A M ODEL OF A NTECEDENTS S TRENGTHENING O RGANIZATIONAL OMMITMENT

Primarily due to the importance of organizational commitment for both employees and employers, over the last few decades, the model of antecedents has continued to attract researchers. Hence, in this paper, the authors aim to build a model of antecedents to strengthen organizational commitment. In this study, the authors reviewed six main concepts and then applied the quantitative methods to research. The findings show that the three most prominent factors positively affecting organizational commitment are intrinsic motivation, extrinsic motivation, and organizational identification. This model will facilitate leaders to make plans of action to design suitable and efficient policies for motivating employees to increase their job performance and be more committed to their organization.


I. INTRODUCTION
The concept of organizational commitment has received increased attention from scholars and practitioners over the world. They have researched and conducted several social experiments to increase employee commitment to organizations [28], [36]. Employees are considered as a part of an organization's assets; therefore, they play a central role for several reasons. As confirmed in [3] and [6], employees feel the close relationship between the goals and values of the organization and organizational commitment. Previous research also reveals that highly-committed employees perform much better than less committed ones [30], [36]. According to [39], organizational commitment consists of three main categories. The first type, affective commitment, relates mainly to identification with and involvement in emotional attachment. The second one is continuance commitment, which is based on the leaving organizational costs. Normative commitment is the third type, which is known as a sense of obligation to the organization [39]. In fact, organizational commitment has been defined and conducted in a variety of research perspectives and methods.
To contribute more empirical results, the purpose of this paper aims to propose a model of antecedents strengthening organizational commitment in the context of Vietnamese organizations in order to help leaders create plans of action or design suitable and efficient policies for motivating employees to increase their job performance and be more committed to their organization. In this study, the results were collected using a survey of 249 fulltime Vietnamese employees working in about 34 Vietnamese organizations from a variety of sectors, such as tax, banking, health service, airlines, education, and business. This paper reviews six main concepts: organizational commitment, intrinsic motivation, extrinsic motivation, employee voice, organizational identification, and perceived organizational support. A Five-point Likert scale was used to measure the collected data. Finally, quantitative research was obtained using EFA, CFA analysis, and structural equation modeling.

II. RESEARCH AIM
This study aims to build upon the model of antecedents that strengthen organizational commitment. The authors investigate what factors significantly affect organizational commitment.

III. LITERATURE REVIEW A. Organizational Commitment
Previously, there was an ambiguity in the concepts of organizational commitment and organizational identification. In recent years, these terms were empirically tested and discussed in [16]. The authors strongly concluded that, whereas organizational identification is selfreferential or self-definitional, commitment is not, and that, while identification is related to perceived similarity and shared fate with the organization, commitment is formed by exchange-based factors known as the relationship between the individual and the organization [16]. Employees feel more attachment to organizational goals and values than toward organizational commitment [3], [6]. As reviewed in [30], the concept of organizational commitment is defined by two main perspectives: behaviors and attitude and can be defined as the relation between an individual's identification and involvement with the organization people work for. Moreover, organizational commitment can be symbolized by at least three elements: "1) a strong belief in arid acceptance of the organization's goals and values; 2) a willingness to exert considerable effort on behalf of the organization; and 3) a strong desire to maintain membership in the organization" [30], [36] and is a process of identification [33]. According to [39], organizational commitment originates from three distinct categories. The first type, affective commitment, relates mainly to identification with and involvement in emotional attachment. The second category is continuance commitment, which is based on the leaving organizational costs. Normative commitment is the third type, known as a sense of obligation to the organization [39].

B. Organizational Identification
Organizational identification is quite different from organizational commitment since it is selfdefinitional or self-referential [16]. The first term that needs to be explained is identification, which is the role's defining essence, which is defined by an individual [2]. As found in [16], organizational identification refers to the individuals' definition of him or herself and is defined as the perception of oneness or belongingness with an organization which he or she is tightly involved in and shares in its successes and failures [27].
To some extent, the concept of identification is related to the three dimensions: oneness, loyalty and shared characteristics. While oneness is the share of common goals with others in an organization, loyalty is shown in terms of the attitudes and behaviors protecting the organization. Shared characteristics are what individuals and others in the organization have in common [25]. In other words, organizational identification is the part of more general definition as "identification with a psychological group which is perceptual rather than affective [1], [27] and it stays when an individual feels proud of being a part of a group and highly appreciates the group's values and achievements without gaining them as his or her possession [5]. Importantly, organizational identification has been criticized to help strengthen a sense of meaning, belonging, and control at the workplace [22]. The fundamental difference between identification and commitment originated from the relationship between individual and organization is that, whereas identification relates to psychological oneness, commitment shows a bond between separate psychological entities [9], [21]. Therefore, in this study, the authors posit that: H1: Organizational identification will positively affect Organizational commitment.
Besides this, motivation also plays an essential role in forming employees' commitment to an organization.

C. Internal and External Motivation
Several researchers have conducted previous studies on motivation and its relationship to organizational commitment [28]. The term motivation is commonly defined as a sense of achievement, recognition for high performance, responsibility, and individual development. It is a psychological process of exchange between individuals and their environments [18], [24]. The two main drivers of motivation are intrinsic and extrinsic [14], [23], [28]. Whereas the former relates to the state of interest and enjoyment, the latter refers to performing a task for instrumental reasons [14], [19]. In other words, while intrinsic motivation is linked to work engagement, positive outcomes, and productivity, extrinsic motivation is built by visible incentives [23]. From another perspective known as selfdetermination theory, as it was revealed in [15], a multidimensional definition of motivation consists of two primary forms: autonomous and controlled. The author prefers the term autonomous because while autonomous motivation is about an individual's optimal functioning, such as well-being and performance, controlled motivation is less beneficial [15].
However, above all, most researchers believe that building effective employee engagement and loyalty does not necessarily relate to money and recognition. Those who have a sense of achievement or job importance are likely to feel more commitment to an organization. That's why most authors confirm that intrinsic drivers dominate extrinsic rewards [18], [23], [28], [38]. This leads to the following hypotheses: H2: Intrinsic motivation will positively affect organizational commitment.
H3: Extrinsic motivation will positively affect organizational commitment.
Motivation cannot exist without receiving support from the organization. Perceived organizational support is viewed as the source of stronger organizational commitment.

D. Perceived Organizational Support
Perceived organizational support (POS) is considered as the antecedent increasing employee's attachment to the organization [11], [34]. It results from organization's treatment to an employee in a wide variety of situations such as illnesses, mistakes, performance [11]. Moreover, POS is considered as employees' perceptions of the organization's commitment which are relied on how the organization recognizes their contributions and supports their well-being [20], [35]. From the same perspective, POS relates to meeting employees' socioemotional needs and the readiness the organization does to appreciate increased work endeavor [12]. This term becomes more interesting for recent studies because it positively affects job satisfaction and organizational commitment [17]. POS will be stronger in case the organization assures to make an employee's job effective and decrease stressful situations [35]. The prominent beneficial influence of POS is that it creates among employees a feeling of obligation to repay the positive treatment they received from their organization [4], [10]. Thus: H4: Perceived organizational support will positively affect Organizational commitment.
Moreover, in order to partly contribute to the organizational outcome, employee voice also plays an important role.

E. Employee Voice
In organizational science, the term 'voice' has been defined in various ways. Voice relates to employees' ability to affect the outcome of organizational decisions by giving them the chance to raise their ideas [13]. Traditionally, it has been defined mostly as criticism of one's work organization, but, recently, voice has been defined as the way of offering improvements and discussing problems in the workplace [7]. In terms of employee voice, it serves several purposes, such as rectifying a problem with management, offering a countervailing source of control to management, contributing to improve quality and outcomes, or suggesting long-term viability for organization [37].
In addition, based on Dyne's study, voice consists of two elements: employees' complaints or grievances at work to management and employees' participation in decision-making processes of the organization, and it is divided into two types: mandated voice and voluntary voice [26]. Similarly, voluntary voice considered as upward voice is preferred by communicating suggestions, information or strategies to management [8], [29]. Levels of employee engagement are either directly or indirectly influenced by employee perceptions of voice behavior targeted at increasing job performance [31]. As a result, the authors propose: H5: Employee voice will positively affect organizational commitment.

IV. RESEARCH METHODS
The data for research is based on a survey of 249 Vietnamese employees who work at 34 Vietnamese organizations from a variety of sectors such as tax, banking, health, airlines, education and business. All the correspondents are subordinates with various titles from middle managers to staff. The questionnaire contained six constructsorganizational commitment, intrinsic motivation, extrinsic motivation, employee voice, organizational identification, and perceived organizational supportand was distributed as hard copies that required handwritten responses. A five-point Likert scale is used to measure those factors with 32 items: totally disagree, disagree, neutral, agree, and totally agree.
A total of 280 handouts of the questionnaire were delivered within six months in Ho Chi Minh City and other neighboring provinces in southern Vietnam. However, only 249 handouts were returned and valid. Quantitative research is conducted by non-probability sampling and obtained by using EFA, CFA analysis, and Structural Equation Modeling.

V. RESULTS
To ensure the items in the questionnaire are valid and reliable, the questionnaire is surveyed by 249 participants. The descriptive statistics result shows that it ranges with means from 3.41 to. 4.0 and its standard deviations fluctuate from 0.756 to 0.976. Moreover, Cronbach's Alpha ratio is 0.966 (>0.8) with 32 items (see Table 1). EFA factor analysis is the next step. It is analyzed in two phases. Phase one is for independent variables, and phase two is for the dependent one.
In the first phase, five independent variablesintrinsic motivation, extrinsic motivation, employee voice, organizational identification, and perceived organizational supportare included in EFA factor analysis with the principal components method and rotation Varimax. Specifically, KMO equals 0.931 (≥0.5) and sig.001 (≤0.05); therefore, Bartlett's Test is statistically significant (see Table 2).  Table 3). In the second phase, the dependent variable "organizational Commitment" is evaluated by EFA analysis. The result is that the evaluation of Cronbach's Alpha for dependent variable "Organizational Commitment" is .916 which is accepted. Furthermore, KMO equals to 0.931 (≥0.5) and sig.001 (≤0.05) that also mean the Bartlett's Test is statistically significant and all factor loadings are more than 0.505 (see Table 4). .000 Figure 1 shows the results of CFA concepts of the research model. P=.000; CFI = .884; TLI = .870; GFI = .781; RMSEA = .084.  The results of CFA factor analysis of the research model are shown in Figure 1. They are presented as follow: P=.000; CFI = .884; TLI = .870; GFI = .781; RMSEA = .084. According to the conditions with P < 0.05; CFI, TLI≥ 0.8; GFI is approximately 0.781 and RMSEA is approximately 0.08, they all meet the requirements. Considering the above conditions, the model is consistent with the market data.

CFA Factor Analysis
Based on the results in Table 5, the parameters (standardized) are statistically significant (p<0.05). However, three factors IM, EM and IO have significant effects on Organizational commitment with P-value < 0.05, while EV with weight of -.034 and P-value 0.635 does not.
According to the regression weight between factors shown, while intrinsic motivation positively affects organizational commitment with weight of .364, extrinsic motivation positively affects organizational commitment with weight of .138. Specifically, when intrinsic motivation goes up by one standard deviation, organizational commitment goes up by 0.364 standard deviations, and when extrinsic motivation goes up by one standard deviations, organizational commitment goes up by 0.138 standard deviations. Similarly, with a weight of 0.649, organizational identification has a positive effect on organizational commitment. Clearly, whenever organizational identification goes up by one standard deviation, organizational commitment goes up by 0.649 standard deviations (see Table 5).

VI. DISCUSSION
Empirical data suggests that the three antecedents mainly affecting organizational commitment are intrinsic motivation, extrinsic motivation, and organizational identification. However, employee voice does not have any affect. This may be explained by the fact that whereas employee voice is mentioned in the organizational commitment literature as the outcome of organizational decision, it is insignificant in statistics-if the voice is mandated and not voluntary, in the long run, it will diminish employees' working enthusiasm and contribution, and decrease job performance [32]. However, based on the three main antecedents that influence organizational commitment, it is clear that motivation plays an important role in encouraging employees to work harder to produce a higher performance, with a sense of achievement, and take more responsibility in their work [18], [25]. Both intrinsic and extrinsic motivation really work well. Even though they have their own individual beneficial values, they are both linked to positive outcomes, higher productivity, and even more organizational commitment. Employees tend to engage in their work and their organization [14], [19], [23]. Evidently, when employees feel engaged, they naturally have the perception of identification. In other words, when they have shared loyalty and characteristics with their organization, they also share in its success or failure as well [25], [27].
Furthermore, they feel proud to be part of the organization and highly recommend to others the organization's values and achievements [5]. Above all, organizational identification is crucial in helping to increase a sense of meaning, belonging, and control at work [22].

VII. CONCLUSIONS AND SUGGESTIONS FOR PRACTICAL USE A. Conclusions
In recent years, there has been special interest in the concept of organizational commitment as it brings several beneficial results to organizations. The term organizational commitment has been variably defined, measured, and researched. However, it has not yet been researched fully in the Vietnamese context. Surveys of 34 organizations-from a variety of sectors such as tax, banking, health service, airlines, education and business-have found that, empirically, there are three main antecedents that positively affect organizational commitment: intrinsic motivation, extrinsic motivation, and organizational identification.

B. Suggestions for Practical Use
The model of antecedents strengthening organizational commitment will help leaders make plans of action, as well as design suitable and efficient policies to motivate employees, in order to increase their job performance and commitment to their organization.

C. Implications
According to the literature on organizational commitment, as well as those previously mentioned, there are three more factors that also have a huge impact. Therefore, for future research-and in order to facilitate higher engagement between employees and their job and organization-these additional factors, and not just the ones mentioned in this paper, should also be investigated.