Many factors, such as early style of parenting, level of effortful control, early peer victimization, parental SES, cultural norms, early play preference, early self-defining memories, as well as early social and academic competence play varying roles in the development of children's personality as typically introverted or extroverted.
      All forms of behavior can be classified into two separate, distinct categories: introverted and extroverted behavior. Extroversion is typically defined as an accommodating, outgoing, easily adaptable and trusting form of behavior, while introversion is typically defined as a reflective, not easily trusting, hesitant and defensive form of behavior (Monte & Sollod, 2003, p142). Carl Gustav Jung was the first psychoanalyst to originate and distinguish between the different attitude types of observable behaviors and went on to further sub classify introversion and extroversion into the functional forms of sensation, intuition, thinking, and feeling. Hence, the two attitude types are not merely rigidly defined, but have room for variation within them (Monte & Sollod, 2003, p142).
      Further sub classifying introversion and extroversion, the ectopsychic functions, as they are termed, can be split up into four categories: sensation, intuition, thinking and feeling. The sensation function focuses on an orientation to reality through the bodily senses. That is, someone who is defined as an extrovert sensation type interprets the external world via his/her senses and comes to the realization that a person or object simply is (Monte & Sollod, 2003, p143). The thinking function complements the sensation function, and acts to link together related concepts in order to come up with a broader definition. The thinking function tells us what an object is (Monte & Sollod, 2003, p143). The feeling function provides us with the value of external or internal stimuli, and finally, the intuition function helps us problem solve in situations that are unfamiliar or new to us in an unconscious manner (Monte & Sollod, 2003, p143).
      Dependant on the amount of logic, reasoning and judgment involved, the ectopsychic functions can be further classified as rational or irrational (Monte & Sollod, 2003, p143). Rationality refers to rational behavior and can be defined by using the ability to reason, while irrationality relates to irrational behavior and can be defined as not being endowed with, or not using, logical and/or reasoning skills. The functions of sensation and intuition can be classified as irrational due to the lack of conscious reasoning involved (Monte & Sollod, 2003, p143). In contrast, the functions of feeling and thinking are classified as rational because of the amount of conscious reasoning involved in those processes (Monte & Sollod, 2003, p143).
      It is a widely accepted notion that extroverts are typically concerned with external stimuli, their social surroundings, and are more assertive (Baron & Byrne, 2004, p557) whereas introverts are concerned more with their subjective experience (Monte & Sollod, 2003, p145). Because introverts are more concerned with their subjective experience, it can be inferred that introverts are typically more prone to anxiety than their extroverted counterparts. Indeed, this is due to the personal exploration of their subjective landscape; that is, the pre-occupation with one's own personal beliefs, ideas, emotions and attitudes. For introverts, this tendency to explore their subjective landscape and to worry about others' perceptions of them makes introverts pre-occupied, anxious and reticent in social situations. However, research by Pontari and Schlenker (2000) found that when introverts were asked to remember an eight-digit number, the cognitive distraction improved their ability to appear extroverted, to better present themselves, and to reduce anxious feelings (Baron & Byrne, 2004, p71). In contrast, when extroverts were asked to remember an eight-digit number, it interfered with their ability to present themselves as shy and withdrawn introverts (Baron & Byrne, 2004, p71). Thus, although at times an overlap between extroverted and introverted behavior can occur where an introvert may present themselves as an extrovert by displaying extroverted behavior, or vice-versa, when introverts appear to be extroverted, personalities are characterized as being mainly introverted, or mainly extroverted.
      Across both genders, a significant level of social competence and pro-social behavior generally leads to the development of a more extroverted personality, while a lack of social competence and prosocial behavior leads to the development of a more introverted personality. Social competence refers to one's ability to adequately adapt or respond to social stimuli in an appropriate manner, while pro-social behavior occurs in a social context and refers to communicating with others in an engaging manner. Research findings have reported that children who are anxious and do not engage in pro-social behavior or activities will develop a more solitary, withdrawn, or introverted behavior orientation (Gazelle & Rudolph, 2004). Yet, apart from the Jungian sub classification of the attitude types, it has been recently noted that other forms of introversion exist. Introverted shyness is a state in which a child prefers to be alone, yet can be an effective participant in social interactions if and when prompted, while conflicted shyness is a state wherein a child desires to engage in social activities, but due to social fear or anxiety, does not do so (Coplan, Prakash, O'Neil, & Armer, 2004). Thus, it can be inferred that if introverted or conflicted shyness were to persist throughout adolescence, those children will develop a more introverted behavior orientation, whereas those who persistently engage in pro-social behaviors and show a high degree of social competence will develop a more extroverted behavior orientation.
      Another determinant of introversion or extroversion is style of parenting, and there exist two significant types: authoritative and authoritarian (Coplan, Prakash, O'Neil, & Armer, 2004). An authoritative parenting style is one that is characterized by maternal warmth, responsivity, and firm boundary setting, and is related to greater social competence, while authoritarian parenting style is harsher, coercive, and strict and is linked to social isolation and withdrawal (Coplan, Prakash, O'Neil, & Armer, 2004). Generally, authoritative parenting leads to greater levels of extroversion, while authoritarian parenting predicts greater levels of introversion (Coplan, Prakash, O'Neil, & Armer, 2004).
      For girls, their personality development will lean towards a more extroverted one in the case that their parents raised them in an authoritative style. In a study done by Diener & Kim (2004) in which the researchers sought to determine the cumulative effect of maternal behavior towards their children, children's characteristics (temperament and self-regulation), and whether a child is familiar with at least one classmate upon later social competence, it was found that correlations existed between girls' pro-social or withdrawn behavior and their parent's style of parenting. Participants for the study included one hundred ten children (43% female) and their mothers. The mothers were asked to complete a survey to assess child temperament and self-regulation, maternal separation anxiety, and other demographic information. To assess the mothers' perceptions of children's temperament and self-regulation, the mothers were asked to complete the Children's Behavior Questionnaire. Maternal separation anxiety was measured by asking the mothers to complete the Maternal Separation Anxiety Scale. Mothers were sent a roster of their child's classmates and were asked to answer yes or no if their child knew any other child in the class. Children's social competence in the classroom was assessed by the teacher or assistant teacher using Cassidy and Asher's Teacher Questionnaire in which children were rated on three different behavioral aspects. To control for the mothers' intervention in the classroom, mothers were observed while supervising an activity that forced them to intervene in some way (Diener & Kim, 2004). The results showed that positive maternal support (authoritative parenting) correlated positively with girls' pro-social behaviors (r = .20), whereas negative maternal support (authoritarian parenting) correlated negatively with girls' withdrawn behaviors (r = - .19). Thus, for girls, it seems as if a warmer, authoritative parenting style leads to higher levels of social competence and a higher degree of extroversion.
      For boys, their behavior orientation will be predicted as extroverted in part by their parents' style of parenting, but more so than for girls. A study done by Coplan et. al. (2004) helps to further this notion. In their study, the investigators attempted to distinguish between conflicted shyness and social disinterest and to determine whether or not there was a correlation between both of the above mentioned variables as well as other possible factors that may have influenced a child's social development. Participants for this study included two groups. Group one consisted of 119 children (55 boys, 64 girls), while group two consisted of 127 children (68 boys and 59 girls). Observations were taken six months into the preschool year by six trained research assistants for group one when children were given a forty-five to sixty minute lunch break. Each child in the group was observed for a series of ten second intervals for two to three minutes. This procedure was repeated until each observer had observed their assigned children on four separate days. Teachers in the first group were asked to complete the Child Behavior Scale to assess preschool children's adjustment with other peers. To assess parenting styles, Mothers in the second group filled out the Parenting Styles and Dimensions Questionnaire. In order to assess the importance that parents place on children's sociability and peer relations, the Mothers in group two also completed the Revised Social Goals Inventory. Child perceived competence and play choice were also measured (Coplan, Prakash, O'Neil, & Armer, 2004). The results from the study showed that for both genders, maternal over protectiveness was significantly and positively related to conflicted shyness, while authoritative parenting was significantly and negatively correlated to conflicted shyness. Yet while maternal over protectiveness was significantly and positively correlated to conflicted shyness or introversion for boys (r = .33), there was no significant relation for girls (r = .03). In addition, results from another study have shown that positive maternal warmth positively correlates with pro-social behavior for boys (r=.17) (Diener & Kim, 2004). Indeed, for boys, as well as for girls, an authoritative parenting style is positively related to pro-social behavior, and thus influences the development of an extroverted personality.
      Effortful control is another factor that relates to the development of a child's behavior as introverted or extroverted. Effortful control refers to one's ability to self-regulate emotions, the efficiency of attention to stimuli, and also includes one's ability to restrict dominant responses (Fabes, Martin, Hanish, Anders, & Madden-Derdich, 2003). Results from a study done by Fabes et. al. (2003) in which the focus was to determine whether or not correlations between boys' and girls' levels of effortful control and their perceived levels of academic, social and perceptual-motor competence existed showed that the mean for effortful control of girls was .14 (SD = 1.03), whereas the mean for effortful control of boys was found to be -.14 (SD = .90). Participants for that study included 98 children (50 boys and 48 girls) with a mean age of 55.56 months and 53.94 months, respectively. Two observers coded observations of children during both outdoor and indoor free-play with a focus on whether the child was participating in same-sex or mixed sex interaction. To measure effortful control, assistant teachers completed a variation of the Attention Shifting, Attentional Focusing and Inhibitory Control Subscale from the Children's Behavior Questionnaire. To assess temperament, teachers were paid five dollars per child to complete questionnaires developed from standard assessment protocols. Academic competence was measured using a nine-item scale that measured mathematical abilities and logical thinking, social competence was assessed with a six-item scale that asked questions about a child's level of socially appropriate behavior at school, while perceptual-motor competence was measured using a five-item scale assessing locomotor, perceptual, and physical skills.
      In another study conducted by Zhou et. al. (2004) in which the relationship between parenting style, dispositional anger/frustration and level of effortful control to Chinese children's social functioning was examined, it was found that teachers rated girls as higher in effortful control (M = .30) than they rated boys (M = -.38). In that study, participants included 425 first and second grade children recruited at schools in Beijing. Parenting style was measured by using the Chinese version of the Parenting Styles and Dimensions Questionnaire. Parents were asked to complete a subset of the Marlowe-Crowne Social Desirability Scale to assess parental social desirability. To measure effortful control, two subscales of the Chinese version of Rothbart's CBQ were used. Dispositional anger/frustration was measured using the anger/frustration subscale of the CBQ. Parents and teachers were both asked to complete an adapted version of Harter's Perceived Competence Scale for Children to assess children's socially appropriate behavior and externalizing problems. Peer assessments of social behavior were also taken using a Chinese version of the Revised Class Play (Zhou, Eisenberg, Wang, & Reiser, 2004). Previous studies have noted that higher levels of effortful control lead to a greater degree of sociability, social competence and extroversion, but are needed more so for boys than for girls because boys engage in more physical and active types of play and those more easily dysregulated may be at greater risk for poorer social competence (Fabes, Martin, Hanish, Anders, & Madden-Derdich, 2003).
      Girls will develop a more extroverted personality if they show high levels of effortful control. The aforementioned study done by Fabes et. al. (2003) showed that the mean for effortful control of girls was found to be .14 (SD = 1.03) whereas the mean for effortful control of boys was found to be -.14 (SD = .90). Therefore, girls showed a greater degree of effortful control than did boys. A positive correlation was found between girls' level of effortful control and their social competence (r=.51) as well as between effortful control and academic competence (r=.47) (Fabes, Martin, Hanish, Anders, & Madden-Derdich, 2003). Results from another study showed that parents' ratings of their children's social functioning and of their children's effortful control were positively correlated (r=.49) (Zhou, Eisenberg, Wang, & Reiser, 2004). Both studies found that high levels of effortful control predicted social and academic competence, which in turn relate to the development of a personality type.
      Boys with a higher level of effortful control will develop a more extroverted personality type than boys with a lower level of effortful control. It has been suggested in recent studies that boys need a higher level of effortful control to compensate for their styles of peer interaction and peer play. That is, because boys are more easily dysregulated and engage in more aggressive types of peer play, they will need a higher level of effortful control than will girls for social and academic competence (Fabes, Martin, Hanish, Anders, & Madden-Derdich, 2003). Thus, boys with a higher level of effortful control will have more social and academic competence, as well as a more extroverted personality. The study done by Fabes et. al. (2003) showed that a positive correlation was found between effortful control and social and academic competence (r = .19, r = .32, respectively). Another study found that parents' ratings of effortful control for boys (M=4.58, SD=.56) was lower than parents' ratings of effortful control for girls (M=4.75, SD=.64); in addition, parents' ratings of their child's social functioning was lower for boys (M= -.16, SD=.83) than for girls (M=.11, SD=.84), once again indicating that effortful control is positively correlated to social functioning (Zhou, Eisenberg, Wang, & Reiser, 2004), and that the higher the level of effortful control, the higher the probability that a child's personality will develop into an extroverted one.
      Peer victimization is another contributing factor to the development of extroverted or introverted personality types, although unlike effortful control and parenting style, the overall affect of peer victimization on personality development does not differ across genders. Peer relationships have the ability to hinder and/or improve a child's psychological or social development (Ladd & Troop-Gordon, 2003). A study done by Snyder et. al. (2003) helps to further this notion. Snyder et. al. sought to study the rate of peer victimization, as well as its causes and effects, over a two year period. Participants included 132 girls and 134 boys with a mean age of 5.5 years (range = 5.2 - 6.1). Playground observations were taken for five minutes (30 ten second intervals) by two trained observers who used inter-rater reliability to assess agreement. To measure overt antisocial and depressive behavior in the classroom, teachers were asked to complete the Teacher Report Form, parents were asked to complete an adaptation of the Child Behavior Checklist, and the children were asked to give a self-report to obtain a measure of the depressive affect and behavior at the end of first grade (Snyder, Brooker, Patrick, Renee, Snyder, Schrepferman, & Stoolmiller, 2003). Results from this study showed that peer victimization for both genders correlated positively with teacher reported antisocial behavior. For boys, the correlation between peer victimization and teachers' ratings of antisocial behavior was found to be .28 (r=.28), while for girls, the correlation between peer victimization and teachers' ratings of antisocial behavior was found to be .24 (r=.24). However, no significant correlations were found between peer victimization and children's depressive symptoms for boys or girls (r=.09, r=.01, respectively). From the aforementioned results, it can be deduced that the persistence of peer victimization relates to, and predicts antisocial behavior, which in turn affects the development of personality.
      For both genders, chronic peer rejection contributes to the development of a more introverted personality type. Negative environmental responses have been known to reinforce maladaptive social predispositions, thus aiding in the persistence of maladaptive behavior (Gazelle & Rudolph, 2004). The results from a study done by Ladd & Gordon (2003) in which the investigators sought to examine the causes and consequences of chronic peer adversity in early childhood showed a correlation between chronic peer rejection and loneliness. Participants included 193 girls and 206 boys with a mean age of 5.5 years. Teachers were asked to rate child behaviors using the Child Behavior Scale. Children rated their acceptance or rejection of classmates and themselves using a rating scale of peer acceptance. Peer victimization was assessed by asking the children to complete a two-item peer nomination measure. In addition, interviews were conducted when the children were in first and second grade to assess peer acceptance, victimization and friendship variables (Ladd & Gordon, 2003). Across both genders, the results showed that peer victimization and internalizing problems correlated positively (r=.17), and that peer rejection and internalizing problems correlated positively (r=.20). By definition, introverts internalize problems and focus more on the subjective experience, thus according to the data, if chronic peer rejection and victimization were to persist, so would the internalization of problems. Therefore, the persistence of chronic peer adversity relates to, and predicts, the development of an introverted personality type for both genders.
      In contrast, youth who are not rejected by peers but display characteristics of introversion such as anxiety and solitude have the potential to increase positive pro-social behaviors or in some cases, to develop into an extrovert later in life. In the absence of peer rejection, victimization or exclusion, positive environmental responses can lessen the degree of maladaptive social pre-dispositions and maladaptive behavior (Gazelle & Rudolph, 2004). Gazelle & Rudolph (2004) investigated the relationship between anxious solitary excluded youth, versus anxious solitary non-excluded youth in order to determine if overall social functioning improved or declined over time. Participants for the study included 519 fifth and sixth grade children from a Midwestern community. Anxious solitude was measured by asking the children's teachers to complete both the Teacher's Report Form and the Child Behavior Scale. Peer exclusion was assessed using the information obtained from the CBS. Aggressive and prosocial behavior were measured using the Teacher Assessment of Social Behavior. Social helplessness was measured using the Social Helplessness Scale. Depressive symptoms were measured using the Children's Depression Inventory. Dependant upon the results from these measures, participants were divided into two groups: high anxious solitary excluded, and high anxious solitary nonexcluded (Gazelle & Rudolph, 2004). Correlational and descriptive statistics for that study were not computed, however, results showed that for the high anxious solitary excluded group, pro-social behavior declined over time, indicating a negative correlation between peer exclusion and pro-social behavior (Gazelle & Rudolph, 2004). When peer exclusion did not persist, high anxious solitary youth showed a steady incline in pro-social, adaptive behaviors over time, indicating a negative correlation between peer exclusion and pro-social behavior (Gazelle & Rudolph, 2004). Although peer rejection and pro-social behavior correlate negatively, in the absence of peer rejection, introverted youth have the potential to improve their social functioning, social skills and pro-social behaviors over time, and in some cases, to develop an extroverted personality type.
      Parental socioeconomic status (SES) is a factor that plays an indirect role in the development of a child's personality as more extroverted. A study done by Cohen et. al. (2003) sought to examine the transitional phase from adolescence to adulthood, demographic variations in the transition from age 17 to age 27, as well as transitional markers and the influences of the process of separation, independence and autonomy. Participants included 240 members of the Children in the Community (CIC) cohort. When these participants ranged in age from one to 10 years, their mothers were interviewed about a wide range of demographic questions and individual characteristics of the target child. Family SES was measured based upon the early interviews with the mothers. The results from the study showed that parental SES and school attendance were positively correlated. For participants whose parents had a high SES (n=113), the mean value of those attending school was found to be 16.5, whereas of the 127 participants in the low SES group, the mean value of those attending school was 8.8 (Cohen, Kasen, Chen, Hartmark, & Gordon, 2003). In the aforementioned study by Fabes et. al. (2003), it was found that effortful control correlated positively with academic competence (r = .32) and thus predicted a greater degree of extroversion for those high in effortful control or academic competence. Since parental SES and school attendance correlate positively, and academic competence and degree of extroversion correlate positively, there is a small, indirect and positive relationship between parental SES and degree of extroversion.
      Parental SES also plays an indirect role in the development of a youth's personality as more introverted. A study done by Cohen et. al. (2003) helps to further this notion. In their study, 200 participants were selected and interviewed about where they lived, worked and studied as well as the dates of significant experiences that may have occurred such as marriages, divorces, graduations, illnesses, births, and special achievements. The interview covered the areas of residence, finance, school, employment, romance and parenting. Results from their analyses showed that participants who came from higher SES backgrounds were slower to assume romantic and sexual involvement, and parenting (45.1% vs. 31.5%, respectively), therefore by definition, participants from higher SES backgrounds displayed indirectly a higher degree of introversion than participants who came from lower SES backgrounds (Cohen, Kasen, Chen, Hartmark, & Gordon, 2003).
      Another study conducted by Rutter et. al. (2004) in which the researchers investigated the hypothesis that permanent cognitive and/or physical effects may exist in children reared in depriving institutions due to early unfavorable experiences showed a relationship between parental SES and the development of an introverted personality type. Participants for the study included 324 children reared in Romanian institutions who were later adopted into UK families. A comparison sample used 52 UK-born children adopted into families before the age of six months. Children were assessed on weight and head circumference at the ages of 4 and 6. The Revised Denver Prescreening Developmental Questionnaire measured the level of the participants' developmental progress. Participants were interviewed at ages four and six to measure developmental progress and disinhibited attachment disturbances. In addition, the McCarthy Scales of Children's Abilities was used to assess standard cognitive and developmental progress (Rutter, O'Conner, & the English and Romanian Adoptees Study Team, 2004). Results indicated marked cognitive impairments in 15.4% of children who experienced institutional deprivation in comparison to a 2% cognitive impairment for the within-UK adoptee group. For those who spent six months or less in the depriving institutions, there was a 2.3% cognitive impairment, and a 32% cognitive impairment for participants who spent anywhere from 24 to 42 months in the institution. After leaving the institutions, catch-up in weight--but not in head-circumference--was nearly complete by six years of age between the two groups. The lack in catch-up in head circumference can be attributed to malnutrition. Finally, rate of disinhibited attachment for those who experienced less than 18 months in the institution was 16% whereas disinhibited attachment for those who experience lasted between 24 and 42 months was 33% (Rutter, O'Conner, & the English and Romanian Adoptees Study Team, 2004). These results indicate that children who come from a low SES background may not get the adequate nutritional needs necessary for proper cognitive development and have the potential to develop into maladjusted introverts if nutritional deprivation were to persist.
      Cultural norms play a role in the development of children's personality type. A culture is a group of people who share the same set of values, beliefs and interpretations (Baron & Byrne, 2004, p12). Cultural norms refer to the appropriate or expected behavioral orientation or social rules of a given society and are reflected in the way in which people act. In relation to Jungian archetypes, cultural norms can be classified under the Mother archetype, which includes both the angry and loving mother (Monte & Sollod, 2003, p136). Social norms and rules can either be classified as the authoritarian or authoritative mother figure: harsh, strict and coercive, or warm, responsive and democratic, thus affecting the development of personality accordingly. Results from the previously mentioned study by Zhou et. al. (2004) help to further the notion that cultural norms affect the way in which we act, hence influencing personality type.
      The differences between parent and teacher ratings of children's levels of effortful control found in the study conducted by Zhou et. al. (2004) imply an influence of China's cultural norms on social behavior. In the Zhou et. al. study (2004), parents rated their children higher in effortful control than did teachers. The mean of teacher reports for girls' effortful control was found to be 5.17 (SD=.92), while the parent reported mean for girls' effortful control was 4.75 (SD=.64). The difference between parent and teacher ratings of girls' effortful control may be potentially due to children's tendency to display more reticent behavior in a classroom environment in part due to China's cultural norms.       If cultural norms relate more closely to an authoritarian mother archetype, then the development of children's personality type may lean more towards the introverted side, whereas if cultural norms relate more closely to an authoritative mother archetype, then the development of children's behavior may lean more closely towards the extroverted type as seen by previously reported results on the influence of parenting style to personality type. In the study conducted by Zhou et. al. (2004), the mean number of girls who came from a home in which an authoritative parenting style was used was 3.78 (SD=.53), whereas the mean number of girls who came from a home in which an authoritarian parenting style was used was 2.27 (SD=.42). Similarly, more boys were reared in a home in which an authoritative parenting style was used (M=3.73, SD=.51) than were boys reared in a home in which an authoritarian parenting style was used (M=2.34, SD=.51) (Zhou, Eisenberg, Wang, & Reiser, 2004). According to the data it can be inferred that China's cultural norms reflect an authoritative mother archetype and thus stimulates the development of a more extroverted personality type in its youth.
      Early play preference is another factor that plays a role in the development of children's personality type. Early play preference refers to the style of peer interaction in which children typically engage and includes same-sex peer play, mixed-sex peer play, and social disinterest. Social disinterest is characterized by little to no motivation to play with peers, and instead to play alone or with a teacher (Coplan, Prakash, O'Neil, & Armer, 2004). Across both genders, social disinterest in children encourages the development of a more introverted personality type, while pro-social behavior with peers promotes the development of a more extroverted personality type.
      Early solitary-passive play, as well as reticent behaviors have a tendency to influence the development of a more introverted personality type. The study done by Coplan et. al. (2004) shows a negative correlation between solitary-passive play and pro-social behavior with peers across both genders (r = -.13), and a less significant negative correlation between reticent behavior and pro-social behavior (r = -.07). However, no significant correlation was found between perceived competence and social disinterest (r = -.05) (Coplan, Prakash, O'Neil, & Armer, 2004). By definition, introverts display more reticent forms of behavior, thus if social disinterest or the preference to engage in less pro-social activities were to persist, a more introverted personality type would be apparent in those children.
      The tendency to engage in same-sex peer play versus mixed-sex peer play plays a role in the development of personality type, where mixed-sex play for girls predicts a greater degree of extroversion and same-sex peer-play for boys predicts a great degree of extroversion (Fabes, Martin, Hanish, Anders, & Madden-Derdich, 2003). In contrast, a greater degree of same-sex peer interactions for girls fosters the development of a more introverted personality type, while a greater degree of mixed-sex peer interactions for boys fosters the development of a more introverted personality type. On the topic of early school competence, it has been noted in the literature that boys' and girls' peer group interactions appear to influence distinct behavioral orientations and rules (Fabes, Martin, Hanish, Anders, & Madden-Derdich, 2003). Results from a study on early school competence show a small negative correlation between girls' social school competence and level of same-sex peer play (r = -.11), but a positive correlation between girls' social school competence and level of mixed-sex play (r = .15), whereas for boys the converse was apparent (Fabes, Martin, Hanish, Anders, & Madden-Derdich, 2003). A significant positive correlation was found between boys' social school competence and same-sex peer play (r=.25), while a negative correlation was found between boys' social school competence and mixed-sex peer play (r = -.13) (Fabes, Martin, Hanish, Anders, & Madden-Derdich, 2003). From the data, it can be deduced that boys who engage in more same-sex peer interactions early on will develop a more extroverted personality type; boys who engage in more mixed-sex peer interactions early on will develop a more introverted personality type; for girls, early mixed-sex peer interactions seem to foster the development of a more extroverted personality type while early same-sex peer interactions appear to promote the development of a more introverted personality type.
      Although same-sex peer interactions promotes the development of a more extroverted personality in boys, effortful control plays a mediating role between same-sex peer interaction and social school competence. In the previously mentioned study by Fabes et. al. (2003), a positive correlation was found for boys high in effortful control between social interactions in same-sex peer groups and social competence (r=.46), while a negative correlation was found for boys low in effortful control between social interactions in same-sex peer groups and social competence (r = -.46). So albeit same-sex play for boys is a good predictor of extroversion, a high level of effortful control mediates the relationship between social school competence and same-sex peer interactions, and thus, boys high in effortful control who engage in same-sex peer groups have the potential to develop a more introverted personality type.
      Early self-defining memories have the ability to influence personality development. A self-defining memory is typically vivid, providing a person with insight or a life lesson and generally focuses on the themes of closeness, separation or conflict (McLean & Thorne, 2003). In that study, the researchers sought to observe what meaning late adolescents assigned to vivid memories, to investigate peer memories, memories with parents, as well as the association between interpersonal conflict and meaning-making. Participants for the study included 203 undergraduate students who were asked to report at least one self-defining memory where the central theme involved another person. The participants were then asked to complete a four page questionnaire asking for demographic information and to report one self-defining memory. The data was then coded into six separate categories: relationship memories, conflict, separation, closeness, lesson learning and gaining insight (McLean & Thorne, 2003). As previously mentioned, two studies have found that girls have a higher rating of social school competence or overall social functioning than do boys (Fabes, Martin, Hannish, Anders, & Madden-Derdich, 2003; Zhou, Eisenberg, Wang, & Resier, 2004), and thus by definition, display a higher degree of extroversion. Similarly, the results from the McLean & Thorne (2003) study showed a tendency for females (M=.83, SD=.79) to report a higher percentage of closeness memories than did males (M=.58, SD=.77). It can be deduced that females either experience more early closeness memories than do males or report more early closeness memories than do males. Nevertheless, females focused more on the theme of closeness in their memories as well as in their lives than did males, fostering the development of a more extroverted personality type and providing insight as to the reason why a greater degree of females than males are extroverts.
      Factors such as early self-defining memories, early play preference, cultural norms, parental SES, degree of peer victimization, level of effortful control, and early parenting style all play varying roles in the development of a child's personality type. Two categories of personality types exist: introversion and extroversion. Introversion is defined as the tendency to explore and focus on one's own subjective landscape and others' perceptions and is characterized by shyness, hesitancy, social withdrawal or anxiety. Introverts are more reflective and defensive than their extroverted counterparts (Monte & Sollod, 2003, p142). Extroversion is defined as the tendency to be charismatic, out-going and assertive and is characterized by having little difficulty in adapting to unfamiliar environments as well as having a greater degree of pro-social behavior, social competence, and social functioning (Monte & Sollod, 2003, p142). Many different factors play varying roles in the development of children's personality development, and each factor influences personality development differently; the different relationships between extroversion and introversion and early self-defining memories, early play preference, cultural norms, parental SES, degree of peer victimization, level of effortful control, and early parenting style result in the development of a mainly introverted personality type, or a mainly extroverted personality type.
      Parenting style was one factor influencing the development of personality, and the two types of parenting style affect personality development differently. Across both genders, an authoritative parenting style, which is characterized by warmth, responsiveness and firm boundary setting, fosters the development of a more extroverted personality type, but more so for boys than for girls. An authoritarian parenting style, which is characterized as coercive, harsh and strict, influences the development of an introverted personality type for both genders (Coplan, Prakash, O'Neil, & Armer, 2004). Three studies provide an empirical background for the notion that an authoritative parenting style predicts the development of an extroverted personality type, and the converse, that authoritarian parenting nurtures the development of an introverted personality type (Diener & Kim, 2004; Coplan, Prakash, O'Neil, & Armer, 2004; Zhou, Eisenberg, Wang, & Resier, 2004).
      It was also suggested that cultural norms reflect the Jungian mother archetype and therefore influence personality development appropriately. A culture is defined as a group of people who have the same beliefs, values and perceptions (Baron & Byrne, 2004, p12). Cultural norms refer to the appropriate or expected behavioral orientation or social rules of a given society and are reflected in the way in which people act. In addition, cultural norms affect the manner in which a person behaves in any given environment. If cultural norms reflect a more authoritarian (angry) mother figure, then cultural norms may play a role in the development of an introverted personality type, whereas if cultural norms reflect a more authoritative (warm) mother archetype, the rules and norms may influence the development of a more extroverted personality type, as was found in the study by Zhou et. al. (2003) in which Chinese children's effortful control and dispositional anger/frustration were examined in relation to style of parenting and social functioning.
      Effortful control was found to play a varying role in the development of personality and refers to the effectiveness of executive attention, encompassing the ability to restrict a dominant response and to execute a subdominant response in its stead, as well as the ability to detect or predict errors (Fabes, Martin, Hannish, Anders, & Madden-Derdich, 2003). In two of the aforementioned studies, a higher level of effortful control was found for girls than boys and correlated positively with overall social functioning or social competence (Zhou, Eisenberg, Wang, & Resier, 2004; Fabes, Martin, Hanish, Anders, & Madden-Derdich, 2003). Effortful control was found to play a mediating role between dispositional anger/frustration and social functioning; a positive correlation was found between boys high in both dispositional anger/frustration and effortful control and social functioning (Zhou, Eisenberg, Wang, & Resier, 2004). Similarly, although same-sex peer interactions influences the development of a more introverted personality in boys, effortful control was found to play a mediating role between same-sex peer interaction and social school competence (Fabes, Martin, Hannish, Anders, & Madden-Derdich, 2003). Across both genders, a higher level of effortful control fosters the development of an extroverted personality type, while lower levels of effortful control predict the development of an introverted personality type.
      Degree of peer adversity was another factor influencing the development of personality type equally across both genders. Peer adversity can be sub classified into the categories of peer exclusion, peer rejection and peer victimization (verbal and/or physical abuse). These different kinds of negative environmental responses have been known to reinforce maladaptive social predispositions and thus maladaptive social behaviors (Gazelle & Rudolph, 2004). Three previously mentioned studies support the notion that if peer adversity persists, the development of a shy, withdrawn, lonely, antisocial, solitary, or introverted personality type would be encouraged (Ladd & Troop-Gordon, 2003; Snyder, Brooker, Patrick, Snyder, Schrepferman, & Stoolmiller, 2003; Gazelle & Rudolph, 2004).
      Parental socioeconomic status (SES) was found to play a small and indirect role in the development of a personality type. According to the previously mentioned study by Cohen et. al. (2003), parental SES and school attendance were positively correlated, and thus was found to be indirectly and positively correlated with school social and academic competence. In addition, results from a study by Rutter et. al. (2004) implied that children reared in depriving institutions may be slower to develop cognitively, thus indicating that a lower parental SES has the potential to foster a more introverted personality type. However, in contrast, results from the study done by Cohen et. al. (2003) showed that participants who came from higher SES backgrounds were slower to assume romantic and sexual involvement, and parenting, therefore displaying indirectly a higher degree of introversion than participants who came from lower SES backgrounds (Cohen, Kasen, Chen, Hartmark, & Gordon, 2003). Future studies may want to examine the affect(s), if any, parental SES has on the development of personality type.
      As mentioned earlier, early play preference encompasses same-sex play, mixed-sex play, solitary-passive play and social disinterest and affects the development of personality type. Fabes et. al. (2003) investigated the roles of sex-segregated play and effortful control on early school competence. Findings from that study show that for boys, mixed-sex peer play correlated positively with pro-social behavior, while same-sex peer play correlated positively with pro-social behavior for girls. Therefore, mixed-sex peer play influences the development of an extroverted personality type for boys, while same-sex play influences the development of an introverted personality type for girls. If solitary-passive play, reticent behaviors and social disinterest persist, then the development of an introverted personality is encouraged, but in the case that children increasingly engage in pro-social behavior and reduce the frequency of solitary activity, there is the potential to develop a more extroverted personality. Similarly, if boys engage in more mixed-sex peer play, there is the potential to develop a more extroverted personality type.
      Early self-defining memories were found to play a slight role in the development of personality and refer to vivid memories in which the themes of separation, closeness or conflict were the focus (McLean & Thorne, 2003). In the aforementioned study by McLean & Thorne (2003), the results showed that females reported more closeness memories than did males, implying a greater degree of extroversion whether through experiencing more incidences in which closeness was the theme during their childhood or simply through reporting more closeness memories than did males. Further studies in the topic of self-defining memories may want to investigate the implications that early self-defining memories have on personality development.
      A consistent finding across most studies was that females displayed more pro-social and extroverted behavior than did males, thus fostering the development of a more extroverted personality type more so for females than for males. However, there was no empirical data to differentiate between the varying degrees to which the different factors examined play in the development of personality type. Differences between the varying degrees to which the factors examined play in the development of personality type may be attributable to genetic and evolutionary predispositions as well as cultural norms. For example, effortful control may play more of a determining factor in the development of personality type than parental SES due to cultural norms, or parenting style may play more of a determining factor than effortful control due to genetic and evolutionary predispositions and the notion of archetypes, although there was no data to support that notion; the degree to which one factor plays in the development of a personality type is unknown. Overall, many different factors contribute to the development of a personality type, but no cause and effect relationships were found to support this notion, therefore, for instance, it cannot be stated that an authoritative parenting style always leads to the development of an extroverted personality or that a high level of effortful control for boys always leads to the development of an extroverted personality type, but all of the examined factors together play a combined role in the development of personality types.