生物谷報道：對挪威青少年進行的一項最新研究顯示,，兄弟姐妹之中老大的智商最高,，他們的IQ測試得分往往比弟弟妹妹們高出2.3分?？茖W家認為,，這一現(xiàn)象并非源于生理因素，而是所謂的“家庭動力學”的結(jié)果,。相關(guān)論文發(fā)表在6月22日的《科學》雜志上,。
長期以來人們就認為如果從足夠大的人口樣本取樣,，長子或長女比弟弟妹妹們更聰明。在現(xiàn)實生活中,，很多“老大”在社會上地位顯赫,。一些研究甚至表明，出生次序與智商之間存在著某種關(guān)系：越晚出生,，智商越低,。
不過，許多人對這一關(guān)系的可信度表示懷疑,，至于其背后的深層原因更是眾說紛紜。有些批評家認為,，智商相對較低的家庭往往比較龐大,，兄弟姊妹眾多使得每個人獲得功課輔導的時間較少，因此,，越晚出生的孩子往往越不聰明,。
在最新的研究中，挪威奧斯陸大學（University of Oslo）的Petter Kristensen和挪威武裝軍隊醫(yī)學服務(wù)機構(gòu)（Norwegian Armed Forces Medical Services）的Tor Bjerkedal對241310名挪威青少年進行了研究,，他們的年齡都是18或19歲,，很適合進行智商檢測。
研究人員發(fā)現(xiàn),，頭胎孩子的平均IQ得分超過了103,，而第二胎孩子僅超過100，第三胎約為99,。然而,，由于老大夭折而“晉升”成為老大的孩子，他們的平均IQ得分也能達到103,。
研究人員在另一項單獨分析研究中發(fā)現(xiàn),，這一總體趨勢也適用于單個家庭，也就是說先出生的孩子智商更高,。這項單獨研究將發(fā)表在近期的《智力》（Intelligence）雜志上,。
究竟是什么造成了同胞間的智商差異呢？Kristensen認為,，這是家庭和社會因素造成的,，比如父母對長子長女的關(guān)注較多，而且年長的孩子會花時間教育幫助弟弟妹妹等等,。
Kristensen自身是第二個出生的孩子,，他表示，一開始自己憑直覺的判斷,，不相信越早出生的孩子越聰明,，尤其是還有研究表明,，第二胎和第三胎孩子的健康狀況往往比老大更好。
美國加州大學伯克利分校的Frank Sulloway表示,，該研究結(jié)果并不能說明家庭中較小的孩子一定會受到智力較低的不良影響。他說,，“許多證據(jù)已經(jīng)表明,，第一個出生和后來出生的孩子所擅長的是不同的事情。”比如達爾文,，雖然他是六個孩子中第五個出生的,，一些功課也不是很好，但他是一個有巨大好奇心的人,。Sulloway說,，“如果讓我在IQ上多2.3分和擁有達爾文的巨大好奇心之間做出選擇，我會毫不猶豫地選擇后者,。”（引自科學網(wǎng) 任霄鵬/編譯）
原始出處：
Science,， 22 June 2007:
Vol. 316. no. 5832, p. 1717
DOI: 10.1126/science.1141493
Explaining the Relation Between Birth Order and Intelligence
Petter Kristensen1,2* and Tor Bjerkedal3
Negative associations between birth order and intelligence level have been found in numerous studies. The explanation for this relation is not clear, and several hypotheses have been suggested. One family of hypotheses suggests that the relation is due to more-favorable family interaction and stimulation of low-birth-order children, whereas others claim that the effect is caused by prenatal gestational factors. We show that intelligence quotient (IQ) score levels among nearly 250,000 military conscripts were dependent on social rank in the family and not on birth order as such, providing support for a family interaction explanation.
1 National Institute of Occupational Health, N-0033 Oslo, Norway.
2 Section for Preventive Medicine and Epidemiology, University of Oslo, N-0318 Oslo, Norway.
3 Institute of Epidemiology, Norwegian Armed Forces Medical Services, N-0015 Oslo, Norway.
* To whom correspondence should be addressed. E-mail: [email protected]
The interest in the relation between birth order and intelligence dates back to Sir Francis Galton's English Men of Science (1). Galton found more firstborn sons in prominent positions than what he attributed to chance. This was the start of numerous studies; one of the most influential was a Science publication in 1973 showing a negative association between birth order and intelligence in young Dutch men (2). Since then, sociologists, psychologists, and demographers have proposed several explanatory models (3). The most influential models have emphasized explanations relating to interactions within the family and favorable conditions for intellectual stimulation for low-birth-order children.
Several researchers have claimed that the relation between birth order and intelligence is false, confounded by factors relating to family size: Families with low-intelligence children tend to be large, and the relation with birth order is an artifact when comparisons between families are made (3). This explanation would not produce birth order effects between siblings. Thus, the demonstration of small but notable birth order effects on intelligence quotient (IQ) in large studies examining relations within families (4, 5) contradicts the idea that artifact is the full explanation.
A third model claims that the relation is explained by prenatal or gestational factors. One hypothesis suggests an effect of maternal antibody attack on the fetal brain: Maternal antibody levels tend to increase by higher birth orders in a suggested mechanism parallel to rhesus incompatibility and erythroblastosis (6). It has been shown that children of mothers with autoimmune disease have an increased risk of learning disabilities [for example, (7)], but there are no empirical data to support immunoreactivity in explaining the birth order effect.
