Latent Dirichlet allocation (LDA) topic models are increasingly being used in communication research. Yet, questions regarding reliability and validity of the approach have received little attention thus far. In applying LDA to textual data, researchers need to tackle at least four major challenges that affect these criteria: (a) appropriate pre-processing of the text collection; (b) adequate selection of model parameters, including the number of topics to be generated; (c) evaluation of the model's reliability; and (d) the process of validly interpreting the resulting topics. We review the research literature dealing with these questions and propose a methodology that approaches these challenges. Our overall goal is to make LDA topic modeling more accessible to communication researchers and to ensure compliance with disciplinary standards. Consequently, we develop a brief hands-on user guide for applying LDA topic modeling. We demonstrate the value of our approach with empirical data from an ongoing research project.
In this paper we seek to understand the impact of the macro-political context on power configurations within policy subsystems. For this purpose we systematically compare policy networks in three major policy subsystems and seven Western European countries (and the EU) on the basis of a typology for the power configurations within policy subsystems. We link the European, domestic and policy-specific context to our typology of policy networks. To test the hypotheses we conduct empirical network and reputational analysis of 345 interviews with key policy makers. The results point not only to the importance of the EU context, but also to the complex interplay of domestic and policy-specific contexts for understanding domestic power configurations. Domestic power configurations vary not only from country to country, but also within the countries depending on the policy domain.
Skepticism toward climate change has a long tradition in the United States. We focus on mass media as the conveyors of the image of climate change and ask: Is climate change skepticism still a characteristic of US print media coverage? If so, to what degree and in what form? And which factors might pave the way for skeptics entering mass media debates? We conducted a quantitative content analysis of US print media during one year (1 June 2012 to 31 May 2013). Our results show that the debate has changed: fundamental forms of climate change skepticism (such as denial of anthropogenic causes) have been abandoned in the coverage, being replaced by more subtle forms (such as the goal to avoid binding regulations). We find no evidence for the norm of journalistic balance, nor do our data support the idea that it is the conservative press that boosts skepticism.
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