Relationship between IQ and Birth Order - Research Paper Example

? The causes of birth order and family size on IQ and personality of the of the December 23, The causes of birth order and family size on IQ and personality Introduction The relationships among birth order, family size, Intelligence Quotient and personality have attracted the attention of researchers, scholars and psychologists for decades. Questions such as whether one’s birth order and family size have any significant influences on one’s IQ or personality have been subjected to number of debates and studies. Among these the relationship between IQ and birth order assumes greater significance as various theories such as resource dilution model, the Confluence Model, and the theory of standard diminishing utility have offered their own interpretation regarding the relationship between the two. Similarly, the relationship between personality and birth order has assumed new dimensions with Alfred Adler’s postulation that each birth position has its own personality traits. In the same way, previous literature has clearly shown the potential power of family size to influence the personality as well as the IQ of children. This paper seeks to unearth the relationship between birth order and IQ, birth order and personality, family size and IQ, and family size and personality; in doing so the paper also deals with the major counter arguments for each of these relationships. Relationship between IQ and birth order Black, Devereux and Salvanes (2011) conducted some remarkable studies on the effects of birth order on IQ; they identified a strong and significant effect of birth order on IQ as earlier born children develop more of IQs than the younger ones. However, the authors identified that no genetic component could be associated with birth order. The quality of pre-natal care and the behavioral pattern of the mothers can considerably get changed with the passage of time. There are a number of theories and models that support the relationship between IQ and birth order. For instance, the resource dilution model holds that the later born children may lack those parental resources offered to the firstborns. It has been pointed out that “firstborns may benefit from having the exclusive attention of their parents, while later borns have to share time with their earlier-born siblings” (Black, Devereux and Salvanes, 2011, p. 114). The Resource Dilution Model proposed by Blake postulates that parental resources are quite finite and parents with more than one child have to divide these resources among their children (Esping, 2003). On the other hand, the first born unlike the late born receives the complete attention of the mother which has a positive impact on the cognitive development of children. The resource dilution model best explains why firstborns form a large majority of the college population of the nation. In the same way, the Confluence Model proposed by R.B. Zajonc & Markus also highlights the firstborn IQ advantage as they receive the maximum share of parental attention and experience better intellectual environment at home (Esping, 2003). The model also holds that firstborns from smaller families are better equipped than those from larger families to develop higher IQ scores. In the same way, the theory of standard diminishing utility also echoes the diminishing resources and care shown by mothers towards younger childen. For Kristensen and Bjerkedal (2007, p. 1717), prenatal or gestational factors have the potential to affect the fetal brain. This has also been pointed out by Spiker et al (2001, p. 456) that “maternal antibodies are sensitized to fetal brain tissue and affect the neuronal substrate of cognitive abilities in the secondborn or laterborn sibs” (Spiker et al., 2001, p. 456). Similarly, a study on nonverbal IQ scores conducted by Spiker et al. (2001, p. 449) among a sample of 144 autism multiplex families clearly demonstrated that “nonverbal IQ scores were significantly lower in secondborn compared with firstborn siblings with autism.” The study thus confirmed the correlation between birth order and nonverbal IQ scores among autism multiplex families. These birth order effects on non-verbal IQ are “produced by interactions between autism susceptibility genes and postnatal environmental factors” (Spiker et al., 2001, p. 456). The decreased parental attention towards younger children is instrumental for this negative non-verbal IQ. The tutoring role played by the firstborns also offer them superior IQ than their younger siblings as this helps them to improve their verbal abilities as well as cognitive information processing. Personality and birth order The relationship between birth order and one’s personality traits has attracted the attention of many researchers ever since Alfred Adler postulated that each birth position has its own personality traits. Adler’s theories depicted the firstborns “as leaders, high-achievers, ambitious, and conforming” who “attempt to please their parents via traditional ways, which are through academic performance and responsible behaviors” (Sun Ha & Tam, 2011, p. 28). On the other hand, the middle and last born children fail to ‘monopolize parents’ attention’ and being aware of the higher status of the firstborn, they seek “alternative strategies to stand out from their siblings” (Sun Ha & Tam, 2011, p. 28). Thus, Adler strongly believed that birth order has a significant role in shaping one’s personality. Lauren (2012), commenting on the personality traits by birth order, purports that the eldest child is self-confident, “authoritative, strict, direct, and confrontational” whereas the younger ones are more agreeable, resistant, irresponsible and freedom loving (Lauren, 2012, para 2). In the same way Sulloway held that birth order position has a pivotal effect on personality development. For him, each child competes to earn parental investment and very often the firstborns dominate the younger siblings to receive a major share of the parental investment. According to Sulloway, firstborns receive greater investments from their parents and as a result they “tend to be more amenable to their parents’ wishes, values, and standards than their laterborn siblings, as well as more conscientious, responsible, ambitious, organized, and academically successful, more traditional and conservative, and more likely to endorse conventional morality” (Healey and Ellis, 2007, p. 55). On the other hand, the late borns need to undergo dominion and bullying from their older siblings and these will make them more empathetic and egalitarian towards the suffering humanity while being resistant and at times rebellious to authorities. They are also likely to be agents of social change in the society. In the same way, the first borns usually possess “higher levels of leadership and competitiveness, whereas later borns and females exhibit more cooperation and flexibility” (Healey and Ellis, 2007, p. 56). Thus, in Sulloway’s opinion, birth order results in differences within families and each of the siblings resorts to various strategies to maximize their parental share. However, one should bear in mind that Sulloway’s theories cannot be applied to the case of siblings with wide birth intervals. The comparison is made between those siblings who are born and raised together without any wide birth intervals. In the same way, the first born children get better opportunities to develop their personality and to serve as intellectual resources in comparison to later born children. Similarly, the resource dilution hypothesis also holds that it is the first born who receives undivided parental resources whereas the younger ones receive only a share of parental attention and care. All these reflect in the personality traits of children as well. In this respect, Dixon, Reyes, Leppert & Pappas (2008) undertook a remarkable study among 361 siblings belonging to 42 large families to identify the relationship between birth order and personality traits. The participants were assessed based on the personality traits of Psychoticism, Extraversion and Neuroticism. The results of the study revealed that birth order plays a significant role in molding one’s personal traits. The authors identified that each child plays a unique sibling niche role; for instance, the younger ones turn out to be more of extraverts in their efforts to gain recognition and attention. In comparison to the older ones they possess greater sense of sociability and they also exhibit behaviors associated with psychoticism. Healey and Ellis (2007, p. 58) adopted a within-family research design to test Sulloway’s model which ensured that all the participant sibling pairs were born and brought up in the same household. The results of the study highlighted Sulloway’s family-niche model of personality development as these offered testimony for Sulloway’s theoretical formulations. IQ and family size Having dealt with the relationship between birth order and IQ, it is essential to know how family size and IQ are related. For this, one needs to go through the theories of Zajonc and Blake on family size and IQ, and compare them with Rodgers’ postulation that neither family size nor birth-order has any significant effects on IQ. It has been argued that children in small families have higher IQs than those in large families with large number of siblings (Abdel-Khalek & Lynn, 2008, p. 1033). It was Lynn (1959) who first postulated that children in small families receive greater attention from parents than those in larger families. The studies based on this assumption prompted Zajonc formulated the confluence theory while Blake and Downey sought to explain the relationship between family size and IQ using the resource dilution theory. While Zajonc’s confluence theory holds that “the child’s IQ is partly determined by the attention that parents and siblings give to it” Blake and Downey argue that ‘‘parental resources are finite and that as the number of children in the family increases, the resources accrued by any one child necessarily decline’’ (Abdel-Khalek & Lynn, 2008, p. 1033). Thus, both the theories favor small families for increased levels of IQ for the children. While both the theories stress that the first born child always gets more attention from the parents they also mean that in larger families the IQ levels of children tend to diminish as parental attention given to the child decreases by birth order. This has also been pointed out by Esping (2003) when the author observes that in larger families “the general intellectual environment becomes less mature” and as a result “firstborns and older children from large families have lower IQs than firstborns and older children from smaller families.” Similarly a study conducted by Lillian Belmont and Francis Marolla in 1973 on nearly the entire population of 19 year-old Dutch men showed that children from larger families get poorer intelligent test scores and they also found that the first borns had a comparatively better IQ score than the younger ones (Esping, 2003, para 4-5). However, Rodgers and his colleagues purported that neither family size nor birth-order is related to one’s IQ. They argued that the so called relationship between family size and IQ envisioned by Zajonc, Blake and Downey is present only in the between-family data used by them whereas that within-family data do not show such relationships (Abdel-Khalek & Lynn, 2008, p. 1034). The findings of Rogers and his colleagues will be discussed while dealing with the counter arguments. Personality and family size Family size is a significant factor in molding the personality of children as children learn a number of values, skills and social behavior from their family members. However, with regard to personality how children are raised assumes more importance than how and where they were born. The theories on birth order and personality are equally applicable to the issue of personality and family size. Parental attention, investment and care are necessary prerequisites for the personality development of any children. These are best possible in small families where the parents can spent their maximum investment for the children. However, it is a fact that children in larger families tend to acquire a number of social and interpersonal skills. However, larger families tend to assist the older siblings whereas the younger ones fail to receive ample attention. According to Zajonc’s model the older siblings in larger families can develop their own personalities through tutoring the younger ones. This also promotes their intellectual growth. On the other hand, the lastborns are negated of such opportunities. This has been pointed out by Sulloway (2007, p. 1712) when the author observes: “…teaching younger sibling is posited to benefit the tutor more than the learner, especially since lastborns have no one to tutor.” Familial intellectual environment, values and social behavior patterns also influence the personality of children whether they live in small or larger families. The amount of attention children receives from parents and older siblings have a positive impact on the personality development of the child. Counter argument: Relationship between IQ and birth order There are many who regard the relationship between IQ and birth order as false. Even though the hypothesis stresses that the firstborns tend to have greater IQ than their younger siblings no authentic studies have been able to come up with a considerable difference of IQ scores between the two sects. In 1973 researches carried out by Belmont and Marolla showed that the relation of IQ and birth order is quite negative. Later, Kristensen and Bjerkedal tested the relation between IQ and birth order among a large Norwegian sample and the results of the study clearly pinpointed that “the relation between birth order and IQ score is dependent on the social rank in the family and not birth order as such” (Kristensen and Bjerkedal, 2007, p. 1717). The authors also rejected the notion of increased maternal antibody attack on the fetal brain with higher birth orders. The child’s role within the family, his social exposure, and environmental factors were more significant predictors of one’s IQ or intelligence rather than one’s birth order. Boomsma et al. (2008, p. 633) also replicate that the association between IQ and birth order is negative and the authors show how “the effect of birth order on IQ is reversed in some studies” where second-borns or third borns score higher on IQ than the first-borns. Similarly, it can also be seen that twins who have the same birth order and who live in the same environment do not possess the same IQ scores. One can thus infer that genetic factors and environment exert great influence on one’s than his/her birth order. Counter argument: Personality and birth order It is also worthwhile to analyze the arguments repudiating the relationship between birth order and personality. It was Ernst and Angst (1983) who first came to the conclusion that “most birth-order effects on personality were methodological artifacts that disappeared when confounds such as socioeconomic status and family size were taken into account” (Healey and Ellis, 2007, p. 55). While birth order contributes to the personality of children one can never undermine such contributing factors as the size of the family, the socio-economic milieu and the family environment. Similarly, only very few studies resorted to within-family design where the participant sibling pairs were born and raised in the same family environment. Also, environmental factors exert great influence on one’s personality similar to that of genetic factors. As rightly pointed out by Lauren, “the correlations of personality in and out of the home are due to the genetic factor, while the differences are due to the environmental factor” (Lauren, 2012, para 8). Thus, a true understanding of the actual nature and depth of the relationship between birth order and personality necessitates more comprehensive researches in this regard. It is therefore imperative that further in-depth studies are undertaken to see the extent to which birth order influence the personality of children. Counter argument: IQ and family size It was Rogers and his colleagues who opposed the so called relationship between family size and IQ envisioned by Zajonc, Blake and Downey and they argued that the findings made by these researchers are applicable only in the case of between-family data whereas within-family data do not support their observations. Abdel-Khalek and Lynn (2008) undertook a remarkable study to examine the relation between intelligence, birth order and family size. The participants of the study was comprised of 4643, 8–15 years old in Kuwait. The results of the study do not support the theories of Zajonc or Blake whereas they went in tune with the conclusions made by Rodgers and his colleagues that “family size and birth-order have no causal effects on intelligence” (Abdel-Khalek & Lynn, 2008, p. 1038). The study identified that there is only a negligible family size effect- a slight tendency for the first born children to have higher IQs than the younger ones. However, the authors point out that “later born children tend to have older parents and that older mothers tend to have a higher incidence of conditions that adversely affect the intelligence of their children” which has nothing to do with the family size (Abdel-Khalek & Lynn, 2008, p. 1037). Thus, it can be seen that family size is not a significant predictor of the IQ level of children. Counter argument: Personality and family size There is no doubt that family size affects the personality of children either positively or negatively. However, even though children, especially firstborns in small families, tend to display more of IQ levels the same cannot be said of personality development. As pointed out by Abdel-Khalek & Lynn (2008, p. 1033), in larger family sizes, each child should receive progressively less attention from the parents, and IQs should decline steadily with birth order.” Similarly, it has also been observed that familial intellectual environment diminishes with increased family size and as a result the first borns benefit most from higher intellectual environments (Sun Ha & Tam, 2011, p. 29). However, whether children live in small or large families their personality is shaped by their experiences, environment and the way they are being treated by the family members. In larger families the younger ones can benefit from the experiences, care and affection of many older ones and this could be an added advantage to them. However, one can never say that only by living in a small or large size family one’s personality will better be formed. Conclusions To conclude, it can be stated that there exists a sound relationship between birth order and IQ just as birth order is also associated with one’s personality. On the other hand, one can find a positive relationship between family size and IQ whereas the relationship between family size and personality needs further researches. The study has made it clear that firstborns are more likely to have higher IQs compared to younger ones. Both the resource dilution model and the Confluence Model emphasize the firstborn IQ advantage as they receive the maximum share of parental attention and parental resources. However, one needs to take into account the social rank of the child in the family as well. The relationship between personality and birth order is also evident in the literature. While Adler’s theories depict the firstborns “as leaders, high-achievers, ambitious, and conforming” it is a fact that the younger siblings are subjected to live in the firstborns’ shadow (Sun Ha & Tam, 2011, p. 28). In the same way, Sulloway’s studies also show that firstborns always dominate the younger siblings to receive a major share of the parental investment (Healey and Ellis, 2007). However, one should also take into account such contributing factors as the size of the family, the socio-economic milieu and the family environment. Regarding IQ and family size, children in small families are likely to have higher IQs than those in large families with large number of siblings (Abdel-Khalek & Lynn, 2008). While Zajonc, Blake and Downey favor small families for increased levels of IQ for the children, Rodgers and his colleagues caution that these findings cannot be applied to within-family data. Similarly, Family size is a significant factor in molding the personality of children. However, with regard to personality how children are brought up is more significant than how and where they are born. Therefore, one cannot state that either small families or large families are better suited for one’s personality development. References Abdel-Khalek, A.M & Lynn, R. (2008). Intelligence, family size and birth order: Some data from Kuwait. Personality and Individual Differences, 44, 1032–1038. Black, S.E., Devereux, P.J & Salvanes, K.G. (2011). Older and wiser? Birth order and IQ of young men. CESifo Economic Studies, 57(1), 103-120. Boomsma et al. (2008). Intelligence and birth order in boys and girls. Intelligence, 36, 630–634. Dixon, M.M., Reyes, C.J, Leppert, M.F & Pappas, L.M. (2008). Personality and birth order in large families. Personality and Individual Differences, 44, 119–128. Esping, A. (2003). Does Birth Order Affect Intelligence? Retrieved December 19, 2012 from http://www.indiana.edu/~intell/birthOrder.shtml Healey, M.D & Ellis, B.J. (2007). Birth order, conscientiousness, and openness to experience Tests of the family-niche model of personality using a within-family methodology. Evolution and Human Behavior, 28, 55– 59. Kristensen, P & Bjerkedal, T. (2007). Explaining the Relation Between Birth Order and Intelligence. SCIENCE, 316, 1717. Lauren. (2012). Birth Order's Effect on Personality. Retrieved December 19, 2012 from Serendip website: http://serendip.brynmawr.edu/exchange/node/7444 Spiker et al. (2001). Birth Order Effects on Nonverbal IQ Scores in Autism Multiplex Families. Journal of Autism and Developmental Disorders, 31(5), 449-460. Sulloway, F.J. (2007). Birth Order and Intelligence. SCIENCE, 317, 1711-1712. Sun Ha, T & Tam, C.L. (2011). A Study of Birth Order, Academic Performance, and Personality. International Conference on Social Science and Humanity IPEDR, 5, 28-32. Read More