Daily transformational leadership: A source of inspiration for follower performance?

This study uses the full-range leadership model to argue that on days when leaders engage in transformational leadership behaviors, they identify follower strengths and stimulate followers to show personal initiative. We propose that transformational leadership is related to follower work engagement and performance through follower strengths use and personal initiative. Moreover, we hypothesize that followers ’ personal initiative is most effective when followers use their strengths. A total of 57 Norwegian naval cadets filled out a diary booklet for 30 days (response = 72.6%; n = 1242). Multilevel modeling analyses largely supported our hypotheses. On the days when leaders used transformational leadership behaviors such as intellectual stimulation and individual consideration, followers were more likely to use their strengths and take initiative. These behaviors, in turn, predicted next-day work engagement and next-day job performance. Moreover, followers ’ personal initiative was particularly related to work engagement when strengths use was high rather than low. We discuss how these findings contribute to the leadership literature by showing how leaders inspire their followers to lead themselves. In addition, we elaborate on the practical implications for leadership training.

The quintessence of leadership is the ability to influence and motivate other people.How do effective leaders get followers excited and dedicated to their course of action?Research has revealed a broad array of leadership traits and styles that are related to follower attitudes, motivation, and performance.One influential approach is the full-range leadership model (Bass, 1985).Accordingly, transactional leaders lead through social exchange; for example, they lead by exchanging rewards and recognition for creative ideas and productivity.In contrast, transformational leaders are persons who show individual consideration to followers and inspire them to be at their best and develop their own leadership skills (Bass & Riggio, 2006).Although more recent research has shown that effective leaders also show instrumental leadership (e.g., scan the internal and external environment, set goals, and provide job resources; Antonakis & House, 2014;Breevaart & Bakker, 2018), meta-analyses have clearly shown that employees who interact with transformational leaders are more satisfied and motivated and perform better (Hoch, Bommer, Dulebohn, & Wu, 2018;Wang et al., 2011).However, what remains unclear is how (i.e., through which employee behaviors) transformational leaders gain their influence and motivate their followers to be engaged in their work.
In the present study, we integrate transformational leadership theory with job demands-resources (JD-R) theory (Bakker & Demerouti, 2018;Bakker & Van Woerkom, 2017) to investigate more precisely what it is in their followers that effective leaders transform.Are followers indeed inspired to lead themselves when leaders engage them in a transformational leadership style?Previous research has assumed that transformational leadership leads to transformations in followers-i.e., changes in their behaviors and, consequently, their attitudes and performance.In the present study, we empirically show that when leaders are transformational, they encourage their followers to engage in proactive behaviors.Specifically, we propose that when leaders engage in transformational leadership, they identify follower strengths and stimulate followers to (a) use their strengths and (b) take personal initiative.Such behaviors may foster work engagement-an affective motivational state characterized by high levels of energy (vigor), enthusiasm about work (dedication), and full immersion in work activities (absorption; Schaufeli & Bakker, 2010).When employees use their strengths and take personal initiative, they do what they are already good at and apply a self-starting approach to their work goals and tasks.JD-R theory proposes that through such an approach, employees will generate job and personal resources, such as autonomy, skill variety, and self-efficacy (Bakker, 2017).These resources can be used to deal with job demands and will indirectly contribute to work engagement and performance.
We aim to make four contributions.First, we expand leadership and JD-R theories by studying the processes through which transformational leadership takes effect.We argue that leadership indicated by idealized influence, inspirational motivation, intellectual stimulation, and individual consideration encourages followers to use their strengths and take personal initiative-two behaviors that fuel work engagement and performance.By investigating active follower behaviors, we clarify the role of followers in the leadership process.Second, we contribute to strength theory by proposing a crucial predictor of strengths use.Previous research has primarily focused on the possible consequences of strengths use, including self-efficacy, positive affect, work engagement, and performance (Bakker & Van Woerkom, 2018).In the present study, we examine a potentially important antecedent in the work context-namely, transformational leadership.Third, we contribute to proactive behavior theory by studying the role of the leader and by investigating when personal initiative is most likely to foster work engagement and performance.We propose that personal initiative is most effective when employees actively use their strengths.Finally, we take a daily diary perspective and follow naval cadets from day to day during their journey from Northern Europe to the US over the course of a full month.Although several studies have used a within-person perspective to study leadership, the vast majority of studies have used a between-person design to uncover who are the best leaders.We take a new perspective and propose that all leaders can make a difference in followers' performance when they enact transformational leadership behaviors.

Theoretical background
Transformational leadership denotes the process of a leader motivating followers to strive for group versus personal goals through charisma, inspirational motivation, intellectual stimulation, and/or individualized consideration (Bass, 1985).Charisma or idealized influence refers to followers' admiration for their leader, who provides a clear vision and purpose and serves as a positive role model.Charismatic leaders communicate symbolically and persuade followers that their vision entails a bright future for the organization (Antonakis, 2012).Inspirational motivation is the ability of leaders to inspire and motivate followers to reach ambitious goals.Through their optimism and enthusiasm, leaders inspire followers to feel confident that they will succeed.The third dimension, intellectual stimulation, involves challenging followers' assumptions and soliciting ideas from followers without criticism.Leaders who enact this form of leadership help change the way followers frame and think about obstacles and problems.Finally, individual consideration refers to leaders' support for and coaching of, frequency of interaction with, and help offered to their followers to maximize their potential by using their strengths.Leaders who use this form of leadership have an eye for individual needs and wishes and acknowledge that each follower is unique.Thus, transformational leadership involves a range of leader behaviors that have the potential to "transform" followers and positively influence their work engagement.
Research in recent decades has provided considerable evidence for the effectiveness of transformational leadership (Judge & Piccolo, 2004;Wang et al., 2011).However, the transformational leadership approach has been criticized for embedding some of the intended leader effects in the concept itself, thus making the argument tautological (Van Knippenberg & Sitkin, 2013).In the present study, we largely circumvent this problem by asking for concrete, daily leadership behaviors without reference to the possible effects of these behaviors.These daily leader behaviors are then linked to daily follower behaviors, work engagement, and colleague ratings of performance.Using this procedure, we investigate the behavioral mechanism through which leaders try to make followers excited and dedicated to their course of action.
Combining leadership and JD-R theories (see also Tummers & Bakker, 2021), we argue that when leaders engage in transformational leadership, they motivate followers to proactively generate their own job challenges and job resources, which are the most important predictors of work engagement (Bakker & Demerouti, 2017, 2018).By taking initiative and capitalizing on personal strengths, employees can optimize their work design and approach so that they can be engaged and perform well.There are some diary studies showing favorable links between transformational leadership and follower work engagement, but diary research on a direct link between transformational leadership and follower behaviors is largely missing.Tims et al. (2011) followed a heterogeneous group of employees for five working days and found that employees were most engaged on days when their leaders acted transformationally; this effect was mediated by optimism, an important personal resource.Breevaart et al. (2014) used a 34-day diary study and found that daily manifestations of transformational leadership behaviors encouraged follower engagement through daily job resources such as autonomy and social support.Taken together, these findings indicate that when leaders show transformational leadership behaviors, they provide both personal and job resources to their followers.Furthermore, Breevaart et al. (2016) used a weekly diary study to show that weekly transformational leadership behaviors were positively related to weekly supervisor ratings of follower job performance through weekly follower work engagement.These effects were most pronounced during weeks followers needed their leaders most-for example, when they were confronted with ambiguous challenges and high work pressure (see also Breevaart & Bakker, 2018).
While these previous diary studies have shown that transformational leadership may generate personal and job resources and hence help followers deal with job demands and be engaged, the precise employee behaviors through which transformational leadership is related to follower work engagement and performance remains unclear.Building on JD-R theory (Bakker & Demerouti, 2018;Bakker & Van Woerkom, 2017) and expanding previous research linking JD-R and leadership (Tummers & Bakker, 2021), we argue that leaders influence follower engagement and performance via their impact on follower strengths use and follower personal initiative.

Strengths use and personal initiative
Character strengths refer to the capability to think, feel and behave such that one can function optimally when striving for valued outcomes (Linley & Harrington, 2006).Examples of such strengths are curiosity, self-control, humor, and bravery.Although strengths are trait-like, their positive psychological consequences are particularly experienced when individuals identify and enact their strengths (Peterson & Seligman, 2004;Van Woerkom, Oerlemans, & Bakker, 2016).When people use their strengths, these strengths are vitalizing and allow a person to thrive (Dubreuil et al., 2014;Wood et al., 2011).In sharp contrast, when individuals try to improve their weaknesses, they may feel discouraged (Hodges & Clifton, 2004).Bakker et al. (2019) showed that employees were most engaged in their work on days when they actually used their strengths; this effect was most pronounced for emotionally stable and extraverted employees.Bakker (2017) integrated strengths use in JD-R theory and argued that when employees use their strengths, they generate job and personal resources.A central proposition in JD-R theory is that such resources can be used to deal with job demands to stay engaged and perform well (Bakker & Demerouti, 2017).
Personal initiative refers to applying a proactive approach to work goals and tasks-behavior that is characterized by persistence in overcoming barriers and setbacks (Frese & Fay, 2001).Employees may take personal initiative to prevent work-related problems or when they anticipate and prepare for future demands.In this way, they proactively optimize their job demands (e.g., Tims & Bakker;Demerouti & Peeters, 2018).Moreover, personal initiative may take several forms, such as seeking feedback, asking for support, developing plans to deal with future job demands, or searching for ways to change the work situation (Parker & Collins, 2010).Thus, from a JD-R theoretical perspective, employees who take personal initiative create their own challenge job demands and actively seek job resources.This proactive behavior is important because modern workplaces require a considerable degree of self-reliance (Campos et al., 2017).Proactive behavior is more generally defined as anticipatory and active behavior employees engage in so that they change themselves or their environment (Grant & Ashford, 2008).When employees take personal initiative, they are agentic, mindful, and anticipatory-they consciously want to change things and have an impact (Den Hartog & Belschak, 2012. p. 195).Meta-analyses have shown that personal initiative is predictive of satisfaction, organizational commitment, social networking behavior, and job performance (Thomas et al., 2010).

The present study
When leaders are transformational, they acknowledge the unique knowledge, abilities, and skills of their followers (i.e., individual consideration).Therefore, when enacting transformational leadership, leaders are most likely to identify their followers' strengths.By expressing high expectations and confidence in their followers and acting as a positive role model (i.e., projecting inspirational motivation and idealized influence), such leaders encourage followers to use their personal strengths and be at their individual best.Moreover, transformational leadership includes challenging obvious ways of working (i.e., providing intellectual stimulation) and thus may encourage followers to use their strengths in totally new ways.When individuals use their strengths, they can be authentic and behave in accordance with their values, preferences, and needs (Peterson & Seligman, 2004).They are therefore more likely to be engaged and show healthy psychological and interpersonal functioning (Kernis & Goldman, 2006).Moreover, strengths use leads employees to experience mastery and feelings of self-efficacy (Bakker & Van Woerkom, 2018) and will therefore enhance work engagement.Hence, we propose: Hypothesis 1. Daily transformational leadership relates positively to next-day work engagement through daily employee strengths use.
In addition to promoting strengths use, we argue that transformational leadership behavior also promotes followers' personal initiative by indirectly increasing their work engagement.Transformational leaders use charisma tactics to communicate an appealing vision of the future and articulate high-performance expectations (Antonakis et al., 2011).Such leaders inspire followers by providing clear challenges and by vividly explaining the importance and meaning of engaging in shared goals.Followers who interact with such leaders become motivated and committed to achieving results (e.g., Bass, 1985).In addition, a major goal of transformational leaders is to motivate followers to lead themselves (Avolio & Gibbons, 1988).Transformational leaders encourage followers to think creatively and independently (Bass & Avolio, 1990) and facilitate proactive behavior by empowering employees and motivating them to apply new techniques to their work (Den Hartog & Belschak, 2012;Schmitt et al., 2016).Indeed, a recent study among Norwegian knowledge workers showed that followers were more likely to be proactive (e.g., ask for performance feedback, seek social support) on days when their leaders show transformational leadership (Hetland et al., 2018).When followers take personal initiative, they are agentic, change what they find important, and garner their own resources.JD-R theory proposes that when employees proactively mobilize their job and personal resources, they increase their own work engagement (Bakker & Demerouti, 2017;Tummers & Bakker, 2021).Thus, we hypothesize: Hypothesis 2. Daily transformational leadership relates positively to next-day work engagement through daily employee personal initiative.
Next, we argue that transformational leadership particularly influences follower work engagement when followers are encouraged to use their strengths when they are proactive.Thus, we argue that the combined effect of strengths use and personal initiative will have the most positive impact on engagement.When individuals take initiative, they plan for and anticipate a different future.Personal initiative may take the form of seeking feedback, voicing concerns, or searching for ways to optimize the work situation (Parker & Collins, 2010).Such initiatives are most likely to be effective on days when individuals use their personal strengths.For example, through social competence, employees may be better able to proactively garner social resources.Colleagues may be more willing to share resources with an employee who shows emotional concern and is able to take other perspectives.As another example, bravery-one other possible strength (Peterson & Seligman, 2004)-may be especially important when naval cadets-the sample under study-proactively deal with high challenge job demands, such as when climbing the rigs or sailing the vessel in rough weather.In contrast, when individuals take initiative while capitalizing on their weaknesses, they are more likely to fail and thus undermine their own engagement (Bakker & Van Woerkom, 2017).In short, personal initiatives may be more successful when individuals use their strengths, which may then fuel people's enthusiasm, energy, and absorption (i.e., work engagement).
Hypothesis 3a.The relationship of daily personal initiative with nextday work engagement is qualified by strengths use.This relationship is more positive for employees who show high rather than low levels of daily strengths use.

Hypothesis 3b.
The indirect relationship of daily transformational leadership with next-day work engagement through employee personal initiative is stronger for employees who show high rather than low levels of daily strengths use.
Finally, expanding upon previous research providing evidence for a link between daily/weekly transformational leadership, engagement, and performance (Amor et al., 2020;Kelemen et al., 2020), we argue that daily transformational leadership is related to follower performance first through follower behaviors (strengths use and personal initiative) and then through follower work engagement (cf.Bakker & Demerouti, 2018;Tummers & Bakker, 2021).Thus, as delineated in Fig. 1, we propose that daily transformational leadership has implications for follower performance because such leadership behaviors inspire followers to use their strengths, be agentic, and lead themselves.This experience of taking charge and feeling empowered by the leader will energize and enthuse employees (i.e., enhance work engagement), which is crucial for daily performance.

Participants and procedure
We invited 66 naval cadets from a Military University College in Norway to participate in this study.All cadets finished leadership training, which included sailing a large vessel from Northern Europe to New York.The study was conducted between September and November 2017.Of the 66 invited cadets, 57 completed the survey, yielding an overall participation rate of 86.4%.Participants were kindly requested to fill out short diary surveys just before supper at 5 p.m. each day on 30 consecutive days.At this time of day, all cadets are awake and no one is asleep.The cadets were assigned to eight different teams, and every few days, there was a change in who acted as the squad leader (i.e., the hierarchical positions change).Cadets were therefore asked to rate the leadership behaviors of their acting immediate superior that day.The interchange of acting leaders resolved in an ICC1 of 0.271, indicating that 72.9% of the variance in exposure to transformational leadership behaviors is explained at the within-person level.To facilitate a good response rate, each squad leader was asked to encourage their squad to fill out the survey.The daily response rate was strong, with an average of 72.6% (the total number of observations was 1242 out of 1710).The sample included 50 males (87.7%), six females (10.5%), and one individual who did not identify gender (1.8%).The sample was relatively young (mean age = 22.9 years, SD = 2.2).

Measures
All study variables were measured using short daily surveys.The surveys included adapted versions of existing and validated instruments.We modified the time frame of the items so that each statement referred to that day only.In line with recommendations for diary research (Ohly et al., 2010), we also reduced the length of each measurement scale so that participants could respond to all items on a daily basis.
Daily transformational leadership was assessed using seven items from the global transformational leadership (GTL) scale (Carless et al., 2000).In their validation research, the authors showed that GTL correlated positively and substantially (on average .85)with the various dimensions of the leadership practices inventory (Kouzes & Posner, 1990) and the multifactor leadership questionnaire (Avolio, Bass, & Jung, 1999).Examples are "Today, my leader gave encouragement and recognition to staff" and "Today, my leader encouraged thinking about problems in new ways and questioned assumptions."Participants were asked to indicate the extent to which they agreed with these statements (1 = totally disagree; 5 = totally agree).The reliability of the scale was good.Across the 30 days, Cronbach's α was 0.84 on average.Daily personal initiative was assessed with 4 items based on Frese et al. (1997): "On today's shift, I have taken initiative immediately, even when others did not" (1 = totally disagree; 5 = totally agree).The average Cronbach's α was 0.81.
The average Cronbach's α was 0.91.Day-level job performance was measured by asking colleagues to rate the focal employee's job performance.Two or three colleagues rated each cadet during each of the 30 days using four adjusted items from Goodman and Svyantek's (1999) performance scale.The raters were the same individuals throughout the whole study period.Example items are: "Today, the cadet has achieved the objectives of his or her job" and "Today, the cadet has fulfilled all the requirements of his or her job" (1 = totally disagree; 5 = totally agree).To estimate inter-rater agreement, we calculated the average deviation index (Burke & Dunlap, 2002) for the scale across the 30 days.The average score for this index was 0.17, indicating high inter-rater agreement.

Strategy of analysis
Since the 30 daily assessments (level 1) of the study variables were nested within individuals (level 2), we conducted multilevel analyses using Mplus 7.4 (Muthén & Muthén, 1998-2012).Before running any analyses, all day-level (level 1) predictors were centered on the person mean.Furthermore, work engagement was modeled as a latent construct using the three subscales of vigor, dedication, and absorption as indicators, while all other study constructs were modeled using their respective observed scores.The hypothesized prospective model is illustrated in Fig. 1.In the within part of the model, the main predictor (transformational leadership), the initial mediators (strengths use and personal initiative), and the interactional effect between strengths use and personal initiative were modeled on the same day (k), while work engagement and second source job performance were modeled on the following day (k+1).At the between-level analysis, the latent factors of work engagement and job performance were allowed to covary.The fit of the model was determined with the following indices: chi-square, comparative fit index (CFI), Tucker-Lewis index (TLI), root mean square error of approximation (RMSEA), and standardized root mean  square residual (SRMR).The significance of the indirect effects by estimation of confidence intervals was obtained within the Mplus program.Subsequent to testing the multilevel models, we conducted simple slope tests for multilevel models to test whether the slopes of the interactions differed significantly from zero (Preacher et al., 2006).The slopes were tested at ±1 SD for the predictor (personal initiative) and moderator (strengths use).We used R version 3.4.3,and calculations were based on the asymptotic covariance matrix of the multilevel models.

Descriptive statistics
The means, standard deviations, and correlations can be found in Table 1.

Multilevel models
Calculations of interclass correlations prior to testing the multilevel model revealed a correlation of 0.42 for second source job performance, showing that 58% of the variance in performance exists on the daily level (within-level), allowing us to continue with the multilevel analysis.Testing the hypothesized multilevel model revealed excellent fit to the data (χ 2 = 10.76,df = 15, CFI = 1.00,TLI = 1.00,RMSEA = 0.000, SRMR-within = 0.014, SRMR-between = 0.021), supporting the overall validity of the model.Fig. 2 presents the standardized parameter estimates in the model.As seen in the figure, there are significant associations between transformational leadership and both initial mediators (β = 0.11, p < .01 and β = 0.17, p < .01 for personal initiative and strengths use, respectively).Moreover, there is also a significant association between transformational leadership and the strengths use × personal initiative interaction term (β = .07,p < .05).Strengths use (β = 0.10, p < .01),personal initiative (β = 0.08, p < .05),and the interaction term (β = 0.07, p < .05) each predict next-day work engagement.Finally, in the overall model, next-day work engagement is positively related to nextday job performance (β = 0.09, p < .01).
In Hypothesis 1, we postulate that daily transformational leadership relates positively to next-day work engagement through employee strengths use.In Hypothesis 2, we predict that daily transformational leadership relates positively to next-day work engagement through daily employee personal initiative.Significance tests and confidence intervals for the total, direct, and indirect effects are presented in Table 2. Our analysis revealed significant indirect effects from daily transformational leadership to work engagement through both followers' strengths use (β = .016,CI 95%: 0.006-0.026)and personal initiative (β = 0.009, CI 95%: 0.002-0.016).Hence, Hypotheses 1 and 2 were supported.
In Hypothesis 3a, we predict that the positive relationship of daily personal initiative with next-day work engagement is positively moderated by strengths use.In support of this hypothesis, the multilevel analysis revealed that the interaction between personal initiative and strengths use significantly predicts next-day work engagement (β = .07,p < .05).We plotted the interaction effect in Fig. 3.The pattern shows that personal initiative is positively related to next-day work engagement among participants reporting high strengths use, while the corresponding slope for those reporting low strengths use is almost flat.Consistent with the pattern observed, simple slope tests performed at ± 1 SD for both predictor and moderator showed a significant positive slope for participants reporting high strengths use (slope = 0.123, z = 3.494, p < .001)and a nonsignificant slope for participants reporting low strengths use (slope = − 0.001, z = 0.0134, p = .989).Thus Hypothesis 3a was supported as well.
Hypothesis 3b postulated that the indirect relationship of daily transformational leadership with next-day work engagement through employee personal initiative is stronger when employees are high (vs.low) in strengths use.Formally testing the conditional indirect effects revealed a significant indirect effect between daily transformational leadership and work engagement through personal initiative for employees scoring high in strengths use (B = .016,p = .024),while the corresponding indirect effect for those scoring low on strengths use was not significant (B = 0.000, p = .988).Hence, Hypothesis 3b was also supported.
In Hypothesis 4, we predict that daily transformational leadership is positively related to next-day job performance first through daily strengths use and then through next-day work engagement.The lower part of Table 2 shows that the expected sequential mediation from transformational leadership to next-day job performance through strengths use and work engagement was weak but significant (β = .09,CI 95%: 0.002-0.016).Hence, the results support Hypothesis 4. Finally, we predict in Hypothesis 5 that daily transformational leadership positively relates to next-day job performance first through daily personal initiative use and then through next-day work engagement.The results show that this sequential mediation effect was nonsignificant (β = .001,CI 95%: 0.000-0.002).Thus, Hypothesis 5 was not supported.

Discussion
A central goal of transformational leadership is to motivate followers to lead themselves (Avolio & Gibbons, 1988).Transformational leaders challenge followers to think creatively and independently (Bass & Avolio, 1990) and encourage proactive behavior by developing, stimulating, and empowering employees (Den Hartog & Belschak, 2012;Schmitt et al., 2016).The current study demonstrates that when leaders show transformational leadership behaviors, they inspire their followers to use their strengths and be proactive.These behaviors, in turn, seem to foster work engagement and enhance performance.Below, we discuss the main theoretical contributions in more detail.

Theoretical contributions
The present study makes several contributions to the literature.First, our study expands transformational leadership theory by proposing that when leaders are transformational, they can influence important agentic behaviors of their followers-namely, strengths use and personal initiative.These findings speak directly to a central proposition in transformational leadership theory-that leaders inspire followers to lead themselves.Our findings are consistent with Den Hartog and Belschak (2012), who showed that transformational leadership is positively related to personal initiative and prosocial proactive behavior, particularly for employees who have considerable autonomy but also sufficient self-efficacy.Our study expands these findings by showing that (a) transformational leadership translates into employee strengths use and personal initiative; (b) strengths use and personal initiative subsequently predict work engagement (and strengths use also affects job performance); and (c) these effects hold at the day level.Thus, on days when leaders show transformational leadership behaviors, their followers are encouraged to use their strengths and personal initiative.In addition, the findings are in line with Wang et al. (2017), who found that leaders with a transformational leadership style encouraged their followers to look for challenges and resources (i.e., job crafting), partly by increasing followers' adaptability and flexibility.The present results expand Wang et al.'s findings by indicating that when leaders encourage followers to take personal initiative, they foster follower engagement, particularly when followers use their strengths.Leaders who inspire, stimulate, and listen to followers engender vigor, enthusiasm, and absorption in the workplace (i.e., work engagement; see also Amor et al., 2020) and indirectly contribute to their followers' daily job performance.
Second, this study contributes to character strengths theory by showing that leadership can be a crucial predictor of strengths use.Previous research has primarily focused on the possible consequences of strengths use, including self-efficacy and well-being, and, to a lesser extent, performance (Bakker & Van Woerkom, 2018;Miglianico et al., 2020).The present study suggests that transformational leadership may be important for the identification and use of follower strengths.Transformational leaders motivate their followers by determining what their unique qualities and abilities are and encouraging followers to use those strengths.This finding is consistent with transformational leadership theory.Bass (1985) identified a number of developmental behaviors when conceptualizing individualized consideration, including carefully observing staff, encouraging followers to attend courses, providing challenges, monitoring followers' progress, and offering career counseling.Rafferty and Griffin (2006) showed that developmental leadership behaviors are particularly positively associated with role breadth self-efficacy, job satisfaction, and affective commitment to the organization.By showing transformational leadership behaviors, leaders inspire followers to use their strong points when they are confronted with various job demands (Van Woerkom, Bakker, & Nishii, 2016) so that followers can do their work with confidence and engagement (Bakker & Van Woerkom, 2018).
This study also illuminates the role of the leader in proactive behavior theory and shows when personal initiative is most likely to foster work engagement and performance.This is our third contribution to the literature.We proposed that personal initiative would be most effective when employees use their strong points.Personal initiative can take various forms, including seeking feedback, taking charge, using voice, innovating, and seeking challenges (Park, Peterson, & Seligman, 2004;Tims & Bakker, 2010).We argued and found that such initiatives are most likely to be effective on days when individuals use their personal strengths.When employees seek feedback or challenges, they try  to optimize their fit with the job, and such attempts are most likely to be successful when employees use their strong points, such as social intelligence, kindness, curiosity, or perseverance.For example, whereas social intelligence will help individuals proactively garner social resources, perseverance will help to persist toward goals despite obstacles, disappointments, or discouragements (i.e., hindrance demands in JD-R theory).The present study suggests that the use of such strengths helped naval cadets effectively take personal initiative, since the combination of strengths use and proactive behavior fueled work engagement and predicted better job performance.
In the present article, we have argued and shown that encouraging strengths use is important for follower work engagement and performance.However, this does not mean that leaders and followers should completely avoid improving possible weaknesses.Training, coaching, performance feedback, or on the job learning processes are important means to narrow competence gaps.Such human resource practices can repair weaknesses and lead to considerable performance improvements (Van Woerkom, Mostert, et al., 2016).However, on the days employees take personal initiative (e.g., change their tasks, use voice, increase their challenges), they may want to avoid ways of thinking, feeling and behaving that do not come naturally (i.e., weaknesses or deficits).Since organizations as a whole are confronted with changing environmental demands, their employees may not be fully equipped with all the talents and skills needed to deal with these demands.Therefore, organizations and their leaders may want to continuously nurture strengths as well as repair weaknessesthereby promoting excellence and remedying deficits (Linley et al., 2006;Van Woerkom, Mostert, et al., 2016).
A final, more methodological contribution of the present study is that we used a daily diary design and followed naval cadets for no less than 30 days during their voyage from Northern Europe to North America.Although several studies have now used a within-person perspective to study leadership or proactive behavior, the vast majority of studies have used a between-person design to uncover how leadership traits or styles are linked to trait-like proactive behaviors.We changed this perspective and argued that all leaders can make a difference in followers' work behaviors, engagement, and performance when leaders enact transformational leadership behaviors (cf.Daniels, 2006).Moreover, we used a lagged research design to investigate how transformational leadership fosters strengths use and personal initiative on one day only and the degree to which it is indirectly related to next-day job performance through next-day work engagement.With our methodological approach, we also avoided a consistent problem among previous survey research efforts by which the transformational leadership concept was self-reinforcing in nature (Van Knippenberg & Sitkin, 2013).Specifically, whereas previous research often embedded the effect of leadership in the measurement of leadership, we used concrete statements referring to daily leadership behaviors and related these to daily follower behaviors and work engagement.
It is important to note that Bass's (1985) full-range leadership theory distinguishes between transformational leadership and transactional and laissez-faire leadership.Our study was limited to investigating the possible links of transformational leadership with follower work behaviors, engagement, and performance.However, the large meta-analysis by Judge and Piccolo (2004) showed that some forms of transactional leadership-particularly contingent reward-can also predict important criteria.Moreover, the meta-analysis showed that there were several criteria (follower job satisfaction and leader performance, specifically) for which contingent reward leadership had stronger relations than transformational leadership.Additionally, Judge and Piccolo found that transformational leadership was strongly negatively related to laissez-faire leadership.This raises the question of whether other forms of leadership may be equally effective in encouraging strengths use and personal initiative.Future research may be inclined to test the relationships of contingent reward, laissez-faire leadership, and other leadership types (e.g., empowering leadership, servant leadership) with follower work behaviors.

Limitations
The present study makes several contributions but is not without limitations.First, we proposed a mediation model and tried to control the causal ordering of the variables by investigating lagged effects.However, some of the study variables were assessed at the same moment, which makes it impossible to know which variable comes first.For example, it is possible that strengths use and personal initiative shown by followers makes leaders more likely to encourage followers to use these behaviors.Nevertheless, our model was based on transformational leadership theory, which proposes that transformational leaders facilitate followers to lead themselves.Furthermore, although high-quality job performance may function as positive feedback and predict work engagement, job demands-resources theory (Bakker & Demerouti, 2017) proposes that work engagement precedes performance.Second, our sample is very specific-we only investigated naval cadets sailing across the Atlantic Ocean.The specific working conditions on board the ship are rather unique and do not generalize to most other organizations.Nevertheless, our study had high ecological validity, and the psychological processes taking place between leaders and followers in this particular context may not necessarily differ from more A third potential limitation is that the two-level model used in the multilevel analyses did not adjust for possible team-level effects.However, preliminary three-level analyses showed that team membership did not explain a significant proportion of variance beyond the day and person levels and therefore is very unlikely to have threatened the validity of our findings.Fourth, some of the effects were relatively small.This may partly be because we tested lagged effects, where the outcomes were measured one day after the predictors (transformational leadership and follower behaviors) were assessed.Additionally, it is important to realize that each leader was responsible for eight followers.This means that leaders needed to be selective in how much time they spent each day on each follower.Followers were able to report the effects as requested, but eight followers shared one leader.
Fifth, we focused on transformational leadership and its positive links with follower work engagement and performance.However, at times, leadership may also be negative or destructive (for a recent metaanalysis, see Mackey et al., 2021).While destructive leadership was not the focus of the current study, it is important to determine whether daily transformational leadership continues to have positive links with work engagement and performance if leaders sometimes threaten or intimidate their followers.Future studies may test such shifts in leadership behaviors from day to day and their impact on followers' behaviors and work engagement.
A final limitation is that we measured transformational leadership on a short scale and treated the concept as an overall construct.The reason for this was to reduce the number of items and avoid overburdening the participants with lengthy questionnaires.However, the consequence was that we were unable to investigate the relationships of the separate transformational leadership dimensions with follower behaviors, work engagement, and performance.Future diary research may focus on the unique contributions of the separate transformational leadership dimensions-idealized influence, inspirational motivation, intellectual stimulation, and individual consideration.

Practical implications
The present study has several implications for human resource practices aimed at increasing employee work engagement and performance.First, the findings underscore the relevance of transformational leadership as a goal for leadership training.This may be particularly true in work contexts that are dependent on swift, decentralized decisionmaking and initiative by those challenged by dangerous situations that may change unexpectedly, such as those in military and other operational occupations.In such a context, delays in adapting to changed circumstances due to a lack of personal initiative may cause severe consequences.It is evident that here, leadership behaviors that stimulate followers' personal initiative (i.e., transformational leadership) are of high importance.
Second, the finding that work engagement was highest when followers used their strengths while being proactive suggests that organizations that desire more engaged and productive employees could benefit from paying closer attention to employees' character strengths.By helping followers identify their strong points, transformational leaders may be better able to turn their proactive efforts into effective functionalities.Trainers and consultants who want to help leaders engage in transformational leadership behaviors may want to include a module in which leaders learn about strengths theory and learn to identify strengths in themselves and in others (see, for example, Meyers & van Woerkom, 2017).
Finally, the current findings illustrate that most leaders have good and bad days in terms of enacting transformational leadership and, as such, show day-by-day variation in how well they stimulate follower performance.This underscores the importance that leaders be aware of their own daily leadership behaviors.Organizations may use this knowledge by providing regular feedback to leaders about how they lead.Leaders may capitalize on this information by strategically using daily transformational leadership behaviors, such as individual consideration and inspirational motivation-particularly on days when this is most needed (cf.Breevaart & Bakker, 2018).This requires leaders to actively monitor and regulate their own behaviors from day to day.Such an approach will most likely also contribute to the agility of the organization.

Conclusion
This study has shown that transformational leadership is important for follower work engagement and performance because it encourages agentic follower behaviors such as strengths use and personal initiative.When leaders are idealized, show individual consideration, and/or are motivating and intellectually stimulating, they inspire their followers to use their strengths and take personal initiative.This helps followers perform well because they are able to mobilize the energy and enthusiasm to remain focused.As proposed by the full-range leadership model (Bass, 1985), through transformational leadership, leaders truly seem to "transform" followers because followers are stimulated to use their character strengths and lead themselves.We hope that our study will provide a source of inspiration for leadership scholars across the globe to validate and expand the proposed leadership model.In this way, we hope to add insight into how leaders influence follower work behaviors, engagement, and performance.

Hypothesis 4 .
Daily transformational leadership is positively related to next-day job performance first through daily strengths use and then through next-day work engagement.Hypothesis 5. Daily transformational leadership is positively related to next-day job performance first through daily personal initiative and then through next-day work engagement.
Daily strengths use was measured with Van Woerkom et al.'s (2016b) 4-item instrument.Examples are 'Today, I used my talents at work' and 'Today, I have applied my personal qualities in my job' (1 = to a very limited degree; 5 = to a very large degree).Cronbach's α was 0.95 across the 30 days.

Fig. 1 .
Fig. 1.Proposed model of daily transformational leadership and follower performance.
A.B.Bakker et al.

Fig. 3 .
Fig. 3. Interactive effect of daily personal initiative and strengths on daily work engagement.

Table 1
Means, standard deviation, and correlations for all study variables.
*Notes.N = 57 participants and N = 1710 occasions.Correlations below the diagonal are correlations on the within (day).Level and correlations above the diagonal are correlations on the between (person) level.*p < .05,**p < .01.

Table 2
Maximum likelihood parameter estimates, standard errors, and confidence intervals for total, direct and indirect effects in sequential mediation models.