We examine the popular Personas method and consider claims that personas can reflect empirical data and serve as an information source for development teams. We argue that there are significant methodological and practical difficulties for personas. It is difficult to determine how many, if any, users are represented by a persona, and thus is difficult to know whether a persona is relevant for intended users. Personas cannot be adequately verified or falsified and therefore have no demonstrable validity. We believe personas are likely to lead to political conflicts and to undermine the ability for researchers to resolve questions with data. We suggest potential research to evaluate the Personas method more thoroughly. Until the methodological issues are resolved, it is best not to consider personas to be a means to communicate data.
The defense response theory implies that individuals should respond to increasing levels of painful stimulation with correlated increases in affectively mediated psychophysiological responses. This paper employs structural equation modeling to infer the latent processes responsible for correlated growth in the pain report, evoked potential amplitudes, pupil dilation, and skin conductance of 92 normal volunteers who experienced 144 trials of three levels of increasingly painful electrical stimulation. The analysis assumed a two-level model of latent growth as a function of stimulus level. The first level of analysis formulated a nonlinear growth model for each response measure, and allowed intercorrelations among the parameters of these models across individuals. The second level of analysis posited latent process factors to account for these intercorrelations. The best-fitting parsimonious model suggests that two latent processes account for the correlations. One of these latent factors, the activation threshold, determines the initial threshold response, while the other, the response gradient, indicates the magnitude of the coherent increase in response with stimulus level. Collectively, these two second-order factors define the defense response, a broad construct comprising both subjective pain evaluation and physiological mechanisms.
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