Library of Excerpts

Birth Order, Maturation Rates and Handedness

[abstract] "Pregnancy and delivery complications as indicated in medical records and maternal reports for 23 high-functioning autistic females and 23 high-functioning males of similar IQ and age were compared with those of 54 of their normally developing siblings. Autistic subjects of both sexes had higher non-optimality scores than their siblings. Much of this difference was accounted for by a higher incidence of firstborns and fourth- or later-borns in the autistic group. Of factors found in previous research with mentally handicapped, autistic samples, only estimated weeks of gestation greater than 42 occurred more often in autistic subjects than siblings. The only sex difference specific to the autistic group was that autistic males came from larger families than females. These data provide slight support for the contribution of nonspecific pre- and perinatal factors to other etiological bases of autism. It is proposed that pre- and perinatal factors may play less of a role in autism in high-functioning individuals than suggested in studies of autism associated with severe retardation." (Lord C, Mulloy C, Wendelboe M, Schopler E (1991) Pre- and perinatal factors in high-functioning females and males with autism. J Autism Dev Disord 21(2):197-209)

“Reviews the literature examining the relationship between birth order, birth stress, and lateral preferences in nonclinical samples, with special emphasis on reports since 1971. The review found no evidence to relate birth order position to deviations from right-sidedness for either sex. More direct measures of birth stress indicated that deviations from right-handedness (particularly for male subjects), and also right-eyedness, were statistically related to specific birth stressors. It should be stressed, however, that all the relationships, including the significant ones, were very weak, accounting for less than 1% of the variance. When statistical significance was achieved, it was largely due to the huge sample sizes used in the meta-analyses. Methological and theoretical problems exist in the current literature, and we offer some suggestions to resolve them.” (Searleman A, Porac C, Coren S (1989) Relationship between birth order, birth stress, and lateral preferences: a critical review. Psychol Bull 105 (3):397)

"Females with high T give birth to females with high T and males with low T. Males with low T tend to sire progeny characterized by females with high T and males with low T. Older females, females with higher T, have more left-handed progeny, not because of increased birth trauma, but because females program the developmental rate of their progeny based on the sex of their progeny and the mother's T level (Geschwind & Galaburda, 1987). Low T females and high T males create low T females and high T males. The older the mother the higher her T levels and the more developmentally delayed her male progeny, the more developmentally accelerated her female progeny." (Lehman A & Bernsten M (1999) Evolution and the Structure of Health and Disease web link)

“In a case-control study of testis cancer 259 cases with testicular cancer, 238 controls treated at radiotherapy centres and 251 non-radiotherapy hospital in-patient controls were interviewed about some possible prenatal and familial risk factors for the tumour. For firstborn men, the risk of testis cancer increased significantly according to maternal age at the subject's birth, and this effect was most marked for seminoma. The association with maternal age was not apparent for cases other than firstborn. The risk of testis cancer was also significantly raised for men from small sibships and of early birth order. These results accord with the theory that raised maternal levels of available oestrogen during the early part of pregnancy are aetiological for testicular cancer in the son, although other explanations are possible; there is evidence that seminoma risk may particularly be affected.” (Swerdlow AJ, Huttly SR, Smith P G(1987) Prenatal and familial associations of testicular cancer. Br J Cancer 55 (5):571)


"In 20 out of 27 separate samples of alcoholic men, representing geographically diverse areas of Western European culture, there were more lastborn than firstborn cases from families of 2 or more children. The same was found in 6 samples of women alcoholics, although the trend was less consistent than in the men." (Blane H, Barry H III (1973) Birth order and alcoholism: A review. Q. J. Studies on Alcohol 34: 837)

"Lastborn alcoholics outnumbered firstborn in 20 of the 27 samples." (Blane H, Barry H III (1973) Birth order and alcoholism: A review. Q. J. Studies on Alcohol 34: 840)

"Data are needed from more and larger samples of women alcoholics, but the information available indicated that overrepresentation of lastborn cases characterizes most samples of men but not women alcoholics." (Blane H, Barry H III (1973) Birth order and alcoholism: A review. Q. J. Studies on Alcohol 34: 841)

[citations removed] "The specific overrepresentation of lastborn cases, especially in large families, has been found also in some other categories of psychiatric patients. These include schizophrenics, nonschizophrenics psychiatric patients as pointed out by Barry and Barry, the homosexual men as pointed out by Davis. The existence of this pattern in all types of psychiatric patients would be evidence of a population birth-rate bias or other artifact. ... Obsessive-compulsive behavior and hypertension have been reported to be associated with first-born position, as has outstanding achievement. ... An interesting but isolated report by Martensen-Larsen was that whereas male alcoholics were preponderantly later born, their parents and wives were preponderantly first born." (Blane H, Barry H III (1973) Birth order and alcoholism: A review. Q. J. Studies on Alcohol 34: 845-7)

[citations removed] [Vermont 1981-1985] "In our sample of alcoholic men: (a) significantly more LH men were first-born; (b) significantly more men either LH or having a LH first-degree relative had an alcoholic father; (c) the RH men showed a slightly increased frequency of having an alcoholic mother or maternal grandfather; and (d) the RH men, particularly those having a maternal family history of alcoholism, were born more frequently than expected in summer and fall. This report indicates that the LH individuals in our sample were hospitalized more frequently than expected during October, a finding possibly related to Irwin's hypothesis. ... Twenty-four percent (10/42) of the LH individuals (seven of 32 men and three of 10 women) were hospitalized during October, vs 7% (19/278) of the RH individuals. .... The RH admissions were distributed equally throughout the year (7-10% per month; expected value, 8%). Stated another way, 13% of the sample were LH and so the expected percent of LH admissions during any month is also 13%. During October, however, 34% (10/29) of the admissions were LH, vs 11% (32/291) during the rest of the year (P<0.005, as above). The only other month with an excess of LH admissions was May, during which 23% (6/26) of the admissions were LH." London, WP (1986) Month of hospitalization of left-handed substance abusers. Neuropsychologia 24: 455)

"Table 1 shows the relationship between handedness and the two categories of birth order--high risk (first and fourth or later birth) and low risk (second or third births). For the whole group there are significantly more (P=0.05) left handed persons in the low risk category, the exact opposite of the previous findings. If the results of these and previous investigations are combined, there are almost equal numbers in both risk categories for both right and left handed series. These results strongly suggest that the apparent effect of birth order on handedness is simply a sampling error." (Hubbard, JI (1971) Handedness not a function of birth order. Nature 232: 276)

"in a large representative sample of young men [7380 in France], no clearly significant relationship between handedness and birth order or season of birth was found; the trend was opposite to that claimed be Bakan (1971) and Badian (1983). (Dellatolas, G., Curt, F., Lellouch, J. (1991) Birth order and month of birth are not related with handedness in a sample of 9370 young men. Cortex 27 (1): 139)

"The use of four birth order groupings provides us with three findings not available previously. First, the risk of left handedness is relatively high in both first and fourth and higher birth order boys. Second, the risk of left-handedness tends to be highest in the highest birth orders." (Leviton, A. & Kilty, T. (1976) Letter: Birth order and left-handedness. Arch Neurol 33 (9): 664)

Chart describes following birth order-handedness relationships using 488 sixth-graders: Birth order percentage of left-handed writers: Girls - position 1 (8.7%, position 2 and 3 (10.2%), position 4 & 5 (9.5%, birth position 6 and over (17.9%). Boys - position 1 (10.9%), position 2 & 3 (5.0%), position 4 & 5 (13.6%), positions 6 and over (18.5%)" (Leviton, A. & Kilty, T. (1976) Letter: Birth order and left-handedness. Arch Neurol 33 (9): 664)

"There were not only no significant maternal age or birth order effects for girls, but the female birth order trend was the reverse of that observed for boys. That is, nonright-handedness among girls was slightly higher for birth orders two and three, than for one and four-or-later. ... Leviton dn Kilty (1979a) reported a peak in left-handedness for girls born in or immediately adjacent to November, but no appreciable cyclic variation in season of birth for left-handed boys." (Badian, N.A. (1983) Birth order, maternal age, season of birth, and handedness. Cortex 19 (4): 460)

"The handedness of 942 subjects (305 tiertiary students, 591 of their siblings and 46 of their children) was ascertained by a 14-1tem questionaire. The mothers of the subjects supplied information about maternal age at birth, birth wieght and the presence or absence of twelve conditions likely to be associated with birth stress for each subject. No increase in left handedness was found among fourth or late born childen. A significant decrease occured in first-borns of both sexes, although these had more stessful births than the other subjects. No relationship between maternal age, birth weight or reported birth stress and left handedness was found." Tan, L.E. & Nettleton, N.C (1980) Left handedness, birth order and birth stress. Cortex 16 (3): 373)

"Nonright-handedness occurred among 19.9 percent of the 282 boys in birth orders one and fourth-or-later, compared with 11.3 percent of the 266 second- or third-born boys. The U-shaped curve was not observed for the girls, and there was no significant difference between the two groups (Chi square = 0.85, n.s.). There was, in fact, a slightly higher percentage of nonright-handed girls for positions two and three (15.98 percent) than for positions one and fourth-or-later (13.2 percent.) (Badian, N.A. (1983) Birth order, maternal age, season of birth, and handedness. Cortex 19 (4): 453)

"Dr. Singh....found that menarche is experienced later, on the average, by girls from large families than by those from small families. ... The results are those of Roberts and Dant who suggested that girls born later in sibships mature earlier than those born earlier in the same sibships." (James, W.H. (1973) Age of menarche, family size, and birth order. American Journal Obstetrics Gynecology 116 (2): 292)

"Of the 136 men, 24 (17.6%) were left-handed. This incidence is significantly higher (p<.001) than that of the approximately 10% of men in the general population who are left-handed (Karpinos and Grossman, 1953; Oldfield, 1971). Of the 48 women, only 8% (N=4) were left-handed. Left-handedness was significantly more frequent in alcohol-abusing men with alcoholic fathers (12/44 = 27%) than in those with nonalcoholic fathers (8/74 = 11%; p=.01) and in first-born (11/31 = 35%) than in nonfirst-born men (9/78 = 12%; p<.004). Of the right-handed men and women, 45% (34/76) had a first-degree relative who was left-handed. Additionally, of the right-handed men with alcoholic fathers, 66% (12/18) had a first-degree relative who was left-handed, compared to the 34% (13/38) of the right-handed men with nonalcoholic fathers (p<.03). ... Of the left-handed men, 60% (17/28) --- vs. 30% (32/107) of the right-handed men --- had an alcoholic father (p<.003). (The frequency of maternal alcoholism in the sample was substantially lower, approximately 13%, and appeared unrelated to handedness.) Of the left-handed men, 46% (12/26) were first born, 15% (4/26) were second born, and 38% (10/26) were later born. Of the right-handed men, 23% (21/90) were first born, 37% (33/90) were second born, and 40% (36/90) were later born. Significantly more of the left-handed men were first born and significantly more of the right-handed than left-handed men were second born (p=.01)" (London WP, Kibbee P, Holt L (1985) Handedness and alcoholism. J Nerv Ment Dis 173(9):570-571)

"The other finding in the Smart sample concerned children of 21 mothers who had their first-born child at 39 years or older; 9 (43%) of the children were non-right-handed. In the NCDS survey there were no significant effects for maternal or paternal age (McMannus, 1981)." (Annett, Marian (1985) Left, Right, Hand and Brain: The Right Shift Theory London: Lawrence Erlbaum pp. 75)

"As early as 1966, Valerie Grant, a psychiatrist at the University of Auckland in New Zealand, noticed an apparent tendency for women who subsequently gave birth to boys to be more emotionally independent and dominating than those who gave birth to girls. She tested the personalities of eighty-five women inthe first trimester of pergnancy using a standard test designed to distinguish "dominant" from "subordinate" personalities---whatever that may mean. Those who later gave birth to daughters averaged 1.35 on the dominance scale (from 0 to 6). Those who later gave birth to sons averaged 2.26, a highly significant difference." (Ridley 1993: 120, The Red Queen)

"There are many well-established natural factors that bias the sex ratio of human offspring, proving that it is at least possible. The most famous is the returning-soldier effect. During and immediately after major wars, more sons are born than usual in the belligerent countries as if to replace the men that died. (This would make little sense; the men born after wars will mate with their contemporaries, not with those widowed by the war.) Older fathers are more likely to have girls, but older mothers are more likely to have boys. Women with infectious hepatitis or schizophrenia have slightly more daughters than sons. So do women who smoke or drink. So did women who gave birth after the thick London smog of 1952. So do the wives of test pilots, abalone divers, clergyman, and anethetists. In parts of Australia that depend on rainfall for drinking water, there is a clear drop in the proportion of sons born 320 days after a heavy storm fills the dams and churns up the mud. Women with multiple sclerosis have more sons, as do women who consume small amounts of arsenic. Finding the logic in this plethora of statistics is beyond most scientists at this stage. William James of the Medical Research Council in London has for some years been elaborating a hypothesis that hormones can influence the relative success of X and Y sperm. There is a good deal of circumstantial evidence that high levels of the hormone gonadotrophin in the mother can increase the proportion of daughters and that testosterone in the father can increase the proportion of sons. Indeed, Valerie Grant's theory suggests a hormonal explanation for the returning-soldier effect: that during wars women adopt more dominant roles, which affects their hormone levels and their tendency to have sons. Hormones and social status are closely related in many species; and so, as we have seen, are social status and sex ratio of offspring. How hormones work, nobody knows, but it is possible that they change the consistency of the mucus in the cervix or even that they alter the acidity of the vagina. Putting baking soda in the vagina of a rabbit was proved to affect the sex ratio of its babies as early as 1932." (Ridley 1993: 122-3, The Red Queen)

"Stater (1962) found that mothers of homosexual sons were significantly older than a general population sample at the time of the son's birth."(Evans, R. (1972) Physical and biochemical characteristics of homosexual men. Journal of Consulting and Clinical Psychology 39: pp. 142) [higher T]

"Associations between birth order and lateral preferences of hand, eye and foot were examined in a sample of 6436 black seven year old boys and girls whose mothers participated in the Collaborative Perinatal Project (CPP) in Philadelphia. Overall, most of the subjects (87%) showed right hand preference, and the majority of subjects showed right eye (55%) and foot (63%) preferences. Analysis of cross preferences indicated some tendency for a consistent right side orientation. However, patterns of lateral preferences were similar for both boys and girls across seven birth order groups." The data were interpreted as showing that birth order and lateral preferences are not interrelated. (Nachshon, I. & Denno, D. (1986) Birth order and lateral preferences. Cortex 22 (4): 577)

"The handedness of 1,186 children about to enter kindergarten was tested. The sample represented approximately 98 percent of all children of this age in a school system during 8 years. Handedness was examined in relation to birth order, maternal age at birth, and sex, for 1,097 subjects (92.5%), and in relation to season of birth for the total sample. The finding that there were significantly more nonright-handed boys for birth orders one and four-or-later, than for two and three, provides support for Bakan (1971). There was a nonsignificant increase in nonright-handedness for boys born to the youngest (less than 20) and oldest (less than 30) mothers. A significant seasonal effect for the birth of nonright-handed boys was observed. For each of the fall and winter months (September - February) the proportion of nonright-handed male births was higher than that for any of the spring and summer months. For girls, no significant effects on handedness were observed, for birth order, maternal age, or season of birth." (Badian, N.A. (1983) Birth order, maternal age, season of birth, and handedness. Cortex 19 (4): 462)

"Several neurological and immune phenomena associated with cerebral laterality also show an atypical season of birth pattern. Alcoholism is also associated with cerebral laterality. In this pilot study (n = 292), 66% of right-handed alcoholic men were born during the summer and fall (expected 52%, p less than 0.001). This finding suggests that at high latitude more right-handed men would become alcoholic because seasonal effects usually intensify with increasing latitude. In addition, in our sample of alcoholic men, left-handedness was associated with having an alcoholic father or with being first-born. Together, these findings suggest that the prevalence of alcoholism should increase with increasing latitude, and that the frequency in alcoholic men of being left-handed, first-born or having an alcoholic father should decrease with increasing latitude. The available literature tends to substantiate these correlations, but more systematic studies of season of birth and correlations with latitude in alcoholism are required." (London, W.P. (1987) Alcoholism: theoretical consideration of season of birth and geographic latitude. Alcohol 4 (2): 127)

"Stater (1962) found that mothers of homosexual sons were significantly older than a general population sample at the time of the son's birth." (Evans, R. (1972) Physical and biochemical characteristics of homosexual men. Journal of Consulting and Clinical Psychology 39: pp. 142) [higher T]

"Handedness and birth order: birth order 1 and 4+ 64 left, 396 right; birth order 2-3 34 left, 341 right. X2 = 4.69, df = 1, P = 0.05" (Bakan, P. (1977) Left handedness and birth order revisted. Neuropsychologia 15 (6): 838)