Breakfast frequency and quality may affect glycemia and appetite in adults and children.

Observational studies of breakfast frequency in children and adults suggest an inverse (protective) association between the frequency of eating breakfast and the risk for obesity and chronic diseases such as type 2 diabetes. More prospective studies with stronger designs are needed, as are experimental studies on this topic. In addition, above and beyond breakfast frequency, the roles of dietary quality and composition need to be studied in the context of eating or skipping breakfast. Experimental studies are also necessary to rigorously test causality and biological mechanisms. Therefore, we conducted 2 pilot experimental studies to examine some of the effects of breakfast skipping and breakfast composition on blood glucose and appetite in children and adults. Our results suggest that breakfast frequency and quality may be related in causal ways to appetite controls and blood sugar control, supporting the hypothesis that the breakfast meal and its quality may have important causal implications for the risk of obesity and type 2 diabetes.

An empirical examination of sex differences in scoring preschool children's aggression.

Sex differences in adults' observations and ratings of children's aggression was studied in a sample of preschool children (N=89, mean age=44.00months, SD=8.48). When examining the direct observations made by trained observers, male observers, relative to female observers, more frequently recorded aggressive bouts, especially of boys. On rating scales assessing aggression, trained male raters also gave higher aggressive ratings than female raters. Lastly, we compared the ratings of trained female raters and female teachers on the same scale and found no differences. Results are discussed in terms male raters' and observers' prior experiences in activating their experiential schemata where males' greater experience in aggression, relative to that of females, leads them to perceive greater levels of aggression.

Behavioral and social cognitive processes in preschool children's social dominance.

This longitudinal, naturalistic study addressed behavioral and social cognitive processes implicated in preschool children's social dominance. In the first objective, we examined the degree to which peer aggression, affiliation, and postaggression reconciliation predicted social dominance across a school year. Consistent with predictions, all three predicted dominance early in the year while only affiliation predicted dominance later in the year, suggesting that aggression, affiliation, and reconciliation were used to establish social dominance where affiliation was used to maintain it. In the second, exploratory, objective we tested the relative importance of social dominance and reconciliation (the Machiavellian and Vygotskian intelligence hypotheses, respectively) in predicting theory of mind/false belief. Results indicated that social dominance accounted for significant variance, beyond that related to reconciliation and affiliation, in predicting theory of mind/false belief status. Results are discussed in terms of specific behavioral and social cognitive processes employed in establishing and maintaining social dominance.

A short-term longitudinal study of preschoolers' (Homo sapiens) sex segregation: the role of physical activity, sex, and time.

The interactive influence of preschool children's level of physical activity, sex, and time on the degree of sex segregation was assessed. A sample of nursery school children was observed across much of a school year, and levels of physical activity and sex segregation were sampled during their free play periods. Following sexual selection theory, we predicted a Sex X Time X Physical Activity interaction on segregation such that high-activity girls early in the school year would interact with boys but, with time, the high-activity girls would be segregated among themselves. Boys (both high- and low-activity) should remain segregated across the year. The hypothesis was supported, and results are discussed in terms of the interactive role of biology and socialization on sex segregation.

Social dominance in preschool classrooms.

The authors examined preschoolers' aggressive and cooperative behaviors and their associations with social dominance. First and as predicted, directly observed aggressive interactions decreased across the school year, and same-sex aggression occurred more frequently than cross-sex aggression. Next, the authors examined the relation between aggression and reconciliation, cooperation, and social display variables. Teacher ratings of children's aggression related to observed aggression but not to observed "wins" of aggressive bouts. Instead, wins were related to cooperation and display variables. Finally, they examined the relative power of wins and cooperation in predicting 2 measures of social dominance. After age was controlled, wins alone predicted teacher-rated social dominance. Results are discussed in terms of different forms of competition and how school ethos affects these forms.

The development of preschool children's (Homo sapiens) uses of objects and their role in peer group centrality.

The ways in which objects were used by preschool children (Homo sapiens) was examined by directly observing them across one school year. In the first objective we documented the relative occurrence of different forms of object use and their developmental growth curves. Second, we examined the role of different types of object use, as well as novel and varied uses of objects, in predicting peer group centrality. Results indicated that noninstrumental object play was the most frequently observed category, followed by tool use, exploration, and construction; sex moderated the growth curve of children's exploration. Noninstrumental object play, not other types of object use, was significantly related to novel and varied object uses and only the latter category predicted peer group centrality. Results are discussed in terms of the social transmission of novel object use.

A longitudinal study of preschool children's (Homo sapiens) sex segregation.

In this 2-year longitudinal study, we hypothesized that sex of the human child (Homo sapiens), differences in physical activity, and time of the year would interact to influence preschool children's sex segregation. We also hypothesized that activity would differentially relate to peer rejection for boys and girls. Consistent with the first hypothesis, high-activity girls started off as the most integrated group but became more segregated with time, whereas high-activity boys remained the most segregated group across the duration of the study. The second hypothesis was also supported: For girls only, activity was significantly related to peer rejection during Year 1 only, the time when high-activity girls also interacted frequently with boys. Results are discussed in terms of sexual selection theory and gender boundary violations.

Perceptions and functions of play and real fighting in early adolescence.

The hypothesis is tested that adolescent boys' (mean age of 12.8 years) intrasexual rough-and-tumble play (R&T) is used for dominance and intersexual R&T is used to establish heterosexual relationships. In Study 1, boys' observed R&T was related to both dominance and aggression. In the first half of the school year, R&T occurred primarily between males, possibly to establish dominance. In the second half of the year, both boys and girls engaged in R&T, possibly to establish heterosexual relationships. Counter to the hypothesis, observed aggression increased across the year. In Study 2, youngsters viewed taped R&T bouts in which they were participants or nonparticipants. Participant, more than nonparticipant, males saw R&T as related to dominance whereas participant, more than nonparticipant, females saw it as playful.

A sexual selection theory longitudinal analysis of sexual segregation and integration in early adolescence.

The three objectives in this longitudinal study were motivated by sexual selection theory. The theory specifies the role of sexually segregated groups and the effects of dominance in male groups and relational/indirect aggression in female groups for heterosexual relationships. Using a multi-method, multi-informant, longitudinal design we studied youngsters (N=138) across their first two years of middle school. First, we examined the nature of change in segregation and dating popularity across two years during early adolescence. Second, a model derived from sexual selection theory is tested to explain the ways in which boys and girls are nominated for hypothetical dates (dating popularity). Third, we examined the role of "poke and push courtship" behavior in boys' and girls' dating popularity. Results indicate that although groups did not become more integrated with time, changes in peer group sexual integration co-varied dynamically with dating popularity. Secondly, dominance-related strategies were more important for boys than girls in dating popularity whereas indirect, or relational, aggression strategies were more important for girls than boys. Third, "poke and push courtship" behaviors did not influence peer group integration or dating.