Circadian Preference and Amplitude - “Under Consideration of Physiological Markers, Activity and Sleep/Wake Timing as well as References to Attention, Mood and Motivation in Everyday School Life”

Abstract

Morningness-Eveningness can be understood as individual daytime preferences in different physiological, cognitive and behavioral parameters. Those differences can be summarized on the one hand as a dimension of Morningness-Eveningness (continuous) or on the other hand as circadian typology (categorical). Morningness-Eveningness is seen in this case as a uni-dimensional construct, with Morningness and Eveningness marking the two endpoints of one scale. Based on this continuum, the persons were categorized into different chronotype groups. In the meantime, research tends to let go of dividing persons into different chronotype groups. A multi-dimensional view of the construct Morningness-Eveningness is seen instead, whereas a certain type of circadian preference may be more or less pronounced within a person. Research suggests that at least Morningness and Eveningness should be considered as two separate dimensions and other aspects, such as circadian fluctuations over the day, should be include.

Assessing differences in daytime preferences is important, because they have a great impact on the human physiology and health. Especially in school context, adolescents struggle in adapting their inner circadian rhythm to the requirements of our school system. It is known, that morning-oriented adolescents have an advantage over evening-oriented adolescents in terms of sleep habits and school achievement. This is due to the fact that with increasing age, the adolescents tend to describe their selves as more evening-oriented. For this reason a reliable and valid measurement of circadian preference and its stability over the day (amplitude) is needed, which can also be used in an adolescent sample. The measurement used for this purpose in the present dissertation does justice to all of these requirements. The Morningness-Eveningness-Stability scale; improved (MESSi) determines the individual daytime preference and their amplitude. Therefore, the aim of the present dissertation was to validate the measurement MESSi with the help of certain physiological parameters (like body temperature and cortisol) as well as other intervincing variables (like habitual sleep/wake times, activity and personality). On the other hand, the MESSi should be usable in a student population to investigate the influence of Morningness-Eveningness on school-relevant achievement under consideration of important variables in school context (like motivation and mood).