With increasing life expectancy and global population of older adults, preserving cog- nitive function throughout life represents a growing priority. Numerous approaches to cognitive enhancement exist, but few have scientific merit. Among the most preva- lent – and commercialized – approaches are cognitive training (“brain training”) and non-invasive brain stimulation through electric currents applied at the surface of the scalp. The present dissertation describes a collection of work contextualizing the appeal of these cognitive enhancement methods and addressing some of the most pervasive limitations of research in this field thus far. One largely ignored issue in cognitive intervention research pertains to people’s expectations of programs and their relationship with intervention outcomes. In a series of initial studies, we developed and validated the Expectation Assessment Scale (EAS), a tool created to measure as well as prime expectations of outcomes in the context of cognitive enhancement interventions. In our first two studies, we probed expectations of cognitive training or non-invasive brain stimulation in over 1,000 young, middle-aged, and older adults. Ratings on the EAS suggested that older adults may have particularly high expectations of cognitive training, but that expectations can be primed to increase or decrease – at least in hypothetical scenarios. We used these data to assess the psychometric properties of the EAS with item-response theory, and confirmed its internal consistency. Next, we incorporated the EAS into two cognitive enhancement trials, one in- vestigating a computerized cognitive training intervention in nearly 100 older adults and another examining non-invasive brain stimulation in nearly 100 young adults. Both trials had a double-blind balanced-placebo design in which participants were assigned to the intervention or control condition, and then subdivided to receive ei- ther high or low expectation priming (i.e., primed to have high or low expectations of the program’s effectiveness). Although expectation ratings replicated our previous findings, results from these trials suggest little, if any, effect of either expectations or the intervention on performance outcomes. We nevertheless found that participants enjoyed their assigned program and that those who received high expectation prim- ing tended to report a more positive experience. Our findings put into question the effectiveness of such interventions and support the need for more rigorous trials of cognitive enhancement.

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Hipótese: A principal hipótese deste estudo foi que o uso de enxaguatório placebo associado ao tratamento periodontal não cirúrgico é tão eficaz quanto o uso de clorexidina para bochecho. Objetivo: O objetivo deste ensaio clínico controlado randomizado foi avaliar a resposta placebo em dois modelos terapêuticos periodontais; terapia periodontal mecânica convencional por quadrante e `one-stage full-mouth disinfection. Metodologia: Para responder esta hipótese foram incluídos indivíduos com periodontite crônica distribuídos aleatoriamente em seis grupos, Full mouth (Full Mouth disinfection (FMD), Full Mouth placebo (FMP) e Full Mouth Controle (FMC) e quadrante (Raspagem convencional Clorexidina (RCC), raspagem convencional placebo (RCP) e raspagem convencional (RC), sendo cada grupo com 10 indivíduos. Mensurações tanto no momento inicial (baseline), 90 e 180 dias após os procedimentos de raspagem foram considerados na avaliação geral da resposta placebo em toda a população. Nesta análise foram consideradas medidas clínicas de profundidade de sondagem, nível de inserção clínico, índice de placa e gengival. Em adição, o impacto do efeito placebo foi também investigado com relação à avaliação das analises salivares de proteína total, atividade argininolítica e nitrito. A avaliação de dor/ansiedade em função da intervenção, qualidade de vida e impacto sobre a saúde bucal foram também objeto de análise durante todo o ensaio. O experimento foi conduzido no delineamento casualizado com 10 repetições. Os dados foram submetidos à análise de variância, os modelos de regressão foram testados pelo teste de Fischer, os coeficientes angulares dos modelos de regressão foram testados pelo teste t, as médias foram comparadas pelo teste Duncan a 5% de probabilidade e a análise de correlação teve a significância testada pelo teste t. Resultados: Os grupos FMP e RCP tiveram uma tendência à aumentar a atividade da arginase aos 90 dias e diminuir aos 180 dias, porém na concentração de nitrito foi observada uma diminuição em todos os tempos. Nos parâmetros clínicos observou-se uma diminuição de suas médias em todos os grupos avaliados. Com relação aos questionários observou-se uma tendência às respostas em escores que indicavam pouca dor pós-tratamento e a maioria respondeu concordar que a saúde bucal está relacionada com a qualidade de vida. Conclusão: Todos os grupos apresentaram melhora nas médias, relacionadas aos parâmetros clínicos, após o tratamento periodontal, porém não foi estatisticamente significante. Os grupos placebo não apresentaram melhoras significantes que se possa afirmar sobre a influência da resposta placebo, observando-se uma resposta negativa à nossa hipótese. / Hypothesis: The main hypothesis of this study was that the use of mouthwash placebo combined with non-surgical periodontal treatment is as effective as the use of chlorhexidine mouthwash. Objective: The objective of this randomized controlled clinical trial was to evaluate the placebo response in two periodontal therapeutic models; conventional mechanical periodontal therapy quadrant and `one-stage full-mouth disinfection. Methodology: To answer this hypothesis, subjects with chronic periodontitis were randomly divided into 6 groups, Full mouth (FMD, and FMC FMP) and quadrant (RCC, RC and RCP), each group had 10 subjects in. Measurements were taken at baseline (baseline), 90 and 180 days after scraping procedures were considered in the overall evaluation of the placebo response in the whole population. This analysis considered clinical measures of probing depth, clinical attachment level, plaque index, gingival. In addition, the impact of placebo effect was also investigated in the analysis of the salivary total protein and activity argininolítica nitrite assessment. The assessment of pain / anxiety due to the intervention, quality of life and impact on oral health were also analyzed throughout the test. The experiment was conducted in randomized design with 10 replications. The data was subjected to analysis of variance, regression models were tested by Fischers test, the slopes of the regression models were tested by t test, means were compared by Duncan test at 5% probability and correlation analysis had its significance tested by t test. Results: The FMP and RCP groups had a tendency to increase the activity of arginase at 90 days and decrease at 180 days, but the nitrite concentration decrease was observed at all times. In clinical parameters a decrease in their average in all groups evaluated was observed. Regarding the questionnaires, they revealed a trend in the responses that indicated little pain scores after treatment and most responses agreed that oral health is related to quality of life. Conclusion: All groups showed improvement in average, related to clinical parameters after periodontal treatment, however it was not statistically significant. The placebo group showed no significant improvements that can be said about the influence of the placebo response, observing a negative answer to our hypothesis.