Critical exhibitions represent a trend in the science museums landscape. These installations, often issues-based, tend to: display complex socio-scientific issues, approach controversy, challenge visitors' points of view, and engage visitors in active ways. Informed by theory in the fields of science communication, scientific literacy and science museums, I examined visitors', curators' and museum educators' perspectives on critical exhibitions in Brazil and Canada. I also investigated dimensions of engagement that visitors experienced in these exhibits.

Using a qualitative approach and multiple case study as a research strategy, I examined two individual cases: the exhibits Alerts: Knowing to Prevent. Drugs, Tobacco and Alcohol and Preventing Youth Pregnancy , displayed at the Catavento museum (Sao Paulo, Brazil), and Our World: BMO Sustainability Gallery displayed at the Science World (Vancouver, Canada). In both research sites I conducted observations and interviews with visitors, and interviews with the museum teams. I also collected documents and materials related to the exhibits. In the initial analytical stage, I built individual portraits of each exhibit. In the subsequent stage, I performed cross-case analysis, explored similarities and differences across cases, and generated some theoretical insights about the goals and contributions of critical exhibitions to the science museum landscape.

Findings of this work reflect the different sets of motivations behind each exhibit, identifying progressive views of scientific literacy with the creation of the Brazilian exhibits. These views include citizen science approaches, associations between socio-scientific issues and cross-curricular themes, nature of science perspectives and civic scientific literacy. The findings also revealed that barriers associated with the creation of these critical exhibitions are related to operational funding, visitor expectations about leisure time and affinity constraints.

Outcomes of this study also reflect the dimensions of visitors' engagement that emerge when different models of science communication are articulated. These dimensions are particularly complex and deep when the deficit model is used to support other models in the exhibit, including dialogue, participation and dissent, and conflict/action. It is hoped that these findings will impact the work currently done in science museums and the ways in which critical exhibitions can promote public engagement and scientific literacy for citizenship.

$=Exposicoes de ciencia criticas representam uma nova direcao para museus de ciencias. Comumente estas exposicoes baseiam-se em problemas, apresentam assuntos sociocientificos, abordam controversias e chamam os visitantes para participar ativamente. Por meio de referenciais teoricos nas areas de comunicacao publica da ciencia, alfabetizacao cientifica e museus de ciencias, explorei perspectivas de curadores e educadores sobre exposicoes de ciencia criticas em Brasil e Canada. Investiguei, tambem, dimensoes de engajamento do publico.

$=Usando uma abordagem qualitativa, e estudos de caso como estrategia de pesquisa, considerei dois casos: as exposicoes Alertas. Conhecer para prevenir. Drogas, tabaco e alcool e Prevenindo a gravidez juvenil do espaco cultural de ciencia Catavento (Sao Paulo, Brasil), e Our World: BMO Sustainability Gallery (Nosso planeta: BMO Galleria de Sustentabilidade) do Science World (Vancouver, Canada). Nestes espacos fiz observacoes e entrevistas com visitantes e entrevistei curadores e educadores. Coletei, ainda, documentos e materiais relacionados as exposicoes. No primeiro momento da analise, criei 'retratos' de cada exposicao. No segundo momento, fiz uma analise entre casos, explorando similaridade e diferencas e gerando algumas reflexoes teoricas sobre os objetivos e contribuicoes de exposicoes de ciencia criticas para os museus de ciencias.

$=Resultados deste trabalho refletem diferentes arranjos de motivacoes por tras de cada exposicao, tendo visoes mais progressistas de alfabetizacao cientificas associadas a criacao das exposicoes Brasileiras. Estas visoes incluem ciencia cidada, relacoes entre assuntos sociocientificos e temas curriculares transversais, natureza da ciencia e alfabetizacao cientifica civica. Os resultados tambem revelam obstaculos para a criacao e montagem destas exposicoes, tendo entre eles recursos economicos, patrocinadores, expectativas dos visitantes sobre o uso do tempo livre e afinidade com os temas abordados.

$=Dados deste estudo tambem revelam as dimensoes de engajamento do publico que emergem quando diferentes modelos de comunicacao publica da ciencia sao articulados. Estas dimensoes sao particularmente complexas quando o modelo de deficit tende a dar suporte a outros modelos como dialogo, participacao e vivencia de conflito/acao. Espera-se que estes resultados impactem o trabalho desenvolvido por museus de ciencia e as formas em que as exposicoes de ciencia criticas podem contribuir para promover engajamento publico e alfabetizacao cientifica para a cidadania.