature224,614615, 1969. 8. MILLER. E. Handedness and the pattern of human ability. Br. J. Psycho/. 62, 1 I I 112, 1971. 9. NAIU~, S. Spec$c Dyslexia. Pitman. London, 1972. 10. OLDFIELD, R. C. The assessment and analysis of handedness: The Edinburgh Inventory. Neuropsycholoqia 9. 97-113. 1969. 11. PETERSOX. J. M. Left handedness: differences between student artists and scientists. Percept. Mar. Skills 48. 961-962. 1979. 12. PETERSOK,J. M. and LANSKY, L. M. Left-handedness among architects: some facts and speculations. Percepr. Mot. Skills 38. 547-550. 1974. 13. SALCEDO, .I. R. et crl. The autoimmune disease systemic lupus erythematous is not associated with lefthandeness. Corfex 21, 645-647, 1985.
,~~ur~,ps,~choloyro.Vol. 28,No.3.p~.303-308. 1990. PnntedinGreatBntam
ACADEMIC
DISCIPLINE, HANDEDNESS DISORDERS C.
AND IMMUNE
M. TEMPLE
Developmental Neuropsychology Unit. Department of Psychology. Royal Holloway and Bedford New College. University of London, Egham Hill, Egham, Surrey TW20 OEX, U.K. and The Neuropsychology Unit. University Department of Clinical Neurology. The Radcliffe Infirmary, Woodstock Road. Oxford, OX2 6HE, U.K. (Received 5 September
1989; accepted
25 October
1989)
Abstract-Much debate has surrounded the relative contribution of genetic inheritance and environment to human intelligence. In addition, fetal hormones may influence brain development and affect the qualitative nature of intellectual skills. GE.SCHWINDand BEHAN, Proc. Nutn. Acad. Sci. 79,5097-5100,1982, have suggested that such hormones may also influence both the development of handedness and the development of the immune system. Members of the faculty of the University of Oxford participated in a survey investigating field of study; handedness and immune disorders. Even amongst right-handers, mathematical academics are significantly more susceptible to rare immune disorders and four times likely as verbal academics, to have suffered from a language related problem in childhood. In contrast to previous suggestions. the incidence of left-handedness is not found to be high amongst pure mathematicians but is significantly higher amongst scientists using mathematical applications.
INTRODUCTION MUCH debate has surrounded the relative contribution of genetic inheritance and environment to human intelligence. In addition, fetal brain hormones may influence brain development [4] and affect the future qualitative nature of intellectual skills [S]. In particular, testosterone, a male sex hormone has been implicated in the development of enhanced spatial skills, possibly by slowing the development of the left hemisphere [2,3] of the brain (predisposed to develop linguistic and analytical skills), thereby encouraging the development of the right hemisphere (predisposed to develop non-linguistic skills, e.g. artistic, musical and spatial skills). If an enhanced right hemisphere gains motor dominance, left-handedness may result and where associated left-hemisphere slowing interferes with cell migration, dyslexia and developmental language disorders may result [2, 33. In agreement with this proposal, the incidence of left-handedness has been found to be unusually high amongst dyslexics [9], and among artists [ 111, architects [ 123, mathematics teachers [l] and among mathematically gifted children [6]. In disagreement left-handers have been found to perform poorly on certain spatial tasks [7, S]. More controversially, GESCHWIND [2, 31 has proposed that testosterone impairs the development of the thymus, which in turn influences the development of the immune system. In support, left-handers are reported to be more prone to auto-immune disorders than righthanders [2], although an elevated rate of left-handedness is not found amongst all patients with auto-immune disorders [13]. If the theory is viable, then following the preceding rationale one should, in addition, expect that those with marked spatial talents are more 303
304
C. M. TEMPLE
susceptible to auto-immune disorders than those with marked verbal talents. Further. assuming that not all of the spatially gifted are left-handed this difference should be apparent amongst right-handers as well as left-handers. The results reported here test this hypothesis.
DATABASE The categorization which Geschwind employed in designating immune disorders can be disputed. For example ulcerative colitis is not generally regarded as an immune disorder but Geschwind includes it with celiac disease as immune disorders affecting the gastro-intestinal tract. Some of the other disorders included by Geschwind are really of unknown etiology. GESCHWIND and GALABURDA [3] use the term immune disorder in a specific manner: “We use the term immune disorder to mean atopic disorders (i.e. the allergies, typically of childhood onset). autoimmune disorders and other conditions in which immunity plays a major role in pathogenesis”. It is the latter use of”major role” which may be debated in the medical fraternity. One may wish to reject Geschwindk theory solely because of the ambiguity in his classification ofdisorders. However, given the extensive coverage in neurological journals which the theory has received and the resultant debate which it has engendered. there is interest. in explicitly testing the theory’s predictions. It is with this objective that the faculty of the University of Oxford was selected for study. Usmg a published list from the central administration, all faculty members from seven departments of the University of Oxford were contacted: law. modern languages, mathematics, theoretical physics. theoretical chemistry. engineering and computing. The former two departments were grouped as “verbal academtcs” and the latter five departments as “mathematical academics”. Each faculty member. excepting those on sabbatical leave. was asked to reply to a postal questionnaire and sent a reminder if a reply was not forthcoming. Final response rates for each group were mathematical academics: 96%; verbal academics: 95%. Only 13% of the sample were women. Amongst the verbal academics only 32/167 are women, whilst amongst the mathematical academics only I2 182are women. There is thus a difference in the distribution of academic category of men and women respondents. This is consistent with generally observed trends ofgreater numbers of women in the arts than in the sciences. It is possible that there are biological bases for this difference. However social and cultural factors may also play a significant role. These may be particularly pertinent in a traditional University like Oxford. The percentage of women faculty m the Oxford sample is lower than the overall percentage of women faculty in U.K. universities. In the year of analysis 22% of university faculty in the U.K. were women. Whilst noting the difficulties outlined earlier, each of the disorders mentioned by GEXHWIND and BEHAP;in their 1984 study [2] was selected for inclusion here: allergies; celiac disease; Crohn’s disease; diabetes mellitus: migrame: myasthenia gravis; polymyositis; rheumatoid arthritis; thyroid disorder; ulcerative colitis: dyslexia and stuttering. The most common disorders included in this study were migraine and allergies. In the current study, tt was requested that the nature of any allergies be specified. Hay fever, because of its very high frequency of occurrence. was listed separately. GESCHWIND and BEHAN [2] also included depression and premature greying as controls for any variability in report ofdisease. These were not considered to be options which would encourage response from elderly academics. Glandular fever and appendicitis were included instead. In deciding upon the incidence of the immune disorders. Geschwind included only those for which hospital diagnosis had been obtained. Although this is viable for some of the disorders, e.g. diabetes. whose manifestation is seldom in doubt in any case, the majority of British people suffering from the more common disorders of hay fever, migraine and allergy are unlikely to have consulted a doctor regarding their complaint. Self-report was therefore accepted as a measure ofdisease incidence. Self-report without validation IS not idea1 but there is no reason to suppose that it should differentially create problems in one group of academics in comparison with another. Respondents were asked to mark whether they had ever suffered from any of the listed problems. Familial incidence of these diseases and other questions were also addressed but these data arc not discussed here. The Edinburgh Handedness Inventory (EHI) was included [IO].
RESULTS In total, responses were gathered from 349 subjects. Of these, just under half were verbal academics (n= 167) and just over half were mathematical academics (a= 182). As noted above, GESCHWIND and BEHAN [2] have already reported an elevated incidence of “immune disorders” amongst left-handers. It therefore seemed important to take note of handedness in the analysis. In the main analysis those responders who attained a positive score on the EHI were classified as right-handed and those who attained a negative score were classified as lefthanded. This division resulted in 20 verbal left-handers and 21 mathematical left-handers. Since the Geschwind theory predicts that scores for left-handers will differ from those ofother responders. the left-handed subjects were excluded from the main analysis, which was carried
ACADEMIC
DISCIPLINE,
HANDEDNESS
AND IMMUNE
305
DISORDERS
out on 147 verbal and 161 mathematical right-handed academics. The left-handers data will be discussed subsequently. Those disorders with an incidence of greater than five were analysed separately: hay fever, migraine, allergies, childhood language disorders, and the control disorders glandular fever and appendicitis. The disorders with an incidence of less than five were analysed collectively: celiac disease, Crohn’s disease, rheumatoid arthritis, diabetes and ulcerative colitis. In this sample, there were no reported cases of polymyositis, thyroid disease or myasthenia gravis. The results are reported in Table 1. Z-values were calculated and since the theory predicts a direction for differences, a one-tailed significance level was used. Table 1. Incidence Verbal (n= 147) Predicted
Mathematical (n= 161)
Z-score
Odds ratio
46 28 23 3 2
48 22 36 12 11
0.38 1.43 1.27 2.44* 2.72*
0.9 0.7 1.6 3.9t
13 22
12 19
0.54 0.78
0.8 0.7
5.3t
conditions
Glandular fever Appendicitis *P
Discipline
in right-handers
conditions
Hay fever Migraine Allergies Childhood language Rare disorders Control
of disorders
and disorder:
limit is > 1. right-handers
relative to verbal right-handers.
right-handers
Table 1 indicates that there is no significant difference between the incidence of either hay fever, migraine or allergies in mathematical academics in comparison with verbal academics. In fact, the proportion of verbal academics reporting hay fever shows a higher trend than for mathematical academics, which runs counter to the theory’s predictions. For migraine and allergies the non-significant trend is in the predicted direction. In the overall analysis, a person was rated as either having allergies or not. Thus a person who had three different allergies made the same contribution as a person who had only one. Allergies were further broken down by category, such that a person could score more than once. The non-significant trend of the overall analysis, manifested as a larger proportion of mathematical academics than verbal academics in all but one allergy category. The most common allergy reported was dust (3 verbal, 10 mathematical), followed by animal (3 verbal, 9 mathematical), food (6 verbal, 7 mathematical), penicillin (1 verbal, 3 mathematical), and bee sting (0 verbal, 2 mathematical). Other allergies (10 verbal, 14 mathematical) had an incidence of one or were not specified despite request. In total there were 45 allergy reports from the mathematical academics and 23 allergy reports from verbal academics. It is also evident in Table 1 that mathematical academics were significantly more likely to have suffered from a childhood language difficulty than verbal academics (PcO.01). Four cases of dyslexia and nine of stuttering were reported in the mathematical group and only three of stuttering were reported in the verbal group. The rarer “immune disorders” were also significantly more common amongst mathe-
C. M.
306
TEMPLE
matical academics (P~0.01). Whereas only 1% of verbal academics had the rare immune disorders, 7% of mathematical academics had rare immune disorders. The two control conditions reveal no difference in incidence between verbal and mathematical academics. Odds ratios of the disorders for mathematical to verbal academics were also calculated and are given in Table 1. For childhood language disorders and the rare immune disorders the lower bound of the 95% confidence interval is greater than 1 (1.3 and 1.5, respectively). Some mathematical academics suffer from a greater number of the disorders. Sixteen (10%) of the mathematical academics suffer from more than two of the listed disorders, whereas only three (2%) of the verbal academics suffer from this number (x2 ~8.52, P
and disorders:
left-handers
Although the main analysis only concerned right-handers, data was also collected from left-handers. The incidence of the disorders in the 20 left-handed verbal academics and 21 left-handed mathematical academics is, respectively: hay fever [4, 71; migraine [4, 53; allergies [2, 33; childhood language disorders [l, 31; other predicted conditions [l, 31; glandular fever [3, 31; appendicitis [3, 31. The number of left-handers in the sample is too small for detailed statistical analysis. However, it is notable that in absolute numbers there are more cases of rare immune disorders amongst the 20 left-handed verbal academics than amongst all the 147 right-handed verbal academics: the percentages are 15 and 0.7%, respectively. The incidence of rare immune disorders in mathematical academics does not differ significantly between right and left-handers (7 and 5%). It has been suggested that migraine is more common in left-handers. In this study there was no significant difference between right-handers (16%) and left-handers (22%), though the trend is in the suggested direction. Discipline
and disorder:
strength of handedness
The Edinburgh Handedness Inventory permits a more sensitive classification of handedness than merely the dichotomy of right and left. There is a continuous scale from - 1 (strongly left-handed) to + 1 (strongly right-handed). Thus although there are few lefthanders on the basis of EHI scores of ~0, there are many more subjects who show some reduction in strength of right-handedness in terms of having EHI scores of < + 1. Thus the sample can be divided into strong right-handers (EHI = + 1) of whom there are 201, and those with some left tendency (EHI = < + 1) of whom there are 148. This produces a larger group for analysis by handedness. Results of Z-scores and odds ratios are given in Table 2. The only significant difference is for childhood language disorders. Subjects with EHI = 1 are significantly less likely to have had a childhood language disorder. Handedness
and academic
discipline
Employing the dichotomous classification of handedness used in the main analysis, handedness in the differing academic disciplines was compared. In contrast to previous suggestion, mathematical academics were not found to exhibit a higher incidence of lefthandedness than verbal academics. In both groups 12% of subjects were left-handed. A division of the verbal academics into lawyers and modern linguists showed no further difference with
ACADEMIC
DISCIPLINE,
Table 2. Incidence
HANDEDNESS
of disorders
in relation
EHI=+l (n=201) Predicted
EHI< (n=
IMMUNE
to strength
fl 148)
307
DISORDERS
of handedness
Z-score
No. odds ratio
conditions
Hay fever Migraine Allergies Childhood language Rare disorders Control
AND
60 29 34 6 8
45 30 30 13 9
0 1.46 0.71 3.23* 0.85
1.0 1.5 1.2 3.1t 1.6
13 30
18 17
1.76 1.08
2.0 0.7
conditions
Glandular fever Appendicitis
*p
to those with EHI = + 1.
mathematical sciences (i.e. theoretical physics; theoretical chemistry; engineering and computing, n= 105) revealed a distinct contrast. Only 5% of mathematicians were lefthanded but 16% of mathematical scientists were left-handed. This difference is statistically significant (x2 = 5.32, P-z0.05). Since handedness differed between these two groups, a further analysis was conducted to compare their incidence of immune disorder. However, as Table 3 indicates the proportions affected in the two groups are very similar. Table 3. Incidence
of disorders
in mathematical
academics
Pure math. (II = 73) conditions
n
Hay fever Migraine Allergies Childhood language Rare disorders
25 11 17 6 4
0.32 0.14 0.22 0.08 0.05
27 16 22 9 8
0.26 0.15 0.21 0.09 0.08
5 10
0.06 0.13
10 12
0.09 0.11
Predicted
Control
Proportion
Math sci. (n=88) n
Proportion
conditions
Glandular fever Appendicitis
CONCLUSIONS In summary, the results support the predictions derived from the theory of Geschwind, in that rare “immune disorders” and childhood language disorders are more common amongst mathematical academics than amongst verbal academics. However, in contrast, the incidence of hay fever and migraine show no difference between groups. Also consistent with Geschwind’s theory academics who are strongly right-handed are less likely to have had childhood language disorders than other academics. However, there is no similar effect upon
308
C. M. TEMPLE
the incidence of immune disorders. Left-handedness is not more common amongst mathematical academics in general than amongst verbal academics. However, it is more common amongst scientists applying mathematics to other domains than amongst pure mathematians. The common spatial demands of the former and the common analytical demands of the latter may be relevant. Fetal exposure to testosterone may be one factor which effects the development of immune disorders but the results in association with cognitive skill indicate differential effects in relation to the nature of the immune disorder. Further, there is no evidence in this study of a relationship between reduced right-handedness and incidence of immune disorders. Clearly, further factors must be contributing to the pattern of immune disorder. In relation to handedness, there is evidence of an association between reduced right-handedness and developmental language disorders and also an association of left-handedness with cognitive skill in the applied mathematical sciences. However pure mathematicians have the lowest incidence of left-handedness. The handedness results are as explicable in relation to current genetic theory [l] as in relation to the neurohormonal theory but the association of rare immune disorders and academic discipline has no obvious explanation other than that of Geschwind. Acknorvledgements-This research was supported in part by a research award from the Wolfson Foundation. I thank the faculty of the University of Oxford for their cooperation and interest in this study and Dr R. Hiorns of the Department of Biomathematics, University of Oxford for statistical advice.
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