Detailed analysis and comparison of different activity metrics

Actigraphic measurements are an important part of research in different disciplines, yet the procedure of determining activity values is unexpectedly not standardized in the literature. Although the measured raw acceleration signal can be diversely processed, and then the activity values can be calculated by different activity calculation methods, the documentations of them are generally incomplete or vary by manufacturer. These numerous activity metrics may require different types of preprocessing of the acceleration signal. For example, digital filtering of the acceleration signals can have various parameters; moreover, both the filter and the activity metrics can also be applied per axis or on the magnitudes of the acceleration vector. Level crossing-based activity metrics also depend on threshold level values, yet the determination of their exact values is unclear as well. Due to the serious inconsistency of determining activity values, we created a detailed and comprehensive comparison of the different available activity calculation procedures because, up to the present, it was lacking in the literature. We assessed the different methods by analysing the triaxial acceleration signals measured during a 10-day movement of 42 subjects. We calculated 148 different activity signals for each subject’s movement using the combinations of various types of preprocessing and 7 different activity metrics applied on both axial and magnitude data. We determined the strength of the linear relationship between the metrics by correlation analysis, while we also examined the effects of the preprocessing steps. Moreover, we established that the standard deviation of the data series can be used as an appropriate, adaptive and generalized threshold level for the level intersection-based metrics. On the basis of these results, our work also serves as a general guide on how to proceed if one wants to determine activity from the raw acceleration data. All of the analysed raw acceleration signals are also publicly available.

Verb Second declaratives, assertion, and disjunction revisited

This chapter revisits previous work (Gärtner and Michaelis 2010), which discusses the prospects of theories that derive the distribution of V2-declaratives from their affinity with assertive illocutionary force (potential). It reiterates the challenge disjunctive coordination of V2-declaratives poses to commitment-based contruals of assertion. Likewise, it restates the take on this challenge in earlier work which ‘weakens assertion’ to proposition-level intersection with the common ground. Against the backdrop of this proposal, two recent approaches to the ‘disjunction challenge’ are analysed: (i) a feature-transfer mechanism proposed by Julien (2015), which exempts V2-disjuncts from being directly asserted; (ii) a discourse model developed by Antomo (2016), which discards assertion and, instead, requires the content of V2-declaratives to be relevant to the current question(s) under discussion. The chapter shows that both these approaches run up against serious obstacles, compositionality in the former case, the hard to control flexibility of question-answer relations in context in the latter (among other things). It goes on to conclude that the ‘disjunction challenge’ to accounts of the distribution of V2-declaratives still stands.