Sibling relationship has a longer duration than most of the other relationships, starting from the birth of the youngest sibling relation phase and continuing until the end of life span (Cicirelli, 1991). Siblings have a common history, including many shared experiences in addition to having a large proportion of shared genetic variance (Cicirelli, 1995). Throughout the life, intimacy and closeness of sibling contact waxes and wanes; however, sibling relationship strongly affects well-being and psychosocial functioning (Noller, 2005; Sherman, 2006). Today, about ninety percent of individuals have a sibling and many researchers emphasize the importance of sibling relationships through childhood and adulthood (Milevsky, 2011).  Siblings have the privilege of teaching one another and they can provide modeling and reinforcement for one another. Research has also shown that the quality of sibling relationships influences child’s adjustment, particularly in the period of adolescence, in which identity and autonomy development are of key importance (Dunn et al., 1994).

Siblings’ positive and negative behaviors and feelings about each other during childhood are significantly correlated with the quality of sibling relationships later in early adolescence. Thus, the nature of the sibling relationship in the childhood period could extend into the adolescence period. However, a good sibling relationship in childhood does not guarantee the same good sibling relationship later in adolescence. The nature of sibling relationships may change during adolescence, associated with the biological, cognitive and social changes that take place during adolescence (Buhrmester, 1992; Dunn, 1992; Dunn et al.., 1994; Steinberg and Morris, 2001). Sibling relationships are transformed during adolescence to reflect less companionship, less intimacy, less affection and more equality because siblings become more similar in competence and developmental status as they grow up (Updegraff et al., 2002; Buhrmester, 1992; Buhrmester and Furman, 1990). On the other hand, these decreases should not be interpreted as meaning that sibling relationships in adolescence become less important. Sibling relationships in adolescence can still be characterized by closeness. Adolescents’ relations with their siblings are closer than those with their parents (Lempers and Clark-Lempers, 1992). In general adolescents have a tendency to escape from the influence of their parents, but siblings still provide advice about life plans and personal problems during this period (Tucker et al., 1997).

Sibling relationship quality during adolescence has an influence on developmental outcomes. Positive sibling relationships are associated with numerous benefits related to social, emotional and healthwise development throughout adolescence. These benefits include, yet not limited to, higher peer competence (Kim et al., 2007), prosocial behavior (Brody et al., 2003; Whiteman et al., 2007), academic engagement (Bouchey et al., 2010), personal achievement (Wheeler, 2012), healthy emotion regulation (Kennedy and Kramer, 2008), high level of self-regulation (Walker et al., 2010) and better adjustment (Noller, 2005; Pike, Coldwell and Dunn, 2005). On the other hand negative sibling relationships are associated with adolescents’ risky behaviors, adjustment problems, school problems, bullying (Bank et al., 2004; Stocker et al., 2002), antisocial behaviors (Criss and Shaw, 2005; Fagan and Najman, 2003), substance use (Fagan and Najman, 2005; Scholte et al., 2008; McGue and Iacono, 2009; Slomkowski, et al., 2005). Furthermore sibling conflicts are as well associated with both internalizing (fear, inhibition, and overcontrol) and externalizing behaviors (aggression, antisocial behavior, and under-control) (Vogt, 2009; Natsuaki et al., 2009; Buist et al., 2013). A number of  studies  have  also  indicated  that  a more discordant sibling relationship is more likely to lead to increases in depressive symptoms and self-harming (Brody, 1998; Richmond, Stocker and Rienks, 2005; Bowes et al., 2014). The above mentioned research outcomes underline the significance of reviewing the relation between the quality of sibling relationship and developmental consequences. Therefore there is an essential need for a measurement tool to evaluate the quality of sibling relationships.

Questionnaire methods and observational methods are the two most featured measurement sources for assessing the quality of the sibling relationship. Observational methods are widely used in the period of early childhood because of the limited availability in collecting self-reports or interview data from such young children (Kramer and Gottman, 1992; Volling et al., 2002). Parent reports of sibling relationship quality are also a common means of assessing sibling relationships in early childhood (Volling and Elins, 1998; Mendelson et al., 1994), but are also used along with children’s self-reports in samples of older children and adolescents (Hetherington et al., 1999; Stocker and McHale, 1992). Due to the growing interest in the sibling relationship and its effects on developmental outcomes during childhood and adolescence, there are now several different questionnaires and scales available to assess sibling relationship quality.  Many of the studies examining the quality of children’s sibling relationships use a measure developed by Furman and Buhrmester (1985) called the Sibling Relationship Questionnaire (SRQ) (Riggio, 2000). This scale was fist adapted to Turkish by Apalaçi (1996) and the second was adapted by Bozbey-Akal?n and Yazgan-?nanç (Bozbey, 2005). Another measure developed by Schaeffer-Edgerton and revised by Mc Hale et al. (1986) is called the Sibling Behavior Rating Scale (SIB) (Ahmeto?lu and Aral, 2008). The scale was adapted to Turkish by Ahmeto?lu and Aral (2008).  Recently, the Adult Sibling Relationship Questionnaire (ASRQ: Stocker et al., 1997); The Lifespan Sibling Relationship Scale (LSRS: Riggio, 2000) and the Brother-Sister Questionnaire (Graham-Bermann and Cutler, 1994) have been developed to assess sibling relationships in late adolescence and early adulthood.  Among the questionnaires and the scales to assess the sibling relationship, the Lifespan Sibling Relationship Scale (LSRS)  by Riggio (2000), is one of the most extensively used self-report tools which has an advantage of comprehensively measuring all aspects of the quality of and attitudes towards sibling relationships during both childhood and adulthood, with established reliability and validity (Riggio, 2000). In addition, this scale has useful characteristics such as short administration time. 

In Turkey there is no measurement tool available in literature for evaluating the quality of sibling relationships of adolescents for both childhood and adolescence periods. The aim of this study is to investigate psychometric properties of the Turkish version of the Lifespan Sibling Relationship Scale (LSRS) and whether it can be used as a tool to measure the quality of adolescent sibling relationships for researches.

Participants

The participants of the study have been selected from four different high schools in the Kar??yaka district of Izmir during the 2013 to 2014 school year using the convenience sampling method. Of the 804 students who participated in the study 52.36% are female (n = 421) whereas 47.64% are male (n = 383) students.  The high school grade distribution shows that 31.23% are 9^th grade (n = 251), 34.70% are 10^th grade (n = 279) and 34.07% are 11^th grade (n = 274) students. The participants are between the ages of 16 and 18.

Instruments

Lifespan Sibling Relationship Scale (LSRS)

The LSRS, developed by Riggio (2000), is a self-report tool that measures one's attitude towards sibling relationships in childhood and adulthood. For consistency, only one sibling was chosen to respond to the questionnaire items (Riggio, 2000).  The degree of agreement or disagreement with 48 statements was rated using a 5-point Likert scale. The LSRS includes 6 subscales, each consisting of 8 items. Subscales of Child Affect and Adult Affect measure emotional aspects in childhood and in adulthood, respectively (love, affection, pleasure, etc.), and subscales of Child Behavior and Adult Behavior measure the degree of interactions through behaviors (phone call, visit, sharing secret, etc.) in their respective stages. Subscales of child cognitions and adult cognitions measure aspects of belief in sibling relationships (closeness and importance of the relationship) in their respective stages. Six subscale scores and the total score are calculated; the higher the score, the more positive attitudes toward sibling relationships. The LSRS has demonstrated internal reliability (alphas range from 0.84 to 0.89, 0.87 to 0.91 and 0.96 for the child, adult and total scales, respectively) and stability (test-retest at the time of norming and in one month yielded correlations greater than 0.80 and 0.91 for the total scale) in responses over time. In the current sample, alphas for the child, adult, and total scales for students were 0.83 to 0.92, 0.88 to 0.90, and 0.96, respectively and 0.87 to 0.88, 0.83 to 0.88, and 0.96, respectively for siblings. Furthermore, the LSRS has been shown to have convergent and discriminant validity with measures of personality, social support, psychological well-being, social desirability, and an alternative measure of adult sibling relationship quality (Jeong et al., 2013)

Before the research was conducted, the permission from the author of the scale (Riggio, H.) was received. For the study, Lifespan Sibling Relationship Scale (LSRS) was first translated into Turkish by the researcher and an English interpreter. Later these translations were checked by three counselors who are proficient in both English and Turkish languages and hold (have) a doctor’s degree at the minimum. The items were finalized utilizing the counselors’ feedbacks. In the next stage,   the pre-final Turkish version and the original English version of the LSRS were administered to 42 prospective English teachers in two sessions separated by an interval of two weeks, and correlations between the two administrations were calculated. The analyses of the psychometric properties of comparison of the Turkish version and the   original  version  of  the  scale  are  reported  in  subsequently.

Personal information form

The information regarding the age, gender and grade of students as well as their birth order, ages of siblings and genders of siblings was collected by a personal information form designed by the researcher.

Procedure

The study was conducted in the classrooms after obtaining permission from the school administrators. Students were informed about the goal of the research and voluntary participation. All of the students volunteered to participate in the study. It took 30 to 35 min for the students to complete the scales. Data collection was undertaken by the author.

Data analysis

Confirmatory factor analysis (CFA) was administered to obtain evidence as to the validity of the structure of the scale. Prior to the test of the structural equation model in the research, a measurement model was created and analyzed, in which the variables which will be included in this structural model are modeled together. Fit and error statistics such as chi square (χ²), χ²/sd, RMSEA, RMR, GFI, AGFI, CFI are taken into consideration while examining the measurement model and the model- data fit. With regard to the statistics calculated, the fact that the value χ²/sd is lower than 5, GFI and AGFI are higher than 0.90, RMR and RMSEA are lower than 0.05 indicates a perfect model -data fit (Hooper et al., 2008). Nevertheless, the fact that GFI is lower than 0.85, AGFI is lower than 0.80, RMR and RMSEA are lower than 0.10 are shown as an acceptable lower bound for model-data fit (Kline, 2005). Additionally, the correlation coefficient was estimated to obtain evidence as to the validity of the language of the scale. To obtain evidence as to the reliability of the instrument, test-retest was evaluated by calculating the correlation coefficient and reliability of internal consistency was evaluated by calculating Cronbach Alpha coefficient and composite reliability coefficient. 

Descriptive statistics prior to the reliability and validity studies of the Lifespan Sibling Relationship Scale (LSRS) are given in Table 1.

The diagram obtained with the confirmatory factor analysis performed in scope of the validity study is given in Figure 1.

The original version of the scale and the version adapted to Turkish were administered at an interval of 2 weeks to a group of 44 persons from the 4th grade students of the department of English teaching at Buca Faculty of Teaching, Dokuz Eylül University in order to determine language validity of the Lifespan Sibling Relationships Scale in the research. The correlation coefficient obtained after two administrations is 0.986.  This indicates that the adapted version of the scale and the original version measure the same structure.

Reliability

The scale was administered to 152 persons twice at an interval of three weeks for test - retest reliability. The correlation coefficient between two scores received by students from the scale was found as 0.966. This value is also an indicator that the scale measured the same individuals at different times consistently.

Cronbach Alpha coefficient and composite reliability coefficient were calculated to determine the reliability of internal consistency of the scale. The internal consistency of the scale was found as 0.95 and composite reliability coefficient as 0.98. Reliability coefficients for the sub-dimensions of the scale are given in Table 2.

As seen in Table 2, reliability values of all dimensions are beyond the acceptable level (Murphy and Davidshofer, 1998). As test - retest values and internal consistency coefficients related to the scale are high; the reliability of the Lifespan Sibling Relationships Scale is accepted to be adequate.

Discussion

The purpose of this study is to adapt the Lifespan Sibling Relationship Scale (LSRS) developed by Riggio (2000) to Turkish. In line with this purpose, the validity of the LSRS is determined by means of studies on structural validity and language validity. As for the reliability of the scale, internal consistency and test-retest reliability coefficients were calculated. The scale consists of six scales in total, including three for adulthood stage and three for childhood stages. The sub-scales for adulthood are "adult affects", "adult behaviors", and "adult cognition". The sub-scales for childhood are "child affects", "child behaviors", and "child cognition".

Confirmatory factor analysis (CFA) was administered to obtain evidence within the scope of the study for the validity of the structure of the scale. This analysis resulted in high scores of goodness of fit. Additionally, the original six factor structure for the scale was verified by means of the CFA performed.   The correlation between the two administrations performed to test the language validity related to the scale was also found high.

The reliability of the LSRS, which consists of 48 items in total, was examined by performing test-retest and internal consistency analyses. The correlation coefficient 0.966 obtained within the scope of test-retest study was considered as an indicator of the reliability of the scale. The internal consistency coefficient obtained as 0.95 from the total of the scale and also the internal consistency coefficients  obtained as 0.811 from adult affects, as 0.78 from adult behaviors, as 0.868 from adult cognition, as 0.822 from child affect, as 0.785 from child behavior and as 0.853 from child cognition. Additionally  composite reliability coefficient obtained as  0.98 from the total of the scale and also the  composite reliability coefficient obtained as 0.91 from adult affects, as 0.87 from adult behaviors, as 0.91 from adult cognition, as 0.84 from child affect, as 0.80 from child behavior and as 0.87 from child cognition constitute another evidence to the reliability of the scale. These results are similar to the results of the original version of the scale as well as those of the Korean version.

The LSRS was examined as to its certain psychometric properties in this study; the findings showed that the instrument is usable. However, this research has some limitations. The participants in this research are adolescents aged from 16 to 18. Sibling relationships are transformed during adolescence to reflect less companionship, less intimacy, less affection and more equality because siblings become more similar in competence and developmental status as they grow up (Updegraff et al., 2002; Buhrmester, 1992; Buhrmester and Furman, 1990). Experiencing such a transition in terms of sibling relationships, this age group can rarely be representative of other age groups. The individuals in the sampling consist of only the students studying at the schools in Kar??yaka district of Izmir. More extensive level of information can be obtained regarding the LSRS if sampling groups from other schools from a variety of provinces also participate in future studies. Furthermore, we will be able to acquire more information about the scale if an adaptation of the study is applied to the sampling group comprising adults. In addition, discriminant validity studies of the scale have not been performed. Further researches may be required to assess the validity of the Turkish adaptation of the LSRS in future.

Sibling relationship as a subsystem within the family system is probably the longest relationship in human life. Siblings are also the most important sources of social support for each other. Therefore, the quality of sibling relationships must be taken into consideration in developmental terms.  This reveals the fact that the LSRS is a functional instrument which can be used in prospective studies on adolescents for assessing the sibling relationships in Turkey. The results reveal that the six-factor structure on adolescents is verified in Turkey, and shows that the scale can be used in relevant researches to be conducted. The literature in Turkey mainly includes studies on relationships of individuals with disabled siblings (Ahmeto?lu, 2004; Aksoy and Berçin-Y?ld?r?m, 2008; Bozbey-Akal?n, 2005; Onat-Zoylan, 2005; Atasoy, 2002; Erden and Akçak?n, 2001; Apalaçi, 1996; Küçüker, 1997; Girli, 1995). However, no studies are available to examine the quality and the psychosocial consequences of sibling relationships of adolescents who have experienced normal development. Therefore, it can be recommended that sibling relationships in Turkish culture should be examined with respect to various age groups and different variables. The relation between sibling relationships and their psychosocial outcomes should as well be subject to research. Furthermore, developmental results of sibling relationships can be examined through longitudinal studies. Additionally, studies on the relation between sibling relationships and family relationships and parenthood styles can as well be recommended.

The author has not declared any conflict of interests.