Introduction of the tetra-circumplex criterion for comparison of the actual and theoretical structures of the sleep – wake adaptability

In a search for the natural structure of the sleep – wake adaptability, the questionnaire data (total n = 680) were analysed to examine whether the structure of the 72-item Sleep Wake Pattern Assessment Questionnaire (SWPAQ) fits to a theorized circular model. The tetra-circumplex criterion was introduced to measure the extent of deviation of the SWPAQ structure from the structure of the sleep – wake adaptability predicted by the three-dimensional (cube-in-globe) model (Putilov & Putilov 2005 Putilov, A A and Putilov, D A. 2005. Sleepless in Siberia and Alaska: Cross-validation of factor structure of the individual adaptability of the sleep – wake cycle. Ergonomia: An International Journal of Ergonomics and Human Factors, 27: 207–226. [Google Scholar]). The results of the analysis of correlations among the subdimensions of the SWPAQ indicate that these subdimensions might be configured into four two-dimensional circumplex-like shapes. This means that, at least in general, the questionnaire exhibits a clear three-dimensional circumplex structure in accord with the theoretical expectations, and that the deviations from this structure appear to be random. It was concluded that this finding provides empirical evidence of similarity between the actual and theorised structures of the sleep – wake adaptability. Moreover, this finding supports the claim of applicability of the tetra-circumplex criterion for a theoretically based evaluation of structures of chronotypological questionnaires.