Predictors of academic achievement and social competence in adolescence : facilitation, inhibition and general cognitive processing /

The relevance of attentional measures to cognitive and social adaptive behaviour was examined in an adolescent sample. Unlike previous research, the influence of both inhibitory and facilitory aspects of attention were studied. In addition, contributions made by these attentional processes were compared with traditional psychometric measures of cognitive functioning. Data were gathered from 36 grade 10 and 1 1 high school students (20 male and 16 female students) with a variety of learning and attentional difficulties. Data collection was conducted in the course of two testing sessions. In the first session, students completed questionnaires regarding their medical history, and everyday behaviours (the Brock Adaptive Functioning Questionnaire), along with non-verbal problem solving tasks and motor speed tasks. In the second session, students performed working memory measures and computer-administered tasks assessing inhibitory and facilitory aspects of attention. Grades and teacher-rated measures of cognitive and social impulsivity were also gathered. Results indicate that attentional control has both cognitive and social/emotional implications. Performance on negative priming and facilitation trials from the Flanker task predicted grades in core courses, social functioning measures, and cognitive and social impulsivity ratings. However, beneficial effects for academic and social functioning associated with inhibition were less prevalent in those demonstrating a greater ability to respond to facilitory cues. There was also some evidence that high levels of facilitation were less beneficial to academic performance, and female students were more likely to exceed optimal levels of facilitory processing. Furthermore, lower negative priming was ''S'K 'i\':y-: -'*' - r " j«v ; ''*.' iij^y Inhibition, Facilitation and Social Competence 3 associated with classroom-rated distraction and hyperactivity, but the relationship between inhibition and social aspects of impulsivity was stronger for adolescents with learning or reading problems, and the relationship between inhibition and cognitive impulsivity was stronger for male students. In most cases, attentional measures were predictive of performance outcomes independent of traditional psychometric measures of cognitive functioning. >,, These findings provide support for neuropsychological models linking inhibition to control of interference and arousal, and emphasize the fundamental role of attention in everyday adolescent activities. The findings also warrant further investigation into the ways which inhibitory and facilitory attentional processes interact, and the contextdependent nature of attentional control.associated with classroom-rated distraction and hyperactivity, but the relationship between inhibition and social aspects of impulsivity was stronger for adolescents with learning or reading problems, and the relationship between inhibition and cognitive impulsivity was stronger for male students. In most cases, attentional measures were predictive of performance outcomes independent of traditional psychometric measures of cognitive functioning. >,, These findings provide support for neuropsychological models linking inhibition to control of interference and arousal, and emphasize the fundamental role of attention in everyday adolescent activities. The findings also warrant further investigation into the ways which inhibitory and facilitory attentional processes interact, and the contextdependent nature of attentional control.

Aerobic exercise in adolescence : self-efficacy and stage of change

The purpose of this cross-sectional exploratory study was to examine the relationships among self-efficacy, stage of change, and exercise behaviour in a sample of younger (Grade 9) and older (Grade 12) adolescents. A secondary objective of this study was to apply the transtheoretical model of Stage of Change, as a measure of intention to change, in order to discover the applicability of the model to an adolescent cohort in relation to exercise behaviour. This five-stage model is a self-report measure of an individual's readiness to adopt a new behaviour (e.g., regular exercise). The transtheoretical model incorporates Bandura's self-efficacy factor, which is purported to be a predictive measure of exercise behaviour and a covariant of stage. Exercise behaviour was measured with the Physical Activity Scale, and the University of Rhode Island Change Assessment Scale (URleA) was used to measure the stage of change and self-efficacy variables. The results of this study indicated significant differences between younger and older adolescents, and between males and females in their exercise behaviour. No significant differences were found for grade and gender on stage of change as measured by either a single-item question or a continuous measure of stage. Although grade and gender subgroups were not significantly different in their self-efficacy, significant interaction was found in the grade*gender variable.

Longitudinal associations between passions and adjustment in adolescence: Positive mood and unstructured leisure activities as mediators

Passions are activities that people find important, like or enjoy, and on which they spend large amounts of time. Research examining passions in adolescence has been limited, despite a tendency for adolescents to explore their identity by trying new activities (Dworkin et aI., 2003). The purpose of the present study was to examine the association between adolescent passions and positive adjustment (psychological well-being, optimism, purpose in life, and low risktaking), as well as investigate possible underlying mechanisms for the link between passions and adjustment. High school students (N=2270, 48.7% female) from Southern Ontario completed questionnaires in grades 10, 11, and 12. Path analyses were conducted to examine cross-lag paths among all study variables. Passions predicted higher optimism and purpose, as well as lower negative risk-taking, over time, but these adjustment indicators in tum did not predict higher passions over time. Additionally, positive mood and unstructured leisure activities partially mediated these associations. Passions appears to be important for adolescent adjustment, and may serve as a protective factor or help to foster thriving.

Disambiguating the Effects of Social Instability Stress in Adolescence on Learning and Memory Tasks that Involve the Medial Prefrontal Cortex and Hippocampus

Exposure to chronic stress can alter the structure and function of brain regions involved in learning and memory, and these effects are typically long-lasting if the stress occurs during sensitive periods of development. Until recently, adolescence has received relatively little attention as a sensitive period of development, despite marked changes in behaviour, heightened reactivity to stressors, and cognitive and neural maturation. Therefore, the purpose of the present study was to investigate the long-term effects of chronic stress in adolescence on two spatial learning and memory tasks (Morris water maze and Spatial Object Location test) and on a working memory task (Delayed Alternation task). Male rats were randomly assigned to chronic social instability stress (SS; daily 1 hour isolation and subsequent change of cage partner between postnatal days 30 and 45) or to a no-stress control group (CTL). During acquisition learning in the Morris water maze task, SS rats demonstrated impaired long-term memory for the location of the hidden escape platform compared to CTL rats, although the impairment was only seen after the first day of training. Similarly, SS rats had impaired long-term memory in the Spatial Object Location test after a long delay (240 minutes), but not after shorter delays (15 or 60 minutes) compared to CTL rats. On the Delayed Alternation task, which assessed working memory across delays ranging from 5 to 90 seconds, no group differences were observed. These results are partially in line with previous research that revealed adult impairment on spatial learning and memory tasks after exposure to chronic social instability stress in adolescence. The observed deficits, however, appear to be limited to long-term memory as no group differences were observed during brief periods of retention.

Genetic and Electrophysiological Correlates of Self-Regulation in Adolescence

Self-regulation is considered a powerful predictor of behavioral and mental health outcomes during adolescence and emerging adulthood. In this dissertation I address some electrophysiological and genetic correlates of this important skill set in a series of four studies. Across all studies event-related potentials (ERPs) were recorded as participants responded to tones presented in attended and unattended channels in an auditory selective attention task. In Study 1, examining these ERPs in relation to parental reports on the Behavior Rating Inventory of Executive Function (BRIEF) revealed that an early frontal positivity (EFP) elicited by to-be-ignored/unattended tones was larger in those with poorer self-regulation. As is traditionally found, N1 amplitudes were more negative for the to-be-attended rather than unattended tones. Additionally, N1 latencies to unattended tones correlated with parent-ratings on the BRIEF, where shorter latencies predicted better self-regulation. In Study 2 I tested a model of the associations between selfregulation scores and allelic variations in monoamine neurotransmitter genes, and their concurrent links to ERP markers of attentional control. Allelic variations in dopaminerelated genes predicted both my ERP markers and self-regulatory variables, and played a moderating role in the association between the two. In Study 3 I examined whether training in Integra Mindfulness Martial Arts, an intervention program which trains elements of self-regulation, would lead to improvement in ERP markers of attentional control and parent-report BRIEF scores in a group of adolescents with self-regulatory difficulties. I found that those in the treatment group amplified their processing of attended relative to unattended stimuli over time, and reduced their levels of problematic behaviour whereas those in the waitlist control group showed little to no change on both of these metrics. In Study 4 I examined potential associations between self-regulation and attentional control in a group of emerging adults. Both event-related spectral perturbations (ERSPs) and intertrial coherence (ITC) in the alpha and theta range predicted individual differences in self-regulation. Across the four studies I was able to conclude that real-world self-regulation is indeed associated with the neural markers of attentional control. Targeted interventions focusing on attentional control may improve self-regulation in those experiencing difficulties in this regard.

The nature of bullying among secondary school students /

The purpose of this research was to determine the prevalence and effect of bullying in a secondary school. Six hundred and fifty-nine student volunteers completed a survey which included a quantitative component of 40 questions and 3 questions which required a written response. The results suggest that approximately 1 student in 10 was involved in a bullying situation either as a bully or a victim. As age increased, physical bullying decreased whereas psychological remained high in the senior years of high school. Boys were involved more in bullying than girls, especially in the junior years. The effects of bullying could be devastating to the point of school avoidance or early school leaving. The results also indicate that much of the bullying was not being reported. The implication for the education system is that more needs to be done to prevent bullying, to encourage the reporting of bullying, and to deal with the aftermath of a bullying situation.

Relation of temperament and authoritative parenting on subtypes of adolescent behaviour

Over the years, researchers have investigated direct, conditional, and meditational pathways of adolescent aggression in relation to both temperament and parenting behaviours. However, no study to date has considered these relations with respect to a measure of aggression differentiated by form (e.g., overt, relational) and function (e.g., proactive, reactive). The present study examined the differential association of adolescent temperament and authoritative parenting on four subtypes of aggression. Participants included mothers, fathers, and one adolescent (between the ages of 10-19) from 663 families, recruited through random digit dialing. Parents reported on their child's temperament and occurrence of aggressive behaviours in addition to the perception of their own authoritative parenting. Adolescents reported on their own temperament and aggressive behaviours as well as on both their mother and father's authoritative parenting. Multiple regression analyses confirmed predictions that some aspects of temperament and authoritative parenting provide motivation towards the engagement of different aggressive behaviours. For example, higher negative affect was related to reactive types of aggression, whereas a strong desire for novel or risky behaviours related to proactive aggression. However, differences in effortful control altered the trajectory for both relationships. Higher levels of self-regulation reduced the impact of negative affect on reactive-overt aggression. Greater self-regulation also reduced the impact of surgency on proactive-overt aggression when age was a factor. Structural equation modeling was then used to assess the process through which adolescents become more or less susceptible to impulsive behaviours. Although the issue ofbi-directionality cannot be ruled out, temperament characteristics were the proximal correlate for aggression subtypes as opposed to authoritative parenting dimensions. Effortful control was found to partially mediate the relation between parental acceptancelinvolvement and reactive-relational and reactive-overt aggression, suggesting that higher levels of warmth and support as perceived by the child related to increased levels of self-regulation and emotional control, which in tum lead to less reactive-relational and less reactive-overt types of aggression in adolescents. On the other hand, negative affect partially mediated the relation between parental psychological autonomy granting and these two subtypes of aggression, supporting predictions that higher levels of autonomy granting (perceived independence) related to lower levels of frustration, which in tum lead to less reactive-relational and reactive-overt aggression in adolescents. Both findings provide less evidence for the evocative person-environment correlation and more support for temperament being an open system shaped by experience and authoritative parenting dimensions. As one of the first known studies examining the differential association of authoritative parenting and temperament on aggression subtypes, this study demonstrates the role parents can play in shaping and altering their children's temperament and the effects it can have on aggressive behaviour.

Electrophysiological correlates of performance monitoring in middle and late adolescence

The ability to monitor and evaluate the consequences of ongoing behaviors and coordinate behavioral adjustments seems to rely on networks including the anterior cingulate cortex (ACC) and phasic changes in dopamine activity. Activity (and presumably functional maturation) of the ACC may be indirectly measured using the error-related negativity (ERN), an event-related potential (ERP) component that is hypothesized to reflect activity of the automatic response monitoring system. To date, no studies have examined the measurement reliability of the ERN as a trait-like measure of response monitoring, its development in mid- and late- adolescence as well as its relation to risk-taking and empathic ability, two traits linked to dopaminergic and ACC activity. Utilizing a large sample of 15- and 18-year-old males, the present study examined the test-retest reliability of the ERN, age-related changes in the ERN and other components of the ERP associated with error monitoring (the Pe and CRN), and the relations of the error-related ERP components to personality traits of risk propensity and empathy. Results indicated good test-retest reliability of the ERN providing important validation of the ERN as a stable and possibly trait-like electrophysiological correlate of performance monitoring. Ofthe three components, only the ERN was of greater amplitude for the older adolescents suggesting that its ACC network is functionally late to mature, due to either structural or neurochemical changes with age. Finally, the ERN was smaller for those with high risk propensity and low empathy, while other components associated with error monitoring were not, which suggests that poor ACe function may be associated with the desire to engage in risky behaviors and the ERN may be influenced by the extent of individuals' concern with the outcome of events.

Immediate and enduring effects of corticosterone administration during adolescence and adulthood on anxiety and depressive behavior in male rats

Previous research has shown that the stress hormone corticosterone can increase depressive and anxiety-like behavior in rats as well as dampen the HPA response to a novel stressor (Kalynchuk et aI., 2004; Johnson et aI., 2006). Several studies have also shown that adolescence is a period of increased sensitivity to the negative effects of stressors (reviewed in McCormick et aI., 2010), which are often the result of exposure to corticosterone, and yet there is no research to date examining the effects of corticosterone administration during adolescence. The purpose of these experiments is to determine both the immediate and enduring effects of prolonged exposure to corticosterone in adolescence and adulthood on anxiety-like behavior, depressive behavior, and the HPA response. In Experiment 1 adolescent and adult rats were administered an injection of 40 mg/kg of corticosterone or vehicle daily for 16 days. Ha l f of the rats were then tested on the elevated plus maze (EPM) one day after their last injection, and the following day were tested on the forced swim test (FST). After the FST, which is a stressor, blood samples were collected at three time points, and the plasma concentrations of corticosterone were determined using a radioimmunoassay. The remaining rats were left undisturbed for three weeks, and then underwent the same testing as the first group. Corticosterone treatment had little effect on anxiety-like and depressive behavior, but it did alter the HPA response to the FST. In those rats tested soon after the period of injections, corticosterone dampened the HPA response as compared to vehicle treated rats in both adolescent and adult treated rats. For the adolescent treated rats that were tested several weeks later, corticosterone treatment increased HPA response as compared to the vehicle treated rats, but the same was not true for the adult treated rats. I t was hypothesized that the lack of behavioral effects of the corticosterone treatment may be the result of the vehicle injections inducing a stress response and thereby both groups would have similarly altered behavior. In Experiment 2 rats were administered corticosterone dissolved in their drinking water with 2.5% ethanol, or jus t the 2.5% ethanol or plain water, to determine the effects of corticosterone treatment without a stressor present. The regular drinking water was replaced with treated water for 16 days either during adulthood or adolescence, and as before, rats were either tested in the FST one day after the water was removed or three weeks later. Again there was no effect of treatment on depressive behavior. Similar to what was observed in Experiment 1, corticosterone treatment dampened the HPA response to a stressor for the rats tested soon after the treatment period. However, in Experiment 2 there was no effect of treatment on HPA response in those rats tested several weeks after they were treated. These results indicate that corticosterone can have a lasting effect on the HPA when administered in adolescence by injections but not in drinking water, which is likely because of the different schedules of exposure and rates of absorption between the two administration methods.

The role of self-presentation in adolescent health risk behaviours

Self-presentation has been identified as playing a key role in the perfonnance of various potentially hazardous health behaviours such as substance abuse, eating disorders and reckless behaviours (Leary, Tchividjian, & Kraxberger, 1994; Martin & Leary, 2001; Martin, Leary, & O'Brien, 2001). The present study investigated the role of selfpresentation on adolescent health-risk behaviours. Specifically, this study examined the prevalence of adolescent identified health-risk behaviours rooted in self-presentational motives in youths aged 13-18 years. The current study also identified the specific images associated with these behaviours desired by youth, and the targets of these behaviours. Also, the relationship between these behaviours, and several trait measures (social physique anxiety, public-self consciousness, fear of negative evaluations, selfpresentational efficacy) of self-presentation were examined. Finally, the gender differences in health risk behaviours and self-presentational concerns were examined. Participants in the present study were 96 adolescent students, 34 male and 62 female, recruited from various private schools across Southern Ontario. Students ranged in age from 13 to 18 years for both males (M age = 15.81 years, SD = 1.49) and females (M age = 14.89 years, SD = 1.17) and ranged from grades 8 through 13. Results of the current study suggested that Canadian adolescents between the ages of 13 and 18 years participated in health risk behaviours for self-presentational purposes. Drinking alcohol, skipping school, and performing stunts and dares were identified as the most common health risk behaviours performed for self-presentational purposes by both males and females. Appearing fun and cool were the most commonly reported desired images while appearing brave and mature were the least reported. The most desired target group cited was same sex friends, followed by other sex friends. Trait measures of self-presentational concerns identified females as being higher in public self-consciousness, and social physique anxiety than males. Males were found to be higher in self-presentational efficacy than females. The total number of health risk behaviours was predicted by selfpresentational efficacy and social physique anxiety for males, and social physique anxiety for females. Findings of the current study suggest that Canadian adolescents' health risk behaviours are rooted, in part, in self-presentational motives. Thus far, an educational approach to health interventions has been favoured and/or adopted by teachers, health promoters, and educators (Jessor, 1992). Implications of the current study suggest that although educational interventions are beneficial in presenting the associated risks with certain activities and/or behaviours, one reason this type of approach may be ineffective in changing adolescent behaviour over the long run is that it does not address the strong and prominent influences of interpersonal motives on health damaging behaviour. It is evident that social acceptance and public image are of importance to adolescents, and the desire to make the "right" impression and to achieve peer approval and acceptance often override health and safety concerns (Jessor, 1992). Thus, a self-presentational approach focusing on changing the images associated with the behaviours may be more successful at deterring adolescent health risk behaviours.

An exploration of the experience of implementing the second step violence prevention curriculum in one primary general learning disabilities class /

Violence has always been a part of the human experience, and therefore, a popular topic for research. It is a controversial issue, mostly because the possible sources of violent behaviour are so varied, encompassing both biological and environmental factors. However, very little disagreement is found regarding the severity of this societal problem. Most researchers agree that the number and intensity of aggressive acts among adults and children is growing. Not surprisingly, many educational policies, programs, and curricula have been developed to address this concern. The research favours programs which address the root causes of violence and seek to prevent rather than provide consequences for the undesirable behaviour. But what makes a violence prevention program effective? How should educators choose among the many curricula on the market? After reviewing the literature surrounding violence prevention programs and their effectiveness, The Second Step Violence Prevention Curriculum surfaced as unique in many ways. It was designed to address the root causes of violence in an active, student-centred way. Empathy training, anger management, interpersonal cognitive problem solving, and behavioural social skills form the basis of this program. Published in 1992, the program has been the topic of limited research, almost entirely carried out using quantitative methodologies.The purpose of this study was to understand what happens when the Second Step Violence Prevention Curriculum is implemented with a group of students and teachers. I was not seeking a statistical correlation between the frequency of violence and program delivery, as in most prior research. Rather, I wished to gain a deeper understanding of the impact ofthe program through the eyes of the participants. The Second Step Program was taught to a small, primary level, general learning disabilities class by a teacher and student teacher. Data were gathered using interviews with the teachers, personal observations, staff reports, and my own journal. Common themes across the four types of data collection emerged during the study, and these themes were isolated and explored for meaning. Findings indicate that the program does not offer a "quick fix" to this serious problem. However, several important discoveries were made. The teachers feU that the program was effective despite a lack of concrete evidence to support this claim. They used the Second Step strategies outside their actual instructional time and felt it made them better educators and disciplinarians. The students did not display a marked change in their behaviour during or after the program implementation, but they were better able to speak about their actions, the source of their aggression, and the alternatives which were available. Although they were not yet transferring their knowledge into positive action,a heightened awareness was evident. Finally, staff reports and my own journal led me to a deeper understanding ofhow perception frames reality. The perception that the program was working led everyone to feel more empowered when a violent incident occurred, and efforts were made to address the cause rather than merely to offer consequences. A general feeling that we were addressing the problem in a productive way was prevalent among the staff and students involved. The findings from this investigation have many implications for research and practice. Further study into the realm of violence prevention is greatly needed, using a balance of quantitative and qualitative methodologies. Such a serious problem can only be effectively addressed with a greater understanding of its complexities. This study also demonstrates the overall positive impact of the Second Step Violence Prevention Curriculum and, therefore, supports its continued use in our schools.

What nourishes the spirit of adolescents in the classroom? : a qualitative study into the gateways of adolescents' souls /

This thesis investigated the question, "What nourishes the adolescent spirit in the classroom?" Action research was conducted by the teacher of 16 grade 8 participants. By undergoing Kessler's (2000) "Passages Program," the students participated in 6 sessions which exposed them to a holistic intrapersonal curriculum. Student journal responses were documented after each session. The action researcher also kept journal reflections after each session. Upon completion of the 6 sessions, a postinterview was conducted which posed the research question. The research found that the adolescent spirit gets nourished through encouragement by the teacher, peers, and parents. This increases their competency, which increases their confidence, and ultimately their self-esteem goes up, which affects their selfconcept. In addition, the role of the teacher permeates every aspect of what nourishes the adolescent spirit in the classroom. In addition to the encouragement of the student, how a teacher teaches plays a vital role. A holistic approach to teaching provided the best atmosphere for the adolescent. It promoted creativity and choice, which stimulated the spirit of the adolescent. By working from a holistic philosophy, the teacher/action researcher created an environment conducive to teaching the whole person, which ultimately nourished the participants' spirit. The research highlighted that in order for this type of environment to exist the teacher needs to make a conscious and deliberate effort to look within and develop their inner self before they can begin to promote this type of classroom for the adolescents they teach. When teachers and students develop an inner life together, they can begin to work in harmony to achieve an atmosphere where the teaching and learning environment becomes one seamless transaction. Only then can one's whole potential be realized.

Emergence of normative beliefs legitimizing antisocial behaviour in adolescents : the roles of monitoring, attachment, and temperament /

Beliefs about the rightness or wrongness of engaging in various antisocial acts, referred to here as nonnative beliefs legitimizing antisocial behaviour (nblab), have been shown to playa role in the emergence oflater antisocial behaviour. The current study represented an attempt to understand whether parental monitoring and parent-child attachment have differential relationships with these antisocial nonnative beliefs in adolescents of different temperaments. The participants, 7135 adolescents in 25 high schools (ages 10- 18 years, M = 15.7) completed a wide-ranging questionnaire as part of the broad Youth Lifestyle Choices - Community University Research Alliance project, whose goal is to identify and describe the major developmental pathways of risk behaviours and resilience in youth. Two aspects of monitoring (monitoring knowledge and surveillance/tracking), attachment security, and two measures of temperament (activity level and approach) were examined for main effects and in interactions as predictors of adolescent nonnative beliefs. All of these measures were based on adolescent self-ratings on either 3- or 4-point Likert-type scales. Several important results emerged from the study. Males were higher than females in nblab; parental monitoring knowledge and adolescent attachment security were negatively related to nblab; and temperamental activity level was positively related. Monitoring knowledge, the strongest of the predictors, was much more strongly related to nonnative beliefs than was parental surveillance/tracking, supporting the contention that it is how much parents actually know, and not their surveillance efforts, that predict adolescent nonnative beliefs. A surprising finding that is of the utmost importance was that, although several of the interactions tested were significant, none were considered to be of a meaningful magnitude (defined as sr^ > .01). The current study supported the suggestion that normative beliefs legitimizing antisocial behaviour are multiply determined, and the results were discussed with respect to the observed differential relations of parental monitoring, parent-child attachment, temperament, age, and gender to antisocial normative beliefs in adolescents. Also discussed were the need to test other parenting, temperament, and other variables that may be involved in the development of nblab; the need to directly test possible mechanisms explaining the links among the variables; and the usefulness of longitudinal research in determining possible directions of causality and developmental changes in the relationships.

Determinants of left ventricular mass as measured by Doppler echocardiography in pre-adolescents

This study examined factors contributing to the differences in left ventricular mass as measured by Doppler echocardiography in children. Fourteen boys (10.3 ± 0.3 years of age) and 1 1 girls (10.5 ± 0.4 years of age) participated in the study. Height and weight were measured, and relative body fat was determined from the measurement of skinfold thickness according to Slaughter et al. (1988). Lean Body Mass was then calculated by subtracting the fat mass from the total body mass. Sexual maturation was self-assessed using the stages of sexual maturation by Tanner (1962). Both pubic hair development and genital (penis or breast for boys and girls respectively) development were used to determine sexual maturation. Carotid Pulse pressure was assessed by applanation tomometry in the left carotid artery. Cardiac mass was measured by Doppler Echocardiography. Images of cardiac structures were taken using B-Mode and were then translated to M- Mode. The dimensions at the end diastole were obtained at the onset of the QRS complex of the electrocardiogram in a plane through a standard position. Measurements included: (a) the diameter of the left ventricle at the end diastole was measured from the septum edge to the endocardium mean border, (b) the posterior wall was measured as the distance from to anterior wall to the epicardium surface, and (c) the interventricular septum was quantified as the distance from the surface of the left ventricle border to the right ventricle septum surface. Systolic time measurements were taken at the peak of the T-wave of the electrocardiogram. Each measurement was taken three to five times before averaging. Average values were used to calculate cardiac mass using the following equation (Deveraux et al. 1986). Weekly physical activity metabolic equivalent was calculated using a standardize activity questionnaire (Godin and Shepard, 1985) and peakV02 was measured on a cycloergometer. There were no significant differences in cardiovascular mesurements between boys and girls. Left ventricular mass was correlated (p<0.05) with size, maturation, peakV02 and physical activity metabolic equivalent. In boys, lean body mass alone explained 36% of the variance in left ventricular mass while weight was the single strongest predictor of left ventricular mass (R =0.80) in girls. Lean body mass, genital developemnt and physical activity metabolic equivalent together explained 46% and 81% in boys and girls, respectively. However, the combination of lean body mass, genital development and peakV02 (ml kgLBM^ min"') explained up to 84% of the variance in left ventricular mass in girls, but added nothing in boys. It is concluded that left ventricular mass was not statistically different between pre-adolescent boys and girls suggesting that hormonal, and therefore, body size changes in adolescence have a main effect on cardiac development and its final outcome. Although body size parameters were the strongest correlates of left ventricular mass in this pre-adolescent group of children, to our knowledge, this is the first study to report that sexual maturation, as well as physical activity and fitness, are also strong associated with left ventricular mass in pre-adolescents, especially young females. Arterial variables, such as systolic blood pressure and carotid pulse pressure, are not strong determinants of left ventricular mass in this pre-adolescent group. In general, these data suggest that although there is no gender differences in the absolute values of left ventricular mass, as children grow, the factors that determine cardiac mass differ between the genders, even in the same pre-adolescent age.