Racial inequality in educational and occupational attainment has been shown to be related to racial inequality in test scores and cognitive skills. Most research and policy attention has been given to the ability of schools to equalize test scores. I argue that a major reason why researchers have been unable to explain why schools have not closed the gap is because by the time children begin school it may be too late. Cognitive skills develop from infancy and as such, it should be unsurprising that by the time children are five years old the differences across groups are firmly established. Thus, this research attempts to uncover where the racial test-score gap begins by examining infants. I perform a series of analyses using ordinary least squares regression (OLS) and structural equation modeling (SEM) using the first wave of the Early Childhood Longitudinal Survey--Birth cohort (ECLS-B). I utilize the mother's race, rather than the child's race, in the analyses because looking at the mother's race makes the most logical sense since the mother's race is more likely than the child's to determine household income, marital status, mother's education, parenting styles, and so on. I demonstrate that there is little to no raw gap in cognitive skills between the infants of White and Black mothers in the United States. However, through SEM I find that when one controls for social, human, and financial capital, and for differences in health and type of childcare, the infants of African American mothers would actually do better than the infants of White mothers because of their precocious motor development. I find no support for genetics and childcare and only limited support for financial and human capital as mediators of the gap. However, there is support for family social capital and low birth weight as key mediators of the small Black-White test score gap in infancy.

Pesquisas recentes vêm encontrando que alunos negros têm pior desempenho escolar que alunos brancos em testes cognitivos padronizados. A segregação racial é freqüentemente apontada na literatura internacional como uma das principais responsáveis por essa diferença. Nessa dissertação, foi analisado o efeito da segregação racial escolar no diferencial de proficiência escolar entre alunos brancos e negros do ensino fundamental brasileiro. Nos modelos estimados, mesmo após a utilização de diversos controles, foi encontrada evidência de que onde há maior segregação, os negros tem pior desempenho relativamente aos brancos. / Recent research have found that black students have worse schoolar performance than white students in standardized cognitive tests. Racial segregation is frequently pointed out as one of the main factors behind this scenario in international literature. We have studied the effects of racial seggregation on the black-white grade gap in Brazil. In the estimated models, even after the inclusion of several control variables, we have found that where the racial seggregation is higher, the grade differential is higher against black students.

Pesquisas recentes vêm encontrando que alunos negros têm pior desempenho escolar que alunos brancos em testes cognitivos padronizados. A segregação racial é freqüentemente apontada na literatura internacional como uma das principais responsáveis por essa diferença. Nessa dissertação, foi analisado o efeito da segregação racial escolar no diferencial de proficiência escolar entre alunos brancos e negros do ensino fundamental brasileiro. Nos modelos estimados, mesmo após a utilização de diversos controles, foi encontrada evidência de que onde há maior segregação, os negros tem pior desempenho relativamente aos brancos. / Recent research have found that black students have worse schoolar performance than white students in standardized cognitive tests. Racial segregation is frequently pointed out as one of the main factors behind this scenario in international literature. We have studied the effects of racial seggregation on the black-white grade gap in Brazil. In the estimated models, even after the inclusion of several control variables, we have found that where the racial seggregation is higher, the grade differential is higher against black students.

This dissertation consists of three essays studying the effects of collective household decisions on early childhood development from both empirical and theoretical perspectives. The first chapter outlines the dissertation, by presenting the motivations, methods, conclusions, and policy implications for the entire dissertation. Chapter two examines early childhood development using a collective model with children's cognitive production. We jointly estimate the home input demand with children's cognitive production functions based on a simultaneous equations model. Biases are considered that are caused by the non-random selection of time inputs and possible correlations across inputs and outcomes functions. A direct measure of time inputs relying on children's time diaries from the Child Development Supplement of the Panel Study of Income Dynamics (PSID-CDS) has been constructed. We thereby relax the assumption that there is no difference between parental time spent on children and leisure. Our results show that parental time inputs, especially the active time interacting with children's daily activities, have substantial effects on both children's math and reading test scores. The time inputs vary across parents' age, race, and eduction levels. In chapter three, we conduct a standard Blinder-Oaxaca decomposition to evaluate the role of home inputs in the black-white test score gaps based on the empirical model presented in chapter two. Aside from the finding that children's ability accounts for a large proportion of the differences, we find that home inputs can also explain a significant portion of the gap. When the maternal time is equalized at the average levels of white children, the racial differences in children's reading and math test scores can be closed by approximately 30%-50%. The last chapter extends a collective model with household production to the general equilibrium framework. We concentrate on the impacts of a global bargaining power shift within the household on children's cognitive achievement, especially on those who live with single mothers. The model shows that a global bargaining power change in favor of the female may not necessarily be beneficial to the children living with their single mothers. An increase of female's market equilibrium wage rate as a result of reduced labor supply by married women may induce single mothers to work longer hours, spend less time with children, and compensate them with more monetary investment compared with the case when the equilibrium wage rate stays constant. / Ph. D.

Made available in DSpace on 2016-06-02T19:22:49Z (GMT). No. of bitstreams: 1 1958.pdf: 10581288 bytes, checksum: 1dc2b5264737849b6a8842144f1ad052 (MD5) Previous issue date: 2008-05-21 / Financiadora de Estudos e Projetos / The post-traumatic stress disorder (PTSD) affects a portion of subjects exposed to a traumatic event. This disorder leads to long-term alterations in the hypothalamus-pituitaryadrenal (HPA) axis, autonomic and cognitive function. The aim of our study was to evaluate whether the animal model of PTSD proposed for rats could be used in mice and, to evaluate the effect of benzodiazepine, tricycle antidepressant and selective serotonin reuptake inhibitor drugs in the PTSD model. For this we realized the following experiments: Experiment 1- The test consisted of exposure the male mice to inescapable electric footshock (0.3 mA) in the black side (BS) of the black-white box (BW). In the 7th, 14th and 21th day, mice were reexposed to the traumatic reminder on the white side (WS) or BS for 2 min, without footshock. In the 29th day, the animals were submitted to elevated plus-maze (EPM) for record the anxiety indexes [percentage of open arm entries (%OA) and percentage of open arm time (%OT) and as well as general locomotor activity, closed arm entries (CE)]. On day 34 the same animals were submitted to BW test for record the latency to escape (LE) from WS and time spent on WS of the BW box. Experiment 2 the same procedure of experiment 1 was performed, except that the animals were re-exposed at 7th, 14th e 21th days to reminder situation only in WS of BW box for 2 min, without footshock. On day 29th, the animals were exposed to EPM, 30 min after receiving treatment with midazolam. In 34th day the same animals after receiving treatment with midazolam were submitted to BW box test. Experiment 3, 4 and 5 - the same procedure was adopted from experiment 2, except that in 29th day, the animals were not submitted to EPM test and on 34th day 30 minutes after treatment with midazolam, imipramine and sertraline were submitted to BW box. Two-way ANOVA (stimulus x place remainder or treatment) followed by Duncan test showed that PTSD model increased anxiety in mice (P<0.05). The re-exposure in BS promoted anxiogenic-like effect extinction of the model. The midazolam treatment (1.0 and 2.0 mg/kg, i.p.) produced anxiolytic-like effect in maze-mice (P < 0.05) and the 0.5 mg/kg decreased latency to escape of WS (P < 0.05) of BW box and increased the exploratory activity, suggesting involvement of this GABA-benzodiazepine agonist on this PTSD modulation. The EPM test does not interfere in the evaluation of the BW test. It is important to note that no other behaviors were significantly altered by imipramine per se (P < 0.05). The sertraline (5.0 mg/kg), selective serotonin reuptake inhibitor, produced anxiolytic-like effect in the BW test (P < 0.05) and increase exploration activity. These results suggest that the employed PTSD model to study neurobiological disturbances associated with this disorder. / O Transtorno de Estresse Pós-Traumático (TEPT) afeta uma parcela de indivíduos que são expostos a um evento traumático. Este distúrbio induz em longo prazo alterações no eixo HPA, autonômicas e cognitivas. O objetivo deste estudo foi avaliar se o modelo animal de TEPT proposto para ratos poderia ser utilizado em camundongos e investigar o efeito dos fármacos benzodiazepínico, antidepressivo tricíclico e inibidor seletivo da recaptação de serotonina, no modelo de TEPT. Para isso realizamos os seguintes experimentos: Experimento 1- O teste consistiu em submeter camundongos machos, Suíço-albino ao choque inescapável (0,3mA) nas patas no lado escuro (LE) da caixa claro-escuro (CE). No 7º, 14º e 21º dia os camundongos foram reexpostos a situação de lembrança no lado claro (LC) ou LE da caixa por 2 min, sem choque. No 29º dia os animais foram expostos ao labirinto em cruz elevado (LCE), para o registro dos índices de ansiedade [porcentagem de entradas (%EBA) e de tempo gasto nos braços abertos (%TBA) e atividade locomotora, entrada nos braços fechados (EBF)]. No 34º dia os mesmos animais foram submetidos ao teste CE para o registro da latência de fuga (LF) e do tempo gasto no LC da caixa CE. Experimento 2 o mesmo procedimento do experimento 1 foi adotado, exceto que os animais foram reexpostos no 7º, 14º e 21º dia a situação de lembrança apenas no LC da caixa por 2 min, sem choque. No 29º dia os animais, 30 min após receberem tratamento com midazolam, foram expostos ao labirinto em cruz elevado (LCE). No 34º dia os mesmos animais após receberem o mesmo tratamento farmacológico, foram submetidos ao teste CE. Experimento 3, 4 e 5 o mesmo procedimento do experimento 2 foi adotado, exceto que no 29º dia os animais não foram submetidos ao LCE e no 34º dia, 30 min após receberem tratamento com midazolam, imipramina e sertralina foram submetidos ao teste CE. A ANOVA de duas vias (estímulo x local da SL ou tratamento) seguido do teste de Duncan mostrou que o modelo de TEPT produziu aumento da ansiedade nos camundongos (P < 0,05). As reexposições no LE promoveram extinção do efeito ansiogênico do modelo. O tratamento com midazolam (1,0 e 2,0 mg/kg) produziu efeito ansiolítico no LCE (P < 0,05), e a dose de 0,5 mg/kg reduziu a latência de fuga do ambiente claro (P < 0,05) no teste CE e aumentou a atividade exploratória, sugerindo o envolvimento deste agonista GABA-benzodiazepínico na modulação do TEPT. O LCE não interferiu na avaliação do teste CE. A imipramina não apresentou efeito sobre os camundongos (P > 0,05), ou seja, ausência de efeito deste antidepressivo tricíclico nos sintomas do TEPT. A sertralina (5,0 mg/kg) produziu efeito ansiolítico no teste CE (P < 0,05) e aumento na atividade exploratória, mostrando o envolvimento deste inibidor seletivo da recaptação de serotonina na modulação do modelo. Estes resultados sugerem que o modelo de TEPT utilizado poderá ser empregado para o estudo das alterações neurobiológicas envolvidas neste distúrbio.