Effect of Birth Order on the Differential Parental Treatment of Children

This study investigated the effect of birth order on the differential parental treatment of children. Respondents of the study include 122 adolescents (33 males and 89 females) from the Klang Valley, Malaysia aged 13-17years (M=16years, SD = 1.05). The Sibling Inventory of Differential Experience (SIDE) was used to measure differential parental treatment. Findings of the study revealed significant differential parental control between first and last born children. Future studies may examine the number of siblings in a family as a factor in differential parental treatment.


Rational for the Study
Psychologists have often wondered how a sociable humorist and a solitary, thoughtful intellectual can be so dissimilar and yet share the same genetic factor.The secret some scholars argue lies within the context of birth order.Birth order indicates the position of a child in a family relative to their siblings.In the contention of Sulloway (1996), last born children are often rebels whose views center on changing the world, while first born children simply stick to the "status quo".In consonance with the above, MacDonald (1971) argued that last born children were likely to have external-locus of control, meaning they believe that external forces control their behaviour, while first born children he argued have internal-locus of control, which implies they believe that they themselves, and not the external ecosystem, control their behaviour.
Although physical trait may bear some resemblance among siblings due to genetic similarity, however personality trait and the developmental pace of siblings vary due to the non-shared environmental factor in the family (Daniels & Plomin, 1985).In view of the above, a considerable number of researchers have reported differences in parental treatment based on birth order between first born and later born children (Daniels, Dunn, Furstenberg, & Plomin, 1985).The importance of birth order in personality development was first proposed by Alfred Adler (1956).The scholar contended that first born children differ from last born children.Adler's theory was later supported by Sulloway's (1996).In the contention of both scholars, parents normally treat their children differently based on their birth order.Although, individual differences such as birth order, gender, and temperament may cause differential parental treatment, parents adjust to their children according to their needs and signals (Kothari, 2011).
The ordinal position of children reinforces, and fosters some of the behavioral differences among siblings (Nyman 1995).It is generally believed for example, that firstborns tend to be more intellectually oriented than their younger siblings, are more conscientious in their work habits and studies and attain higher levels of professional status in life (Herrera, Zajonc, Wieczorkowska, & Cichomski 2003).Essentially, dominance hierarchies are based on age in most families.Firstborns can easily intimidate their younger brothers and sisters both physically and verbally and as a result usually exert dominance over them.Several aspects of personality and behavior, expressed within the family, reflect these differences in dominance (Howe & Recchia, 2006;Nash, 2009).In line with the above, research has suggested that the birth order of children influences the treatment they receive from their parents, with the youngest child being favoured by parents (Rohde et al., 2003).
Nevertheless as compared with later born children, first born, are usually expected to be adult models and to conform to adults' expectations and pressure (Baskett, 1985).Hence, parents have more expectations towards the first born as compared to their last born.Therefore, first born children may feel controlled by parents.Parental control weakens from first born to last born, while the last born continues to enjoy some advantage.Parents tend to discipline first born children more than other siblings in the family in most societies.In this regard, the theory of differential discipline contend that last born children face more lenient disciplinary environment as compared to first born children (Hotz & Pantano, 2010).
Studies have also found mothers more interactive and responsive towards their first born child as compared to the last born (Collins, 2006), this could be because new parents may be overly anxious about the first child and as the second child arrives, attention is divided among the siblings.This is supported by parental investment theory (Trivers, 1972) and modern dilution theory (Harkonen, 2012).Modern dilution theory argues that when parents are faced with the task of raising children born at different times, they usually decrease the resources and inputs attainable for other offspring still under parental care (Behrman & Taubman, 1986).In contrast, Hertwig, Davis and Sulloway (2002) contended that parents try to split their resources equally among all their children.
The notion of egalitarian treatment has remained a challenged and inconclusive phenomenon particularly whether parents treat the younger or older children differently.Again siblings' perception of unequal treatment may be the consequence of their understanding of the phenomenon (Hertwig et al., 2002).In view of the above relations, the current research by focusing on parents treatment towards their children, aims to discover Malaysian parenting style based on birth order.

Procedure
This is a cross sectional study, with 122 students recruited randomly from high schools.The initial instrument administered by the researcher was 137; of this number 15 were rendered void.The inclusion criteria suggest that adolescents must either be first born or last born in the family and their parents must still be married.To participate in the study, students were urged to provide their consent.Permission for the study was granted through the respondent's parents and the principals of participating schools.

Measures
Sibling Inventory of Differential Experience (SIDE; Daniels & Plomin, 1985) was used to measure non shared family environmental influences by asking children to compare their environment to that of their siblings.The current version of SIDE was designed for adolescents in junior and senior high school (i.e. 12 to 18 years).The 9-item scale was rated on a five point Likert scale based on two dimensions of affection and control toward the first versus the last born child (1 = much more toward my sibling to 5 = much more toward me).The five items which measures parental affection consisted of parental pride, interest, favoritism, enjoyment and sensitivity whereas another four item measuring parental control consists of parental strictness, punishment, blame, and discipline.
The reliabilities for younger siblings perceiving differential parental treatment from their parents were α = .74and .64 as for older siblings α = .71and .64.The internal consistency recorded a cronbach alpha coefficient of α = .79and .84 for control and affection among children (Kowal, Krull, & Kramer, 2006).The total score ranged from 1 to 5. Higher scores indicated higher affection or control from either parent, while lower scores indicated otherwise.Mid score however, indicated that siblings were treated equally.Students and parent were also given demographic forms to fill, these included details such as their age, gender and so on.

Discussion
The study examined the differences in parental differential treatment (PDT) between first born and last born children.Results demonstrated no significant difference in parental affection and maternal scores between first and last born.However, there was a significant difference [t (120) = 3.03, p < .01] between first and last born in differential paternal control scores.The results of the study further found no significant difference between first and last born children in differential parental treatment scores with parents' being more affectionate towards the last born and controlling for the first born.Although the study did not find any significant difference between first and last born scores in parental treatment, the finding illustrated how parents offer and give their best to their last born as they need more help than the rest.The finding of the present study is consistent with previous studies (Hotz & Pantano, 2010;Poonam & Punia, 2012;Rohde et al., 2003).The finding is also in consonance with the Jenkins, Rasbash, and O'Connor's (2003) study that discovered no association between differential parenting and birth order.
There was a significant difference in paternal control between first and last born children.It is appear that the feeling of being controlled by father is higher among firstborns.One reason could be that fathers may have the responsibility and authority to make decisions which coincide with the developmental level of the child (Poonam & Punia, 2012).Existing evidence revealed that paternal behaviour plays a crucial role in the development of first born children which could be the reason behind paternal control towards first born.Fathers have a higher expectation of their first born child because they are expected to model paternal behaviour in their interaction with their siblings (Baskett, 1984).It seems that the firstborn children frequently play the role of parent surrogate to their younger siblings.
In Asian culture, paternal control is associated with warmth and affection whereas maternal control is associated with aggression or hostility (Kim, 2008).Given the role of fathers in Asian cultures as decision makers, leaders and the firm parent (Kim & Choi, 1994), paternal control becomes necessary.Besides that, fathers more than mothers perceive their expression of behavioural control as appropriate for adolescents (Kim, 2008) and encourage the development of self-control in the child.On the other hand, studies have also found first born children more attuned to differences in parenting and treatment compared to later born children (Crouter, Head, McHale, & Jenkins-Tucker, 2004;Shebloski, Conger, & Widaman, 2005).However, such speculations need to be further explored by future studies by examining the cultural background of participants as a factor that influences differential parental treatment.
As the of published papers, the current study is not without limitation.Most participants recruited were females; this may have affected the results of the study, given that a past study also found girls particularly vulnerable to adverse treatments such as behavioural control and discipline from fathers (Shanahan, McHale, Crouter, & Osgood, 2008).Earlier studies also proposed that females are more controlled and supervised compared to boys (Begue & Roche, 2005).One of the strengths of this study was that adolescents view on differential parental treatment was taken into account since many previous studies only emphasized differential maternal treatment (McGuire, Dunn, & Plomin, 1995;McHale & Pawletko, 1992).
It is suggested that future studies may also take into account the gender of siblings as an influential factor in differential parental treatment, which the earlier study by Poonam and Punia (2012), discovered differential parental treatment as distinct in opposite sibling sex dyads as compared to similar sex sibling dyad.In addition, family size and marital satisfaction are also important variable that may affect the differential positivity portrayed by parents (Jenkins, Rasbash, & O'Connor, 2003).Although previous studies have demonstrated that parents with more children were less positive towards their children (Kidwell, 1981), however, the relationship between family size and differential positivity between parents have not really been investigated (Jenkins et al., 2003).
In conclusion, this study found that the birth order of children made a difference in paternal control, with fathers more controlling towards their first born more than their last born.Findings of this study could be used by school counselors, parents, psychologist, and teachers in understanding the factors responsible for differential parental treatment and the steps to educate parents about the impact of their parenting behaviour in the development of their children.

Table 2 .
Comparison of parental differential treatment scores between first born and last born