Early birds have the best temperament profile

Here is the abstract from an interesting new study in Personality and Indiviual Differences:

The aim of the present study was to test whether morningness–eveningness is related to the six dimensions of temperament postulated in the Regulative Theory of Temperament: briskness (BR), perseveration (PE), sensory sensitivity (SS), emotional reactivity (ER), endurance (EN), and activity (AC). A sample of 581 undergraduates (age: 21.92 ± 2.54; 381 female) completed the Morningness–Eveningness Questionnaire (MEQ) and the Formal Characteristics of Behaviour – Temperament Inventory. Data was analysed using linear and quadratic hierarchical regressions. The MEQ scores exhibited linear associations with BR and EN and quadratic relationships with PE, ER and AC. Morningness was related to high levels of EN, BR and AC and low levels of PE and ER, while eveningness was associated with low levels of EN, ER, BR and PE and high levels of AC. Subjects in the middle of the morningness–eveningness dimension exhibited high levels of PE and ER, low levels of AC, and average levels of EN and BR. Morningness was related to the most advantageous temperament profile, and temperament is discussed as a possible mediator between morningness–eveningness and mood and affective disorders.

And here are the first two paragraphs:

The morningness–eveningness dimension is a variable belonging to individual differences, describing individual preferences for functioning at various times of the day. Individuals differing in morningness–eveningness display differing circadian phasing of many physiological and psychological circadian rhythms. Individuals with different morningness–eveningness levels also vary in many more individual characteristics than simply their circadian phase position.


Particularly consistent relationships have been shown for morningness–eveningness and affective functioning. Eveningness was associated with a disadvantageous diurnal mood profile, consisting of low energy and pleasance and high tension (Jankowski & Ciarkowska, 2008), which was similar to the profile of individuals with depressive symptoms (Wirz-Justice, 2008). Therefore, it is not surprising that eveningness has been associated with depression (Chelminski, Ferraro, Petros, & Plaud, 1999) and other affective disorders ( [Ahn et al., 2008] and [Murray et al., 2003]). Consequently, greater eveningness was associated with lower life satisfaction (Jankowski, 2012). The above observations seem to have crucial importance in studying morningness–eveningness, as they imply that individual circadian preference may influence key measures of human wellbeing and happiness.

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Owls might look smart, but night owls really are

Here's the conclusion from an interesting research article:

The Savanna–IQ Interaction Hypothesis suggests that more intelligent individuals may be more likely to acquire and espouse evolutionarily novel values and preferences than less intelligent individuals, while general intelligence may have no effect on the acquisition and espousal of evolutionarily familiar values and preferences. An earlier study (Kanazawa, 2010) has shown that more intelligent individuals are more likely to be liberal and atheist, and more intelligent men (but not women) are more likely to value sexual exclusivity, than their less intelligent counterparts. In this paper, we have extended the Hypothesis to circadian rhythms.

While studies show that there is some genetic component to individuals’ circadian rhythms (Hur, 2007), heritability of these phenotypes is far from 1.0 and thus there is room for individual choices and decisions. Survey of ethnographies of traditional societies shows that routine nocturnal activities were probably rare in the ancestral environment and are thus evolutionarily novel. The Savanna–IQ Interaction Hypothesis therefore predicts that more intelligent individuals are more likely to be nocturnal than less intelligent individuals.

Our analysis of Add Health data supports the prediction derived from the Hypothesis. Net of age, sex, race, marital status, parental status, education, earnings, religion, whether one is currently a student and the number of hours worked per week, childhood IQ significantly increases nocturnal behavior in early adulthood. More intelligent children are more likely to grow up to be nocturnal adults who go to bed late and wake up late on both weekdays and weekends (Kanazawa, S., Perina, K. Why night owls are more intelligent. Personality and Individual Differences. 2009).