Chronobiology International The Journal of Biological and Medical Rhythm Research

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Wise “birds” follow their clock: The role of emotional intelligence and morningness–eveningness in diurnal regulation of mood Maciej Stolarski, Konrad S. Jankowski, Gerald Matthews & Justyna Kawalerczyk To cite this article: Maciej Stolarski, Konrad S. Jankowski, Gerald Matthews & Justyna Kawalerczyk (2016) Wise “birds” follow their clock: The role of emotional intelligence and morningness–eveningness in diurnal regulation of mood, Chronobiology International, 33:1, 51-63, DOI: 10.3109/07420528.2015.1115413 To link to this article: http://dx.doi.org/10.3109/07420528.2015.1115413

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Date: 25 January 2017, At: 06:11

CHRONOBIOLOGY INTERNATIONAL 2016, VOL. 33, NO. 1, 51–63 http://dx.doi.org/10.3109/07420528.2015.1115413

ORIGINAL ARTICLE

Wise “birds” follow their clock: The role of emotional intelligence and morningness–eveningness in diurnal regulation of mood Maciej Stolarskia, Konrad S. Jankowskia, Gerald Matthewsb, and Justyna Kawalerczyka a Faculty of Psychology, University of Warsaw, Warsaw, Poland; bInstitute for Simulation and Training, University of Central Florida, Orlando, FL, USA

ABSTRACT

ARTICLE HISTORY

Emotional intelligence (EI) and morningness–eveningness (M-E) preference have been shown to influence mood states. The present article investigates the way in which these two constructs may interact, influencing morning and evening mood levels. A sample of 172 participants completed a multidimensional mood scale measuring energetic arousal (EA), tense arousal (TA), and hedonic tone at 7:00 and at 22:00. As expected, morning and evening types experienced higher EA at their preferred time of day; effects of M-E on other mood dimensions were weaker. EI was found to correlate with lower TA, but the association was stronger at 22:00, perhaps reflecting the role of EI in managing the social events characteristic for the evening hours. An interactive effect of EI and M-E was found for both diurnal changes and morning levels of EA. Namely, in individuals higher in EI, there appeared a more marked synchrony effect between chronotype and EA, which was absent in those low in EI; individuals higher in EI showed more pronounced diurnal changes in EA characteristic for their chronotype (i.e., higher EA at morning hours in morning chronotypes; higher EA at evening hours in evening chronotypes), while in participants low in EI, diurnal changes in EA were smaller. Moreover, the characteristic positive association between morningness and EA during morning hours was apparent only in those high in EI. These findings suggest that individual differences in circadian variation in mood reflect several factors, including an endogenous rhythm in energy, the distribution of social activities throughout the day, and the person’s awareness of their own energy level.

Received 15 July 2015 Revised 28 October 2015 Accepted 29 October 2015

Introduction Morningness–eveningness as determinant of experienced mood

Morningess–eveningness (M-E) preference, also labeled chronotype, is the most widely studied factor within the scope of individual differences in circadian rhythms. M-E is a continuum (Natale & Cicogna, 2002), often divided into morning (scoring highest on M-E dimension), neither, and evening types (scoring lowest on M-E dimension). The latter prefer later than average bed and rise times, function at their peak later in the day (Horne & Östberg, 1976), and report more impaired daytime functioning due to sleepiness (Tonetti et al., 2013) than the former. Evening types also have a later peak in the circadian rhythm of body temperature (Bailey & Heitkemper, 2001). They may also be more vulnerable than morning types to a range of mental and medical health issues (Partonen, 2015), including major depression CONTACT Konrad S. Jankowski © 2016 Taylor & Francis

[email protected]

KEYWORDS

Affect; arousal; chronotype; emotional intelligence; mood; synchrony effect

(Antypa et al., 2015). Such associations may reflect both the biological bases of M-E, such as the lengthened endogenous circadian period in evening types (Partonen, 2015), and psychological factors. Individual differences in chronotype are considered to be a relatively stable trait but mean M-E changes over the lifespan. There is a shift toward eveningness in adolescence (Díaz-Morales et al., 2014), and a steady shift back to morningness throughout the adult years (Jankowski, 2015a). There is also a number of well-established relationships between M-E and other individual difference factors (Adan et al., 2012; Antúnez, Navarro & Adan, 2014). Relationships between M-E and emotional functioning are frequently observed. Studies suggest better overall emotional adjustment in morning types both in adolescence (Díaz-Morales et al., 2015) and in adulthood (Jankowski, 2014). Morning types also exhibit fewer psychopathological symptoms if depressed (Selvi et al., 2010; for review see Adan et al., 2012). On the other hand,

Faculty of Psychology, University of Warsaw, Stawki Str. 5/7, 00-183 Warsaw, Poland.

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research conducted in time-of-day paradigms identify relationships between M-E and mood that vary across the course of the day as mood fluctuates (Adan & Guardia, 1993; Jankowski & Ciarkowska, 2008; Jankowski & Zajenkowski, in press; Matthews, 1988). In general, morningness has been linked to better emotional adaptation, whereas eveningness has been considered as a risk factor for affective disorders (Antypa et al., 2015). For instance, the higher tendency of evening types to consume stimulants (e.g., nicotine; Adan, 1994) may be a symptom of maladaptive coping with lower mood states, characteristic for this group (Peeters et al., 2006). Evening types are also more prone to sleep disturbances (Ong et al., 2007) and to depressive symptoms, such as suicidal thoughts, and impaired work and activities (Gaspar-Barba et al., 2009; Hidalgo et al., 2009). Conversely, subjective wellbeing is higher in morning chronotypes (Jankowski, 2015b). Recently, researchers revealed systematic relationships between emotional and affective temperaments, confirming the claim that evening types are less emotionally adapted than morning and intermediate types (Ottoni et al., 2012). Emotion-regulation processes may contribute to these effects. For example, morning types are more future oriented than evening types; the capacity to delay immediate pleasure and plan for long-term personal success is psychologically beneficial (Stolarski et al., 2013). In addition, associations between M-E and mood may vary across the waking hours of the day, as expected from the definition of the construct of M-E. Diurnal variation of the relationship is rather complex and depends on what mood dimension is taken into consideration (Jankowski & Ciarkowska, 2008). Morningness correlates with better mood in the morning (Díaz-Morales et al., 2015; Jankowski & Zajenkowski, in press; Jankowski & Ciarkowska, 2008), but this relationship is reversed (Matthews, 1988; Thayer et al., 1988) or attenuated (Jankowski & Ciarkowska, 2008; Jankowski & Zajenkowski, in press; Natale & Alzani, 2001) in the evening. Consistent with the general affective advantage for morning types, Jankowski and Ciarkowska (2008) found that these individuals showed better mood for the majority of the day. Positive associations between eveningness and mood in the evening

appear to be more evident for mood dimensions related to alertness and energetic arousal (EA) than for other mood components (Caminada & De Bruijn, 1992; Natale & Alzani, 2001). Emotional intelligence as an influence on experienced mood

John Mayer and Peter Salovey define emotional intelligence (EI) as “the ability to perceive accurately, appraise and express emotion; the ability to access and/or generate feelings when they facilitate thought; the ability to understand emotion and emotional knowledge; and the ability to regulate emotions to promote emotional and intellectual growth” (1997, p. 10). EI may reflect better emotional adaptation (Matthews & Zeidner, 2000), but is also a kind of crystallized intelligence (Mayer & Salovey, 1993). It is typically measured through self-report questionnaires or using ability tests (e.g., Mayer et al., 2002). EI (Gohm, 2003; Mayer & Salovey, 1995) has been linked with mood profiles. The effects of EI are rather intuitive, and EI is even sometimes defined as a variable reflecting effective regulation of moods (Mayer & Salovey, 1995). Stolarski and Bitner (2011) confirmed these expectations, revealing that EI is indeed related to a more adaptive mood profile. Their study was conducted within a framework of three-dimensional model of mood, developed by Matthews et al. (1990), and higher EI proved to be related to lower tense arousal (TA), higher EA, and hedonic tone (HT). Emotional intelligence in chronobiological context

Interestingly, whereas morningness has been linked positively with emotional adaptation, evening types typically score higher on IQ (Preckel et al., 2011; Roberts & Kyllonen, 1999) and inductive reasoning (Díaz-Morales & Escribano, 2013). So far, two studies attempted to determine the relationship between circadian preference and EI. Antúnez et al. (2013) revealed that morningness is related to higher levels of EI, as measured with Trait MetaMood Scale—a self-report scale criticized for not taking into account the “intellectual” character of EI. By contrast, Stolarski and Jankowski (2015)

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applied the ability-based test of EI (Śmieja et al., 2014) and obtained the opposite result: in their two studies higher EI was related to eveningness. These contradictory results show that eveningness is related in the same direction with ability EI as with cognitive intelligence, and in the same manner with the self-reported EI as with self-reported mood. These findings provide additional support for conceptualizing ability EI as the more valid measure of EI (Stolarski & Jankowski, 2015). By contrast, self-report EI may reflect personal beliefs that may not be representative of actual cognitive-emotional skills (Zeidner et al, 2005). Current research investigates, amongst others, how the influence of EI on emotional functioning might vary across the day, beyond any advantage of the person’s chronotype resulting from synchrony effects (i.e., better performance at the preferred time of day; May, 1999). We propose that ability EI may be more influential on emotional functioning later in the day because social activities, whose performance depends on EI, are more common in the evening than in the morning (Larson & Zemke, 2003; Matthews & Harley, 1993). In other words, an effect of ability EI on mood could be actually an outcome of performance in social activities (good mood as a result of rewarding social interactions fostered by higher EI) rather than a direct influence of EI on emotional responses. The above reasoning is supported by studies showing that ability EI is rather weakly related to general emotional response, but is more strongly linked to social adaptation (which is especially important for well-being during evening hours). A meta-analysis (Martins et al., 2010) reported a significant but modest correlation of 0.17 between ability EI and mental health. Similarly, studies of EI and immediate mood show rather small relationships (Matthews et al., 2006). On the other hand, ability EI is more strongly associated (rs < 0.30) with measures of adaptive social functioning such as participation in supportive relationships, lower antagonism toward others, and fewer antisocial behaviors (Brackett et al., 2011; Matthews et al., 2012). With general cognitive ability and personality controlled for, ability EI was associated with socially adaptive/maladaptive behaviors but not with psychological well-being (Rossen & Kranzler, 2009). Given that moods are strongly associated with both positive and negative social encounters (Watson,

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2000) and that ability EI has been consistently linked with elevated quality of social interactions (Lopes et al., 2003), we expect that ability EI may influence mood most strongly in the evening when people have the majority of their interactions with friends and family (Larson & Zemke, 2003). By contrast, M-E measures (e.g., Horne & Östberg, 1976) refer to engagement in mental and physical activity rather than in social interactions. Present study

In the present article, we aimed to take an indepth look into relationships between EI and M-E and their joint influence on morning and evening mood profiles. The research focuses on an ability-based approach to EI referring to the Mayer and Salovey (1997) model, using the Test of Emotional Intelligence (TIE; Śmieja et al., 2014). The study is also based on the three-dimensional model of mood consistent with several psychometric studies (Matthews et al., 1990, 2009; Schimmack & Grob, 2000), although there exist other dimensional models. In common with the model of Thayer (1996), it incorporates two dimensions associated with subjective arousal, experienced either as energy (EA) or tension (TA). A third dimension of HT contrasts pleasant, contented mood with sadness and dissatisfaction. In general, the latter dimension is associated with higher energy and lower tension but constitutes a separate factor in a correlated three-dimensional model (Matthews et al., 1990). Namely, some influences produce effects that are selective to one or other mood dimension, while others induce general changes, associated with higher EA and HT, and lower TA (Matthews et al., 1990). We expected that: Hypothesis 1. EI would better predict more advantageous mood in the evening than in the morning, given that associations between EI and mood may be mediated by more adaptive participation in social activities prevalent in the evening. Hypothesis 2. M-E would be the strongest predictor of EA. Based on the earlier studies (Jankowski & Ciarkowska, 2008; Jankowski & Zajenkowski, in press), we expected that morningness

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would modulate diurnal changes in mood, so that it would correlate with EA in the morning, and this association would be reduced or reversed in the evening. We also expected that morningness would generally correlate with lower TA and higher HT, given the previous findings from time-of-day (Jankowski & Ciarkowska, 2008) and single-measurement occasion studies (Jankowski, 2014; Ottoni et al., 2012). Previous studies suggest that M-E moderates circadian variation in TA and HT only weakly, if at all (Jankowski & Ciarkowska, 2008; Natale & Alzani, 2001).

Hypothesis 3. EI and M-E would have interactive effects on mood. We might expect additive effects of the two constructs, to the extent that M-E is primarily associated with sleep timing, mental alertness, and physical energy (Horne & Östberg, 1976), and EI is primarily related to social functioning (Matthews et al., 2012). However, EI also influences perception and awareness of affective states (Mayer & Salovey, 1997). The primary effect of M-E is on energy (Jankowski & Ciarkowska, 2008; Jankowski & Zajenkowski, in press), but low EI individuals may be unaware of how tired they are in the morning (if evening types) or in the evening (if morning types). Thus, an interactive effect of EI and M-E in different times of day may be hypothesized, with a greater difference between morning and evening types apparent in those high in EI.

Methods Participants

The sample consisted of 103 women and 69 men, aged between 18 and 59 years (M = 25.8, SD = 8.5). The participants were recruited amongst students and students’ families due to the increased availability of these groups to take part in research at relatively extreme times of day. According to the standardization of the Polish MEQ scores, with sex and age adjusted, neither types were defined as these ranging from –1z to 1z based on a large normalization sample (Jankowski & Ciarkowska, 2008). In the present sample, there were 38

morning types, 111 neither types, and 23 evening types. All subjects provided an oral consent to take part in the study; they were not rewarded. The study was conducted according with the ethical standards of the journal (Portaluppi et al., 2010). Measures

EI was measured using TIE (Śmieja et al., 2014). This 24-item ability test was constructed on the basis of Mayer and Salovey’s (1997) four-factor model. Respondents had to read provided descriptions of social interactions. Then, they were required to decide how the protagonists of each situation felt, to select the most effective mode of conduct, or to say which emotions would facilitate and which would interfere with specific task performance. Similar to the Mayer-Salovey-Caruso Emotional Intelligence Test (Mayer et al., 2002), expert scoring criteria were employed to determine the correctness of answers. The TIE responses are scored on four scales, consistent with Mayer and Salovey’s (1997) theory: Perception (Cronbach’s α = .70), understanding (α = .68), assimilation (α = .62), emotion management (α = .60) summing up to general score (α = .88). TIE is a maximum performance test, measuring actual emotional abilities (ability-based EI) and, in contrast to self-report measures, is believed to be independent of self-esteem processes. M-E was assessed using the Morningness– Eveningness Questionnaire (MEQ; Horne & Östberg, 1976) in the Polish adaptation provided by Ciarkowska (Jankowski & Ciarkowska, 2008). Higher scores indicate greater morningness, whereas lower scores indicate greater eveningness. The Cronbach alpha for the Polish adaptation of the MEQ was 0.83 (in the present study: 0.82), while the test–retest reliability was 0.79 at a 6-month interval and 0.84 at 3 months. Mood was estimated using the University of Wales Institute of Science and Technology (UWIST) Mood Adjective Check List (UMACL, Matthews et al., 1990), in the Polish adaptation by Goryńska (2005). The scale has 29 items divided into three subscales measuring: EA, TA, and HT. Respondents rated the degree to which each of the adjectives describes their current mood on a four-point Likert-type scale. In the Polish

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adaptation, the Cronbach alphas for EA, TA, and HT were 0.75, 0.88, and 0.83, respectively. Procedure

The study consisted of three phases. During the first phase, participants completed TIE and MEQ. During that phase specially trained pollsters arranged two further appointments on one of the days in the following week—one in the morning (at 7:00) and one in the evening (at 22:00)—and tested the participants in person to ensure the planned time of measurement is met. During that session, each participant completed a mood scale (UMACL). Scale order was counterbalanced (either 7:00–22:00 or 22:00–7:00). Data were collected in home settings (at university dormitories or private apartments). Statistical analyses

Between-group differences in measured variables were assessed using independent t-tests. Time-ofday effects on mood were analyzed using dependent t-tests. Pearson’s r correlations were calculated to estimate the associations between measured variables. Finally, major hypotheses of the present article were tested using multiple regression analyses including interaction terms. Specifically, we investigated the interactive effects of EI and M-E on mood, at morning and evening hours. For that purpose, we performed a series of regression analyses with M-E, EI, and the M-E × EI interaction term as predictors. The interaction was calculated as the product of the linear terms, using centered predictors. Dependent variables were each mood dimension at the two times of day and mood change scores (Δmood) between evening and morning sessions (evening– morning). All the analyses were performed using IBM SPSS Statistics version 22. Results First, we checked for sex differences in mood dimensions separately for morning and evening session using a series of independent t-tests, which showed no sex differences in three mood dimensions (Table 1). Further, we investigated whether, in the total sample, mood changed between morning and

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Table 1. Between-sex comparisons for mood conducted using independent t-tests. Women M Morning hours (7:00) HT 28.9 TA 16.8 EA 26.7 Evening hours (22:00) HT 30.3 TA 15.7 EA 27.8

Men SD

M

SD

t

df

p

5.2 4.4 6.5

29.8 16.0 26.7

4.2 5.2 5.7

1.20 1.08 0.07

164† 170 170

0.23 0.28 0.95

4.7 4.4 6.2

30.6 15.8 27.9

4.6 4.1 5.7

0.34 0.24 0.11

170 170 170

0.73 0.81 0.92

Note. † Corrected for inequality of variances; HT: hedonic tone; TA: tense arousal; EA: energetic arousal.

evening measurement, using a series of dependent t-tests (see Table 2). The analyses revealed a timeof-day effect only for HT, which was higher in the evening compared to the morning hours. Next, we tested for zero-order correlations between ability-based EI, M-E preference, and the three mood dimensions. Pearson’s correlations revealed that morningness correlated with lower EI (r = −0.16, p < 0.05). Moreover, morningness was related to greater HT and EA and lower TA during morning hours, but during the evening hours this pattern was reversed—morningness was related to lower HT and EA and unrelated to TA (Table 3). EI was only associated with lower TA in the evening. Furthermore, correlations of morningness and EI with diurnal alterations in mood dimensions revealed that EI did not affect the magnitude of mood change from morning to evening hours, but the morningness dimension did. Namely, the more evening oriented individuals were, the greater the increase in EA and HT and the greater the decrease in TA from morning to evening hours they experienced (Figure 1). Regarding regression analyses investigating the interactive effects of EI and M-E on mood at morning and evening hours and mood alteration during

Table 2. Testing significance of differences between average mood levels between morning and evening measurements using dependent t-tests. Morning hours (7:00) HT TA EA

M 29.2 16.5 26.7

SD 4.8 4.7 6.1

Evening hours (22:00) M 30.4 15.7 27.8

SD 4.7 4.2 6.0

t df p 2.60 171 .01 1.87 171 .06 1.50 171 .14

Note. HT: hedonic tone; TA: tense arousal; EA: energetic arousal.

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Table 3. Zero-order correlations between morningness, emotional intelligence, and morning and evening moods.

MEQ EI MEQ EI MEQ EI

HT Morning hours (7:00) 0.23** 0.00 Evening hours (22:00) −0.21** 0.09 Change scores (evening −0.35*** 0.07

TA −0.16* −0.14

EA 0.36*** 0.10

0.13 −0.36*** −0.24** 0.09 hours 22:00–morning hours 7:00) 0.25*** −0.47*** −0.07 0.12

Note. *p < 0.05, **p < 0.01, ***p < 0.001, MEQ: morningness levels, EI: emotional intelligence, HT: hedonic tone, TA: tense arousal, EA: energetic arousal.

a day (Table 4), they extended the results of correlational analyses presented above. Namely, EI was a significant predictor of TA both in the morning and in the evening, even when controlling for the effect of M-E preference. The linear associations between M-E and mood were consistent with those found in the bivariate analyses. Moreover, the results indicated a significant interaction effect between M-E and EI on EA during the morning session and for the daily fluctuations (evening–morning change scores). The moderating role of EI in the relationship between M-E and diurnal fluctuation in EA is presented in Figure 2, where diurnal changes of EA according to chronotype are presented for individuals with different levels of EI (lower 25%, middle 50%, and upper 25% of the sample distribution). It can be observed that the low EI group shows little diurnal variation in EA, irrespective of M-E. However, in medium and high EI groups, diurnal variation in energy appeared in accordance with chronotype (Figure 2). Namely, in more emotionally intelligent individuals, evening chronotypes showed a greater increase in EA from morning to evening hours, whereas morning chronotypes showed decreased EA in the evening. The interaction was primarily driven by the morning data,

Table 4. Predicting mood scores with morningness–eveningness, emotional intelligence, and their interaction. Βeta p Model parameters Hedonic tone (morning hours 7:00) MEQ 0.24 <0.01 R2 = 0.07 EI 0.02 0.83 F(3,168) = 3.9 MEQ × EI 0.12 0.13 p < 0.01 Hedonic tone (evening hours 22:00) MEQ −0.21 <0.01 R2 = 0.05 EI 0.06 0.41 F(3,168) = 2.9 MEQ × EI −0.02 0.79 p < 0.05 ΔHedonic tone (evening hours 22:00–morning hours 7:00) MEQ −0.35 <0.001 R2 = 0.13 EI 0.04 0.63 F(3,168) = 9.2 MEQ × EI −0.11 0.14 p < 0.001 Tense arousal (morning hours 7:00) MEQ −0.20 <0.05 R2 = 0.06 EI −0.16 <0.05 F(3,168) = 3.5 MEQ × EI −0.06 0.45 p < 0.05 Tense arousal (evening hours 22:00) MEQ 0.10 0.21 R2 = .07 EI −0.24 <0.01 F(3,168) = 4.3 MEQ × EI 0.08 0.29 p < .01 ΔTense arousal (evening hours 22:00–morning hours 7:00) MEQ 0.25 <0.001 R2 = .08 EI −0.05 0.54 F(3,168) = 9.2 MEQ × EI 0.12 0.13 p < .001 Energetic arousal (morning hours 7:00) MEQ 0.37 <0.001 R2 = 0.18 EI −0.08 0.30 F(3,168) = 12.0 MEQ × EI 0.21 <0.01 p < 0.001 Energetic arousal (evening hours 22:00) MEQ −0.36 <0.001 R2 = 0.14 EI 0.05 0.53 F(3,168) = 9.2 MEQ × EI −0.10 0.20 p < .001 ΔTense arousal (evening hours 22:00–morning hours 7:00) MEQ −0.47 <0.001 R2 = 0.26 EI 0.08 0.26 F(3,168) = 9.2 MEQ × EI −0.20 <0.01 p < 0.001 Note. MEQ: morningness levels; EI: emotional intelligence.

given that interaction failed to reach significance in the evening, although Figure 2 shows a trend toward a reversal of the association between M-E and EA in the higher EI groups only. Figure 3 provides a more detailed rendering of the M-E × EI interaction at 7:00 in the morning. To illustrate the interaction, the regression lines presenting associations between M-E and morning energy were

Figure 1. Diurnal changes in hedonic tone (panel A), tense arousal (panel B), and energetic arousal (panel C) in morning (squares, solid line, n = 38), neither (triangles, dashed line, n = 111), and evening (circles, dotted line, n = 23) chronotypes.

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Figure 2. Diurnal changes in energetic arousal in morning (squares, solid line), neither (triangles, dashed line), and evening (circles, dotted line) chronotypes depending on the levels of emotional intelligence.

Figure 3. Relationship between morningness (MEQ) and energetic arousal at 7:00 in the morning in individuals with high EI (triangles, solid line), medium EI (squares, dotted line), and low EI (circles, dashed line).

fitted in subgroups distinguished based on EI scores (lower 25%, middle 50%, and upper 25% of the sample distribution). All three EI groups show a positive association between morningness and EA, as expected. However, the slope of the plot, representing the strength of the association, increases as EI increases. In other words, morningness better predicts higher morning EA in those individuals who are higher in EI. To sum up the interactive effects of M-E and EI on EA, higher EI facilitates mood following the circadian rhythm of energy appropriate for the person’s level of M-E. On the contrary, in people with low EI, the impact of M-E on diurnal variations in mood is less pronounced.

Discussion Personal characteristics, including M-E and EI, may exert both general influences on mood, happiness and wellbeing, and influences that are dependent on time of day. This study demonstrated both types of effect, although with circadian effects predominating. As expected, ability EI was associated with better mood, in the form of lower TA, although the relationship was stronger in the evening than in the morning hours. Moreover, morningness was associated with lower EI, as recently reported by Stolarski and Jankowski (2015) (see the discussion of Hypothesis 1).

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Although most reports indicate that morningness is generally related to better emotional adaptation (Díaz-Morales et al., 2015; Jankowski & Ciarkowska, 2008; Ottoni et al., 2012), we found that this may be true in the morning, but during late evening hours evening chronotypes surpass morning types in EA and HT (see the discussion of Hypothesis 2). We also found that predictors of mood varied across time of day. Overall, it can be concluded that M-E makes people feel better in their optimal part of the day (morning for “larks” and evening for “owls”), while the benefits of EI in reducing tension are more apparent in the evening. These associations between M-E and mood reversed in sign between morning and evening and are consistent with general expectation (Jankowski & Ciarkowska, 2008). As also expected, the interaction between time of day and M-E appeared to be strongest for the EA dimension of mood. However, there was a further moderator effect of EI in the morning. The association between morningness and higher energy in the morning is well substantiated in previous studies (Adan & Guardia, 1993; Jankowski & Ciarkowska, 2008; Jankowski & Zajenkowski, in press; Matthews, 1988; Thayer et al., 1988). However, our data suggest that the association is more robust in individuals who are higher in EI (see the discussion of Hypothesis 3). In the remainder of the discussion, we will examine the relationships found in more detail, in relation to the study hypotheses. We will also outline the study limitations and suggestions for further research.

If TA tracks stressful events rather than endogenous rhythms (Murray et al., 2009), its negative association with EI may broadly reflect the better stress management of emotionally intelligent individuals (Matthews et al., 2012). However, the greater strength of the association in the evening may be a consequence of the competency that those high in EI appear to possess for managing social encounters (Brackett et al., 2011), which are more prevalent in the evening. By contrast, high EI does not relate to any special facility in coping with nonsocial stressors such as workload and monotony (Matthews et al., 2006). Although eveningness seems to be emotionally maladaptive (Jankowski, 2014; Ottoni et al., 2012), greater eveningness is related to greater ability EI (Stolarski & Jankowski, 2015). We might speculate that evening types experience a more intensive social life which affords more practice in developing emotional competencies. Alternatively, the emotional challenges of functioning throughout the day as an evening type may promote a compensatory increase in EI. Moreover, EI was unrelated to positive affect dimensions including EA and HT, consistent with previous studies of ability EI and subjective state (Fallon et al., 2014; Matthews et al., 2006). EI has been characterized as a key trait for positive psychology (Salovey et al., 2009), promoting well-being, and thus it might be surprising that ability EI is not a stronger predictor of positive mood than M-E. A resolution to the paradox is suggested by Extremera et al. (2011) who concluded that EI is more strongly related to “eudaimonic” well-being (personal growth and fulfillment) than to hedonic well-being, which is more directly expressed in positive mood.

Emotional intelligence and mood (Hypothesis 1)

We confirmed the expectation that ability EI should be more strongly associated with better mood in the evening than in the morning (Hypothesis 2), for the TA dimension only. The magnitudes of the significant EI—tension correlation was modest (<0.30), in line with the small but non-zero association between ability EI and mental health reported by Martins et al. (2010), and a –0.29 correlation between ability EI and subjective distress found in an experimental study of human performance (Matthews et al., 2006).

Morningness–eveningness and mood (Hypothesis 2)

The results supported hypothesis 1, consistent with two of the principal findings of previous research— the sensitivity of EA to individual differences in M-E and the more limited impact of M-E on TA. The findings on M-E and EA are similar to those reported in several previous studies (e.g., Caminada & De Bruijn, 1992; Jankowski & Zajenkowski, in press; Matthews, 1988) and subjective alertness ratings (Natale & Alzani, 2001). Thus, they confirm the notion that individual differences in M-E play

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out most directly in relation to energy (Jankowski & Zajenkowski, in press). The magnitude of the M-E– energy correlation was similar at both times of day, but reversed in sign—an observation not always present in previous research (Jankowski & Ciarkowska, 2008; Jankowski & Zajenkowski, in press). It may be concluded that evening chronotypes exhibit greater EA than morning chronotypes if measurement is taken at 22:00 or later (as in the present study), while during the earlier hours there are no differences between chronotypes or morning types show affective advantage from morning to afternoon hours (Jankowski & Ciarkowska, 2008; Jankowski & Zajenkowski, in press). Energy may constitute a marker for the reward or behavioral activation system of the brain (Matthews et al., 2009). Its sensitivity to M-E may then reflect the pronounced endogenous circadian variation in reward system activation demonstrated in studies of positive affect (Murray et al., 2009). The present study suggests that similar individual differences may be expressed in HT as well, although in a previous study with more measurement points throughout the day HT did not strictly follow EA (Jankowski & Ciarkowska, 2008). However, Caminada and De Bruijn (1992) showed that time of day changes in pleasantness of mood (similar to HT) differed between chronotypes, even with variation in EA controlled. Thus, HT may follow EA in some circumstances, but not in others, as discussed by Jankowski and Ciarkowska (2008). Morningness was significantly correlated with lower tension in the morning, but a small positive correlation between the trait and tension in the evening was non-significant. These results may reflect that in evening chronotypes TA decreased from morning to evening hours, whereas in morning types TA remained at a similar level on the two measurement occasions (see Figure 1). Overall, this is the first study reporting diurnal trends in TA differing between chronotypes. An effect of morningness on morning but not evening levels of TA was reported previously (Jankowski & Zajenkowski, in press), whereas in another study, diurnal trends in tension did not appear to show marked differences between morning and evening types (Jankowski & Ciarkowska, 2008). Taken together, these results support a suggestion that circadian

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trends in TA may be subject to exogenous factors (Jankowski & Ciarkowska, 2008) given the lack of an endogenous circadian rhythm in the brain punishment systems that influence negative affect (Murray et al., 2009). The general associations between eveningness and more negative mood reported in some studies may also be more evident in the middle part of the day (Jankowski, 2014). Interactive effects of emotional intelligence and morningess–eveningness on mood (Hypothesis 3)

The research literatures on the impacts of EI and M-E on mood have developed separately from each other. Thus, it is intriguing to find that the two factors had an interactive effect on EA. The results showed that in individuals high in EI there was a synchrony effect (May, 1999) between chronotype and EA—a more pronounced daily change in mood in accordance with chronotype. On the contrary, individuals low in EI had a flat profile of diurnal change in EA, regardless of chronotype. Given that sleepiness, fatigue, and alertness—core components of EA—are driven endogenously as they parallel core body temperature (Schmidt et al., 2007), it could be concluded that individuals high in EI are more in tune with their own physiology. In other words, more emotionally intelligent people better follow their circadian rhythm, e.g., in the morning high EI larks are even more energetic, and high EI owls are even more sleepy. Thus, EI seems to enhance endogenously driven energy levels. Conversely, people low in EI may show less daily changes if they try to compensate for feelings of over- or under-arousal using external agents, e.g., psychostimulants. Indeed, low EI has been related to increased use of psychoactive substances (Riley & Schutte, 2003; Trinidad & Johnson, 2002), while M-E was a better predictor of consumption of psychostimulants than personality traits (Adan, 1994). The interaction is also consistent with the hypothesis that emotionally intelligent individuals should have more awareness of their moods, and so should be better able to report circadian variation. A possible explanation of the more pronounced morning interaction effect and its absence in the evening is that a lack of self-awareness of energy is specifically

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tied to sleep inertia, the period of confusion, and impaired cognitive function that accompanies the transition from sleep to wakefulness (Marzano et al., 2011). High EI may be particularly needed during this period in order to report accurately on one’s level of energy. Limitations and further directions

Three study limitations suggest further directions for research. First, substantiating some of the explanations we have given for the observed outcomes requires testing over the course of the day, and not only at two times early and late. Testing at multiple times allows circadian rhythms to be more precisely mapped for individuals or groups varying in M-E and EI. Such mapping may be necessary to demonstrate the association between eveningness and more negative mood (e.g., Jankowski & Ciarkowska, 2008; Díaz-Morales et al., 2015). Also, the “sleep inertia” explanation proposed for the morning M-E × EI interaction predicts that the interaction should not persist beyond the first hour or so of wakefulness. Second, the current design did not allow for measurement or control of the person’s activities, which might be important given the hypothesized role of engagement in social activities. We assumed that the evening association between EI and lower TA would be moderated by the person’s engagement in social activities. EI may have little impact on mood if a person stays home and watches TV alone. Given that eveningness is related to greater propensity to stay out late (Randler et al., 2012), it would also be interesting to check how EI interacts with M-E in the person’s choice of whether to seek social activity in the evening. Would morning types high in EI be more confident of overcoming evening fatigue? Or would these individuals be more accepting of their circadian physiology and choose rest over activity in the evening? An experience sampling design (e.g., Miller et al., 2015) might be adopted to address such questions. Third, understanding the functional significance of mood variation may require attention to cognitive and motivational variables as well. To understand whether morning and evening

types are functionally emotionally intelligent at different times of day, cognitive competencies and motivations should also be assessed. For example, Carciofo, Du, Song, and Zhang (2013) found that higher levels of mind wandering, daydreaming, and attention-related cognitive errors appear at the non-preferred time of day, implying that challenging social encounters occurring in evenings may be objectively more difficult to negotiate for morning types. Such evidence may be important for assessing how individual differences in mood at different times of day are linked to adaptive outcomes. Finally, in the study, a convenience sample was used, which produced slight overrepresentation of women and a relatively wide age range. Future studies should replicate the results in a more sex-balanced sample and test in a larger sample whether age moderates the relationships found here. A larger sample size would also increase the generalizability of the results and would allow testing of additional hypotheses, for instance regarding sex differences. Nevertheless, it was large enough to ensure adequate power to detect hypothesized effects and was large compared to some other studies conducted in the time of day paradigm (e.g., N = 96; Fabbri et al., 2008). Moreover, the role of personality traits could be elucidated in future research as some of those related to chronotype may also be involved in regulation of affect (Muro et al., 2009; 2011). For example, morning types tend to have more conscientious personalities (Tonetti et al., 2009), which may be more adaptive for work activities (Muro et al., 2009), occurring mostly in the first part of the day, but less adaptive for unstructured social interaction, occurring more in the evening. Conclusions Both M-E and EI are important for mood, but their effects may be more subtle than is sometimes appreciated. Time-of-day alterations may reflect individual differences in both endogenous circadian rhythm, influencing energy and alertness, and in competency in managing social encounters, influencing tension and stress. It is expected that morning and evening types experience more

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positive moods at their preferred time of day, but, in fact, the association between M-E and mood depends on the mood dimension assessed, and may be stronger in the morning than in the evening for some dimensions. It is also expected that high EI confers better mood, but the benefits of EI are more apparent in reduced evening tension than in general elevation of mood. EI may also moderate the association between M-E and energy, so that synchrony effect between chronotype and mood is particularly well observed in those high in EI. Further understanding of these associations requires attention to the context in which mood is assessed, and its functional significance for the person at different times of day. Declaration of interest The authors declared no conflict of interests. This work was supported by a grant DEC-2011/03/D/HS6/05760 from the National Science Centre, Poland.

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