Abstract
Research has suggested that employees who possess a proactive personality have greater job satisfaction. However, contextual factors that may serve as boundary conditions have received insufficient attention in the research. Accordingly, this study proposed psychological safety as a moderator in the positive relationship between proactive personality and job satisfaction. We recruited 207 employees to complete a two-wave panel survey that was conducted over 3 months. When job satisfaction was controlled for at Time 1, this study found that having a proactive personality was positively associated with changes in job satisfaction over time. Furthermore, the relationship between proactive personality and changes in job satisfaction was strengthened when psychological safety was low. The implications and applications are discussed.
JEL classification:
1. Introduction
Proactivity refers to the phenomenon in which individuals exhibit anticipatory actions to take control of and change themselves and/or their life situation (Grant and Ashford, 2008; Parker et al., 2010). Proactivity involves the attributes of being self-initiating, change-oriented, and future-focused, and it leads individuals to actively challenge the status quo to improve themselves or their situation to create a different future for themselves (Parker et al., 2010). Because of the beneficial role of proactivity, previous research has identified a critical disposition that encourages individuals to be proactive, namely, proactive personality (Bindl and Parker, 2011; Crant, 2000). As a fundamental disposition, the proactive personality has been widely investigated and found to contribute to desirable work experiences, such as proactive work behavior (Parker et al., 2006) and job performance (Fuller et al., 2010), career satisfaction (Erdogan and Bauer, 2005), career success (Seibert et al., 1999), and job satisfaction (Li et al., 2010). In this study, we especially focus on the relationship between proactive personality and job satisfaction because it has been regarded as a comprehensive indicator of positive work experiences and encompasses the above-mentioned outcomes (i.e. behavior, performance, and well-being) as well as career success (Judge and Hurst, 2008).
1.1. Conceptual background
Although the positive relationship between proactive personality and job satisfaction has been recognized (Fuller and Marler, 2009; Grant and Ashford, 2008; Parker et al., 2010; Thomas et al., 2010), the use of a cross-sectional design to understand the beneficial role of proactive personality in shaping the development of job satisfaction is currently limited. If so, the investment of resources to cultivate employees’ proactive personality would be valuable to an organization (Tornau and Frese, 2013).
Moreover, the proactivity literature has asserted that proactive personality directs one’s personal life to attain positive outcomes regardless of the constraints of situations (Parker et al., 2010). However, the empirical evidence does not seem to unanimously support this claim. Some studies have reported that proactive employees may be more productive in favorable environments (e.g. Erdogan and Bauer, 2005; Fuller et al., 2010), whereas other studies have indicated that contextual attributes may not exert an effect on proactive employees (e.g. Li et al., 2010). These inconsistent findings suggest the need to delve more deeply into the attributes of the context (Bateman and Crant, 1993). In other words, clarifying the favorable or detrimental conditions for workers with a proactive propensity may be critical to explain when individuals demonstrate proactivity in workplace.
Based on the attachment perspective, proactivity scholars have argued that interpersonal climate and social processes, such as psychological safety, might regulate individuals’ assessment of whether the existing work environment (i.e. work group) is secure for risk-taking (Edmondson, 1999: 354) and proactivity at work (Parker et al., 2010); however, this assumption has rarely been examined. Specifically, because being proactive involves potential risk-taking (e.g. misguided actions; Campbell, 2000), the consequences of one’s engagement are unknown (Wu and Parker, 2014). In this case, employees’ perception of whether the work environment is safe may matter because it establishes a threshold to withstand the serious costs of being proactive (Grant and Ashford, 2008). Nevertheless, we argue that if proactive workers perceive low psychological safety, they would be activated to strive for self-fulfillment, as they always try to make things happen, even against others’ opposition that increasing their job satisfaction eventually (Bateman and Crant, 1993). On the contrary, strong psychological safety might substitute for the influence of proactive personality, which results in a null association between proactive personality and changes in job satisfaction.
1.2. Contributions of the present study
Overall, our study intends to contribute to the literature in several ways. First, we conducted a longitudinal study to examine the assumption in the proactive literature that proactive personality continually shapes employees’ positive work experiences. Second, we investigate a new boundary condition of the proactive personality that is psychological safety. This investigation not only extended our knowledge regarding the interplay between relational factors and proactive disposition in their association with the employee’s job satisfaction over time but also reconciled the seemly opposite perspectives in the proactivity literature. Below, we provide arguments to support our hypotheses.
1.3. Proactive personality and changes in job satisfaction
Job satisfaction refers to an overall evaluation of personal work experiences (Locke, 1976) that represents work and career success (Judge and Hurst, 2008). Job satisfaction is a central consideration in organizational behavior and occupational health (Judge et al., 2002). Thus, the research on proactivity has attempted to identify the possible antecedents of job satisfaction. Among these antecedents, proactive personality is a frequently mentioned construct. An individual who exhibits a proactive personality tends to initiate action to change and to achieve an ideal self or situation (Bateman and Crant, 1993; Crant, 2000).
Theoretically, research has recognized that proactive personality contributes to higher job satisfaction over time through three essential features, namely, that a proactive personality is self-initiated, change-oriented, and future-focused (Grant and Ashford, 2008; Parker et al., 2010). Rather than passively reacting to assigned tasks in a given condition, proactive people develop their own goals (self-initiated; Bindl and Parker, 2011; Parker et al., 2006), anticipate potential problems and opportunities, and demonstrate a personal ability to take control (change-orientated; Parker and Collins, 2010; Parker et al., 2010). Specifically, regarding the goal-attainment process, proactive individuals have a long-term focus that enables them to identify new information, seek feedback for self-growth, and create novel ideas or work strategies to fulfill their aspirations (Bateman and Crant, 1993; Parker and Collins, 2010).
Based on these three features, proactive employees are motivated by their aspirations and are expected to have higher job satisfaction over time because they are not satisfied with their current situation and are inclined to take action to improve it to reach a desired state (Frese et al., 1997). Those with a highly proactive personality try to remove impediments (Erdogan and Bauer, 2005) and achieve their aspirations by engaging in active opportunities and work (Parker and Collins, 2010). Accordingly, proactive employees can create favorable conditions to achieve work success (Li et al., 2010), thereby leading individuals to be more satisfied with their state (Frese et al., 1997). These behaviors become a positive loop that supports their desire to change themselves and their environment, which leads to job satisfaction over time. Empirically, meta-analysis studies consistently found a significant positive association between proactive personality and job satisfaction (Fuller and Marler, 2009; Thomas et al., 2010; Tornau and Frese, 2013). We propose the following hypothesis.
Hypothesis 1 (H1). Employees’ proactive personality at Time 1 is positively associated with their job satisfaction at Time 2 after controlling for their job satisfaction at Time 1.
1.4. Moderating role of psychological safety
Edmondson (1999) has claimed the need of psychological safety for individuals to change. In this study, we further propose that the positive relationship between a proactive personality and changes in job satisfaction will be contingent on psychological safety. The authors consider that psychological safety may be similar to the concept of a secure base, which represents an intimate support–provider relationship to encourage individuals to explore the outside world (Bowlby, 1988). Although the facilitating effect seems to exist, more details are discussed in the sections below concerning proactive employees who perceive psychological safety to be high or low.
In this study, we speculated that psychological safety triggers similar mechanisms as a proactive personality would. That said, psychological safety might substitute for the influence of proactive personality on changes in job satisfaction. Psychological safety represents a coherent, safe climate that supports innovation and the challenging of norms in the workplace (Edmondson, 1999; Ortega et al., 2014). Accordingly, employees who perceive high psychological safety may be prompted to facilitate proactivity and may be more willing to explore at work, regardless of the extent of proactive disposition. Psychological safety “reduces perceived threats, removes barriers to change, and builds a favorable environment which encourages provisional tries and which tolerates failure without retaliation, renunciation, or guilt” (Schein and Bennis, 1965: 45). A sense of high psychological safety enables employees to feel safe at work in order to grow, contribute, and perform effectively there (Edmondson and Lei, 2014; Frazier et al., 2017). As such, employees may be more likely to receive positive feedback from their organization and employer in general (Edmondson, 1999; Hood et al., 2015), which results in higher job satisfaction over time.
However, a proactive personality may matter most when psychological safety is low, according to the proactive literature (Parker and Collins, 2010; Parker et al., 2010). From the theoretical perspective of proactivity, it is expected that employees with a high proactive personality are highly self-starting, change-oriented, and future-focused, and these qualities attempt to improve work processes (change the situation) to enhance effectiveness in the longer term (achieve a different future). However, low psychological safety may offer a unique opportunity to motivate proactive employees. Although perceived low psychological safety may indicate relatively difficult working conditions, a proactive personality would continually drive employees to strive to create change in the environment, even against others’ opposition (Bateman and Crant, 1993). This process of actively making things happen rather than passively seeing things happen under relatively unfavorable working conditions may create intense achievement that contributes to job satisfaction over time. Thus, we propose our second hypothesis:
Hypothesis 2 (H2). The positive relationship between employees’ proactive personality and changes in job satisfaction will be moderated by psychological safety, such that the relationship between a proactive personality and changes in job satisfaction will be stronger when the psychological safety is low.
2. Method
2.1. Procedure and participants
We collected data using a two-wave, time-lagged, panel design. The participants were employees from 12 public fitness centers in Taiwan. Initially, the authors visited 12 human resource managers from each public fitness center, and we explained the purpose of the study, invited potential participants, and procured research approval. In appreciation for their participation, every participant was given NT$200 as a reward. The confidentiality of the respondents was assured. In the first phase, we administered a survey that measured the proactive personality, psychological safety, and job satisfaction (Time 1) of the employees and obtained their demographic information. In the second phase (3 months later), we invited the participants to report their job satisfaction again (Time 2). After the data of waves 1 and 2 were matched, 207 participants within 39 work groups 1 with complete information were retained for a response rate of 60.9%. Of the 207 participants, 107 were male (51.7%), and the mean age was 34.0 (standard deviation (SD) = 11.76).
2.2. Measures
2.2.1. Control variables
The control variables in this study included gender (dummy-coded as female = 1), age (years), job type (dummy-coded as full time = 1), organizational tenure (years), and job satisfaction at Time 1. In particular, we controlled for job satisfaction at Time 1 to examine the variance in job satisfaction.
2.2.2. Proactive personality
The original 17-item Proactive Personality Scale (PPS) was developed by Bateman and Crant (1993). This scale assesses an individual’s relatively stable tendency toward proactivity. Over time, previous studies have used several brief forms of the PPS (with 10, 6, 5, and 4 items; Claes et al., 2005) in which the items with the highest loadings were adopted. In this study, we adopted the 4-item version that has been used in prior research (Lin et al., 2014; Lu, 2017; Parker and Collins, 2010; Parker and Sprigg, 1999; Parker et al., 2006). This 4-item measure has presented adequate reliability in past research. For example, the longitudinal investigation of Lin et al. (2014) reported that the 4-item PPS had satisfactory internal consistency across time (Cronbach’s α of .78 and .85). Cronbach’s α in this study was .83 at Time 1. The response scale ranged from 1 (strongly disagree) to 7 (strongly agree). A sample item was “No matter what the odds, if I believe in something, I will make it happen.” All items are listed in Appendix 1 to this article.
2.2.3. Psychological safety
We assessed psychological safety using the 7-item scale developed by Edmondson (1999). These items evaluate the extent to which employees believe that their team or department is safe for interpersonal risk-taking (Edmondson, 1999). An illustrative item was “Members of this team are able to bring up problems and tough issues.” The response scale ranged from 1 (strongly disagree) to 7 (strongly agree). Cronbach’s α was .82 in the study of Edmondson (1999) and was .89 at Time 1 in this study.
2.2.4. Job satisfaction
Job satisfaction was measured with a 5-item job satisfaction scale. This scale has been used in previous studies (Judge et al., 2000, 2001; Scott and Judge, 2006) to assess employees’ subjective experiences at work. Example items were “I find real enjoyment in my work” and “I consider my job to be rather unpleasant (reverse).” The response scale ranged from 1 (strongly disagree) to 7 (strongly agree). The average internal consistencies of the 5-item measure were .80 or above in the previous studies (see Judge et al., 2001, for a review). In this study, Cronbach’s α was .74 at Time 1 and .72 at Time 2.
3. Results
3.1. Data analysis and aggregation
Because our initial purpose was to investigate whether proactive personality relates to a longitudinal change in job satisfaction, we adopted a residual change analysis (i.e. controlling for the initial score on job satisfaction) to examine the relationship between proactive personality and changes in job satisfaction (Little et al., 2006). Specifically, including the baseline score of the dependent variable as a predictor allowed us to test the longitudinal change in the dependent variable; that is, controlling for the past relationship between the same constructs captures the change from Time 1 to Time 2. Following this procedure, we controlled job satisfaction at Time 1 to examine the relationship between proactive personality and job satisfaction at Time 2.
In testing the hypotheses of the moderation effect, as workers were nested within different work groups, proactive personality and job satisfaction at Time 2 were likely to be influenced by different work groups in terms of their strategic functions for the organization. As such, there might be significant variation among work groups regarding the extent to which members perceive that psychological safety exists in the organization. Therefore, we conducted hierarchical linear modeling (HLM) to test our hypotheses (Bryk and Raudenbush, 1992). To control the group effects in our HLM model, we followed the approach of Bryk and Raudenbush (1992) by leaving the random error in the Level 2 intercepts to be freely estimated. Moreover, we estimated a cross-level moderating model that sets the random error in the Level 1 slopes to be freely evaluated. Finally, we followed Hofmann and Gavin’s (1998) suggestion to group mean center the Level 1 predictor (i.e. proactive personality) when testing our hypotheses.
3.2. Preliminary analysis
We employed confirmatory factor analysis to test the construct validity of the key model variables. The fit indices of the four-factor model (including proactive personality, psychological safety, job satisfaction at Time 1 and job satisfaction at Time 2) were adequate (SB-χ2(183) = 491.97; root mean square error of approximation (RMSEA) = .09 (.08; .10); comparative fit index (CFI) = .82; Tucker–Lewis index (TLI) = .80; standardized root mean square residual (SRMR) = .09) and were better than the three-factor model where the two time points of job satisfaction were aggregated (SB-χ2(186) = 724.90; RMSEA = .12 (.11; .13); CFI = .69; TLI = .65; SRMR = .10) and one-factor model in which the all variables were combined into one factor (SB-χ2(189) = 1224.57; RMSEA = .16 (.16; .17); CFI = .40; TLI = .33; SRMR = .15).
3.3. Descriptive statistics and HLM null models
The means, SDs, correlations, and reliability statistics of the variables included in this study are presented in Table 1. The correlations between proactive personality and job satisfaction were as expected. Proactive personality positively correlated with job satisfaction at Time 1 (r = .13, p < .05) and Time 2 (r = .16, p < .01). Psychological safety positively related to job satisfaction at Time 1 (r = .42, p < .01) and Time 2 (r = .27, p < .01). Moreover, proactive personality had a positive association with psychological safety (r = .18, p < .01). We also conducted a paired-samples t test to examine whether job satisfaction changed from Time 1 (M = 4.72, SD = 1.00) to Time 2 (M = 4.53, SD = 1.02). Result revealed that job satisfaction from Time 1 to Time 2 was significantly different (t = 2.85, p < .05), implying that employees’ job satisfaction was influenced by potential factors. Therefore, we further conducted a series of analysis to test our hypotheses.
Descriptive statistics, reliabilities, and correlations of the variables.
SD: standard deviation.
p < .05; **p < .01.
Prior to hypothesis testing, we followed a suggestion from Hofmann (1997) to conduct HLM. Specifically, we conducted a one-way analysis of variance (ANOVA) to examine whether any significant between-group variance existed in terms of job satisfaction at Time 2. The results of the null model (i.e. no predictors were entered into the equation) showed that there was significant between-group variance (χ2(38) = 59.49, p < .001; ICC(1) = .10) for job satisfaction at Time 2.
3.4. Hypothesis testing
The HLM results are shown in Table 2. Hypothesis 1 proposed that proactive personality was positively related to job satisfaction at Time 2. As shown in Model 2, after controlling for gender, age, job type, organizational tenure, and job satisfaction at Time 1, proactive personality was positively related to job satisfaction at Time 2 (γ = .18, p < .01). Hypothesis 1 received support. With respect to Hypothesis 2, we found that the interaction between proactive personality and psychological safety was negatively associated with job satisfaction at Time 2 (γ = −.12, p < .05; see Model 4 in Table 2). To further explore the form of this cross-level interaction, we probed the interaction by calculating simple slopes for the effect of proactive personality on job satisfaction at Time 2 at specified values of psychological safety using the method and associated utility discussed in Preacher et al. (2006) for cross-level analyses. We assessed the simple slopes at 1 SD above and below the mean for psychological safety. The analysis revealed that proactive personality was positively associated with job satisfaction at Time 2 when psychological safety was low (γ = .23, t = 3.21, p < .01), but this association was not significant when psychological safety was high (γ = .07, t = 1.00, p = .32). Therefore, the results supported Hypothesis 2 (Figure 1).
Results of hierarchical linear modeling.
R2 (Level 1 main effect) = (σ2 of Model 1 − σ2 of Model 2)/σ2 of Model 1.
R2 (Level 2 main effect) = (τ00 of Model 2 − τ00 of Model 3)/τ00 of Model 2.
R2 (Cross-level moderating effect) = (τ11 of Model 4 − τ11 of Model 3)/τ11 of Model 4.
p < .05; **p < .01; ***p < .001.

Interaction plot of proactive personality and psychological safety in predicting changes in job satisfaction at Time 2.
4. Discussion
The purpose of this study was to investigate the relationship between proactive personality and changes in job satisfaction. Our findings demonstrated that proactive employees had higher job satisfaction than their colleagues over a 3-month interval. Moreover, the results revealed that psychological safety moderated the association between proactive personality and changes in job satisfaction. In particular, proactive employees experience greater job satisfaction over time, especially when psychological safety is lower. Overall, our hypotheses were supported and provided several contributions to the literature.
4.1. Proactive personality and changes in job satisfaction
Our study contributes to the literature on proactive personality because in this study, a proactive personality was positively related to the development of job satisfaction. Proactive employees experience higher satisfaction with their job than their less proactive colleagues over time. This finding suggests that a proactive personality leads to a change in people’s thoughts and actions. However, there are two types of change across time, namely, mean-level change and rank-order stability (Caspi et al., 2005). Mean-level change refers to changes in the average level of a sample (i.e. between-level), whereas rank order stability involves changes in an individual’s given score relative to others (within-level).
In fact, a proactive personality may contribute to both types of change. For example, Kim and Wang (2008) found through a time-lagged design that a proactive personality at Time 1 predicted feedback-seeking behaviors at Time 2, which suggests that all variance during the time interval changed equally for all participants. In contrast, Lin et al. (2014) supported our study, demonstrating that the between-person differences predict within-person change (Little et al., 2006; Stenling et al., 2017). Their results indicated that proactive students developed higher academic self-efficacy relative to their less proactive classmates over time, which supports rank order stability. These two types of change suggest that a proactive personality may exert effects on people’s cognitions, emotions, and behaviors through different psychological mechanisms.
4.2. The moderating role of psychological safety
In addition, the authors identified psychological safety as an important boundary condition in the relationship between a proactive personality and changes in job satisfaction, which provides theoretical and practical insights. Our finding suggests that a proactive personality is less related to changes in job satisfaction when psychological safety is high. This result somewhat contradicts part of the literature (e.g. Baba et al., 2009; Fuller et al., 2010; Kim and Wang, 2008). However, some evidence has emerged to indicate that personality may be less powerful because context also provides clear cues that evoke common construal, uniform expectancies, and adequate incentives that constrain the expression of individual differences (Cooper and Withey, 2009; Meyer et al., 2010).
Accordingly, we argue that psychological safety evokes similar mechanisms that a proactive personality evokes, and accordingly, psychological safety can substitute for this dispositional trait. First, high psychological safety involves a shared belief of embracing the potential risks and uncertainties of proactivity (Edmondson, 1999; Ortega et al., 2014). This shared belief implies that individuals are also encouraged to challenge the status quo and situational constraints in such a context. Second, psychological safety represents interpersonal trust (Detert and Burris, 2007) and respect (Nembhard and Edmondson, 2006), and immersion in this environment enables employees to comfortably be themselves (Edmondson, 1999), which creates favorable social relationships (Gong et al., 2012). In these conditions, individuals are supported to take the initiative, such as questioning current practices, seeking feedback, engaging in quality improvements, and developing more innovative solutions (Nembhard and Edmondson, 2006).
As a consequence, a proactive personality is less related to changes in job satisfaction when psychological safety is high because of a substitution-type effect. Supporting our argument, Li et al. (2010) reported that a high procedural justice climate allowed individuals to act proactively, and it displaced the influence of a proactive personality on positive work experiences. Although our study was consistent with this part of the literature, further research is needed to clarify the effect of a highly intense situation on personality.
Moreover, we found that a proactive personality was most effective under an unfavorable context (i.e. low psychological safety). Our finding corresponded to an assumption of personality-based proactivity that suggests that people with a high proactive personality are more likely not to be hindered by situational constraints and more likely to anticipate to create changes and achievements (Bateman and Crant, 1993). That is, to actively overcome difficulties at work continually in a less favorable work environment may cause greater achievement and joy, which contribute to the development of job satisfaction. However, several studies have indicated an opposite pattern. For example, proactive employees perform less organizational citizenship behaviors when they are in an unfavorable work environment, such as a perceived lower justice climate (Li et al., 2010). These inconsistent results may originate from the different attributes of moderators and outcomes; however, more research is warranted to support our speculation.
4.3. Implications, limitations, and conclusion
In addition to the theoretical contributions, our results may have important managerial implications. First, the significant association between a proactive personality and changes in job satisfaction indicates that the recruitment of employees with highly proactive dispositions should be one of the top priorities for organizations. This strategy is especially important because proactive employees are more likely to increase their job satisfaction over time even when they face a less favorable work environment. Second, the substitution-type effect of psychological safety suggests that both the person and the work environment are crucial for an organization. The current results indicate that the lowest job satisfaction occurred when the employees scored low in both proactive personality and psychological safety. Based on the substitution-type effect, therefore, one way to increase employees’ job satisfaction may be to design suitable interventions to promote employee proactivity. In this regard, employees may benefit from the substitution-type effect or they may even increase their job satisfaction when they face adversity.
Several limitations of this study need to be addressed. First, the self-reported data might inflate the relationship among our research variables because of common method variance. Future research should address this issue using objective measurements or field experiments to extend our work. Second, we did not investigate the issue of time in this study. We adopted a time-lagged design with a 3-month interval only to assess changes in job satisfaction. Because there is no specific guidance on the probability of when changes in the variables arise, future studies should explore the issue of time regarding optimal time-lagged intervals, which would be helpful to proximally capture the stability and changes of the constructs. Third, this study adopted a two-wave repeated observation to assess the change in job satisfaction, which assumes that the change in constructs from Time 1 to Time 2 is by default linear. Nevertheless, because some organizational phenomena may change in a nonlinear way (Vancouver et al., 2010), research recommends the use of three or more repeated measurements in capturing and testing both linear and nonlinear forms of change (Ployhart and Vandenberg, 2010). Future research should consider this issue in more detail to explore the effect of proactive personality on the dynamic changes in job satisfaction.
Given the critical role of proactivity in contemporary management, this study found that a proactive personality is associated with changes in job satisfaction and that psychological safety acts as a boundary condition that contributes to the theories and applications of proactivity. These findings correspond to the theoretical aspect of proactivity, highlighting how employees with higher proactive personality, even in an unsupportive environment, shape their positive work experiences over time. In addition, our results suggest that high psychological safety in the workplace can substitute for the effect of proactive personality on changes in job satisfaction, providing insights and an impetus for future research.
Footnotes
Appendix
List of research items.
| Variables/items |
|---|
| Proactive personality |
| I am excellent at identifying opportunities. |
| No matter what the odds, if I believe in something, I will make it happen. |
| I love being a champion for my ideas, even against others’ opposition. |
| If I believe in an idea, no obstacle will prevent me from making it happen. |
| Psychological safety |
| If you make a mistake on this team, it is often held against you. (Reverse item) |
| Members of this team are able to bring up problems and tough issues. |
| People on this team sometimes reject others for being different. (Reverse item) |
| It is safe to take a risk on this team. |
| It is difficult to ask other members of this team for help. (Reverse item) |
| No one on this team would deliberately act in a way that undermines my efforts. |
| Working with members of this team, my unique skills and talents are valued and utilized. |
| Job satisfaction |
| I feel fairly satisfied with my present job. |
| Each day at work seems like it will never end. (Reverse item) |
| I find real enjoyment in my work. |
| Most days I am enthusiastic about my work. |
| I consider my job to be rather unpleasant. (Reverse item) |
Final transcript accepted 29 October 2018 by Peter Jordan (AE organizational behavior).
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was supported by Ministry of Science and Technology (102-2410-H-003-133-MY2, 104-2410-H-003-040, MOST 106-2410-H-143-014 & MOST 107-2628-H-029-002-MY2), Taiwan.
