The Effect of Motive Fulfilment as a Meditating Variable between Perceived Organisational Support and Volunteers’ Affective Commitment in Non-Profit Organisations

In this paper, the influence of organisational factors and the role of individual factors on affective commitment is examined, particularly whether volunteers’ motive fulfilment mediates the influence of perceived organisational support on volunteers’ affective commitment. A cross-sectional survey was used to collect data from 213 volunteers from five non-profit organisations in Queensland, Australia. Perceived organisational support is found to have a significant relationship with volunteers’ affective commitment. Furthermore, motive fulfilment has a significant effect on the impact of perceived organisational support (POS) on the outcome. The results of the study provide new knowledge about the importance of motive fulfilment as a tool for improving volunteers’ positive experiences of an organisation and explain how motive fulfilment promotes increased affective commitment. suggests These results show that supporting the in and improvement increases volunteers’ perceptions of organisational


Introduction
Community non-profit organisations NPOs play an effective role in improving the lives of disadvantaged communities in areas of employment in Australia (Michael 2019), and they heavily depend on the prosocial attitudes of volunteers. This means that NPOs rely on volunteers' continuous commitment to achieve their goals (Alfes et al., 2017;Einolf and Yung, 2018). Hence, having committed volunteers is central to the effectiveness of NPOs in the areas of service delivery, reduced overhead expenses, and other outcomes. Despite these benefits, volunteer commitment and continuity are a huge challenge for community NPOs (Bidee et al., 2013;Vecina et al., 2010). While previous studies have focused on organisational outcomes such as volunteer satisfaction (Nencini et al. 2016) and service tenure (Boezeman and Ellemers 2008), there is a lack of empirical findings and in-depth investigation about other factors affecting the affective commitment of volunteers.
Several studies (see Usadolo, 2016) on paid employees have identified different organisational and individual factors as predictors of affective commitment. The most predominant organisational factor is a supportive organisational climate (Brunetto et al., 2018;Knapp et al., 2017). According to various authors' arguments, the amount of support an organisation provides, or the perceived organisational support (POS) to its employees, is a key predictor of affective commitment. This is based on the premise of Social Exchange Theory (SET) which postulates that employees' perceptions of support from the organisation through its policies and practices increases their belief that the organisation cares about their well-being and values their efforts, which in turn, leads to increased emotional attachment and reduced turnover behaviour. The fact that POS influences several workplace outcomes is not the issue in the literature. The contention, however, is that the literature has not dealt with the likelihood that there might be an intervening variable between POS and several workplace outcomes, especially the motive fulfilment and commitment of volunteers. Hence, in this study, the indirect effect of POS on affective commitment through the fulfilment of volunteers' personal needs will be investigated because of its importance in determining volunteers' affective commitment.
In the current study, whether POS would have the same effect on the motive fulfilment and affective commitment of volunteers as that of paid employees will be examined because organisational support provided to paid employees is different to that of volunteers in NPOs. In this respect, Lee et al. (2014) assert that NPOs are characterised by service commitment; hence, organisational support may not be as important as personal values and the needs that influence workers' motives to work for NPOs. Personal values influence volunteers' desires to commit to volunteering services without monetary rewards, and volunteers are thus drawn to NPOs that have values that are congruent with theirs, but this is usually not the case for paid employees. POS, therefore, will apply to volunteers and paid employees differently because volunteers do not receive monetary rewards for their work like the paid employees do (Usadolo, 2016), and NPOS, as opposed to for-profit organisations, do not have formal rewards and management structures to influence volunteers' behaviours (Alfes et al., 2017). In this regard, Usadolo (2016) argues that NPOs must provide support to volunteers that aligns with their motivation for volunteering. In the same vein, paid employees are part and parcel of their organisation's hierarchy with the policies and procedures to which they are contractually obliged to adhere to, but "volunteers benefit from greater independence in how their work is carried out" (Alfes et al., 2017:63), and this also applies or influences the nature of the social exchange relationships they have with their organisations.
In this study, SET is used as a theoretical framework to explore the impact of POS on volunteers' affective commitment and the intervening effects of motive fulfilment. The contributions of this paper to the existing literature are twofold. First, while there are studies examining the impact of POS on paid employees, there is far less research examining how POS impacts volunteers' affective commitment and motive fulfilment. Hence, the study generalises the impact of POS across different work sectors and, in turn, provides a deeper understanding to those who manage volunteers in community NPOs. Second, this study provides further evidence about how POS as a SET construct affects workplace outcomes by also examining its indirect effect on affective commitment through motive fulfilment. This type of analysis will add to explanations about the contributions and distinctive roles of each of the motives, especially as they relate to volunteers in community NPOs. The model below describes the interactions between these variables. SET is defined as the "voluntary actions of individuals that are motivated by the returns they are expected to bring and typically do in fact bring from others" (Blau, 1964:91). It is an exchange relationship based on the norm of reciprocity that develops mutual trust and commitment (Cropanzano and Mitchell, 2005) between individuals. The exchange can be in the form of favours, assistance, money, access to resources, and activities that enhance self-esteem and respect (Blau, 1964;Cropanzano and Mitchell, 2005). SET is particularly important as an analytic lens in this study given its proposition that, "the more valuable to a person is the result of his action, the more likely he is to perform the action" (Homans, 1961:55). SET is concerned with the degree to which a person finds a specific reward useful when compared to other available rewards (Homans, 1974). In both paid and volunteer organisations, employees and volunteers will see the positive outcomes that result from their actions as rewards and negative outcomes as a sign of inequitable exchanges. This means that the usefulness or benefits of rewards to the recipient are important in terms of obtaining the desired action from the recipient, and these rewards can be attained through POS.
POS is used to explain workplace relationships between organisations and their employees. It signifies the positive support organisations give their employees to meet their day-to-day work objectives and their psychosocial needs. From the literature that focuses on paid employees, POS theorists Rhoades and Eisenberger (2002) posit that employees' socio-emotional needs such as emotional support, affiliation, esteem, and approval (which are some of the essential elements of motive fulfilment) are best met through the support provided by the organisation. This means that POS is based on a relational contract (Farmer and Fedor, 1999;Knapp et al., 2017) that serves as a means by which organisations provide resources that meet employees' needs that are not met by financial rewards. Thus, it is expected that POS will serve as a relational currency in return for volunteers' contributions, which will motivate volunteers to reciprocate the fair treatment they receive from the organisation.
The fact that POS is based on relational rewards makes it an important factor for NPOs that are already experiencing financial difficulties because of the perception that support from the organisation in the form of recognition, autonomy, fair treatment, and job enrichment do not cost money to implement. Such discretionary aids are perceived as an expression of an organisation's positive appreciation of individuals' contributions (Eisenberger et al., 1990) and results in increasing volunteers' feelings of being valued and cared for (Farmer and Fedor, 1999). In paid employees' contexts, research has shown the importance of high-quality POS on a paid employee's wellbeing (Brunetto et al., 2012), retention (Cohen, 2006), commitment , and supervisor-subordinate relationships (Wayne et al., 1997). However, despite the documented findings of the effects of POS on paid employees' attitudes and behaviours, comparable research on the influence of POS on volunteer workplace outcomes is limited. Hence, this study is necessary because it will help to elucidate the effect of POS on volunteers' positive workplace behaviours (affective commitment) that benefit NPOs.

Affective Commitment
Affective commitment is defined as the degree to which an individual is emotionally attached to, identified with, and believes in the organisation's goals (Allen and Meyer, 1990). Affective commitment is the most important type of commitment among volunteers (van Vuuren et al., 2008) because volunteers do not have any financial obligations or contracts with the organisation. Affective commitment is a desirable attitude that every organisation seeks to encourage because individuals who are affectively committed to their organisations usually have a strong affiliation with and are loyal to their organisation (Rhoades et al., 2001). This means that volunteers in community NPOs in Australia who are emotionally attached to their organisations will be more engaged in organisational activities. For example, both Penner and Finkelstein (1998) and Grube and Piliavin (2000) found a significant positive association between organisational commitment and the number of hours per week volunteers reported working in organisations. Non-commitment has been associated with stress, low levels of morale, and withdrawal behaviours (Cooper-Hakim and Viswesvaran, 2005). In addition, Mowday et al. (1982) argue that a non-committed individual may not present a good image of the organisation to the community.
Affective commitment has been found to be one of the reciprocal behavioural states used by employees as repayment to an organisation when they perceive that they are receiving the necessary support from the organisation. Using the notion of the norm of reciprocity, when an organisation relates to an employee positively with respect to access to resources and autonomy, the employee is bound to reciprocate by working hard to improve organisational effectiveness (Brunetto et al., 2013).
Over time, this could develop into emotional ties and a sense of unity with the organisation (Addae et al., 2006). A felt obligation to care about the organisation's welfare and emotional attachment to help the organisation reach its objectives were found in a study of Dutch volunteers who believed they were receiving the necessary support from the organisation they volunteered for (Boezeman and Ellemer, 2007). Based on these findings, the following is hypothesised: Hypothesis 1 (H1): Volunteers perceive that organisational support will be positively related to their affective commitment.

Motive Fulfilment
Motive fulfilment, as used in this study, is built around the view that when reasons (motives) for volunteering are met it results in one or more favourable workplace outcomes. Motive fulfilment is different from motive. Motive, in terms of the functional approach used by Clary et al. (1998), explains the function or reason volunteers have decided to give their time for unpaid activities in an organisation. Hence, it is only when the reason (motive) is being achieved that the volunteer would deem it appropriate to reciprocate. In other words, motive fulfilment, specifically in the context of volunteerism, refers to a state where the volunteers feel their reasons for volunteering have been met. Such reasons could be, according to Clary et al. (1998), to express important values (altruism or values), to obtain better understanding (understanding), to enhance self-esteem (self-esteem), to increase social networks (social), to improve career prospects and opportunities (career), and to reduce self-guilt (protection). Motive fulfilment consists of the six elements stated above in two categories, which are values (altruism) and egoistic motives (understanding, enhancement, social, career, and protective).

Motive Fulfilment as a Mediator
The drive to volunteer is usually perceived as one, or a combination of several, motives (Finkelstein, 2008) and it is assumed that volunteers will be motivated to perform if they are given activities or support that will lead to the fulfilment of their personal motives. According to Penner (2002), volunteers' perceptions about how they are treated in the organisation and the organisation's management practices impact on volunteers' volunteering behaviours. Thus, organisations' policies and processes and the nature of their relationships are all factors that may determine whether volunteers feel their motives are being fulfilled. In this light, Brudney (1999) and Wilson (2000) state that volunteering takes place not only on account of motivation but also because of organisational support. Dwiggins-Beeler et al. (2011) andPenner (2002) also argue that organisational variables (such as POS) or dispositional variables (such as motive fulfilment) may not fully describe volunteers' workplace outcomes alone. Consequently, Penner suggests that dispositional variables can be mediators in the relationship between organisational variables and workplace outcomes. Therefore, POS is expected to be an antecedent of motive fulfilment.
Research about the impact of POS on affective commitment has been based mainly on paid employees' general beliefs about organisations valuing them and caring about their wellbeing. The pre-conditional aspect of POS, regarding its fulfilment of the individual's important socio-emotional needs before influencing these outcomes, have received less focus (Lee and Peccei, 2007) for both the paid and volunteer workforce. Hence, the intention of this study is to fill an aspect of this gap by examining the role of motive fulfilment, which has been identified as a need that is important to volunteers and which, if met, is likely to result in volunteers' affective commitment. Based on this, it is expected that the impact of POS on affective commitment will be mediated by the fulfilment of socio-emotional needs, which in this case are volunteers' motives. To test this, the following hypothesis is formulated: Hypothesis 3 (H3): Volunteers' motive fulfilment (altruism, enhancement, understanding, career, social, and protective motives) will mediate the relationship between POS and affective commitment.
Together the hypotheses provide a way forward for informing the research design, as illustrated in Figure 1.

Procedures
This study employed a self-administered survey (cross-sectional research design) to collect data from participants in five community NPOs in Queensland, Australia. Prominent among the community services these NPOs render are the settlement of refugees, advocacy for refugees, community development and engagement with communities, reskilling and employment services, and the sourcing and delivery of clothes to the needy. Two of the NPOs are involved in community respite for people with disabilities as well as advocacy and transport services for people with disabilities. Volunteers who volunteered at least twice a week and had been volunteering for a year or more in these organisations were selected as the sample frame for this study. This was an ideal sample frame as relationships between volunteers and organisations evolved over time. Only 680 volunteers met the criteria, hence, a purposive non-probability sampling was the ideal method to use in this study; such a sample best represents the population. This involved the use of all the volunteers from the five organisations who met the specifications. According to Neuman (2014), an ideal sample should be representative of the population. It should have the features of the population for the findings to be generalisable. Based on this, the desired sample size for this research was 680 volunteers.
Before the distribution of questionnaires, meetings were held with different volunteer coordinators in the NPOs to explain the research project and then permission was sought for data collection. Six hundred and eighty (680) questionnaires were distributed after explaining to the volunteers the importance and aims of the research project during these meetings. Both the volunteer coordinators and volunteers were assured that the information collected would be kept confidential and findings would be reported anonymously. In the end, a total of 218 questionnaires were returned, but only 213 questionnaires were used as five of the questionnaires were incomplete. Most questionnaires were handed out and collected by the researchers after these meetings. Those who were not able to complete their questionnaires at the meetings were given the option to either bring them to the next meeting or send them by post using the stamped, self-addressed envelopes provided. Postage-paid envelopes were given to the participants to return the surveys and still retain their anonymity. In addition, some questionnaires were left with the volunteer coordinators to distribute to those volunteers who were absent. After the data collection, all the data collected were analysed with SPSS Package 23. Descriptive statistics such as means, frequency distributions, and percentages were used to analyse the demographic data.

Measures
POS was measured with the shorter version of the questionnaire developed by Eisenberger et al. (1990). The shorter version is a unidimensional scale comprising of eight questions. This instrument was used because several studies have shown that the shorter version had high internal reliability (see Bang, 2007;Eisenberger et al., 2002;Wayne et al., 1997). All questions were measured using a six-point Likert-type scale in which responses ranged from Strongly Disagree (1) to Strongly Agree (6). An example of a question is: "The organisation cares about my general satisfaction at work." A Cronbach's alpha of .85 was obtained. Clary et al.'s (1998) Volunteer Functions Inventory (VFI) was used to measure the motive fulfilment of volunteers. A total of 12 items were used, and all questions were measured with a six-point Likerttype scale ranging from Strongly Disagree (1) to Strongly Agree (6). An example of a self-value fulfilment question is, "By volunteering at this organisation, I am doing something for a cause I believe in." The Cronbach's alpha for motive fulfilment variables are as follows: self-value (.84), understanding (.82), enhancement (.89), social (.83), protective (.87), and career (.86). Affective commitment was assessed with Allen and Meyer's (1990) measure of employees' emotional attachment to the organisation. All questions were measured on a six-point Likert-type scale with responses ranging from Strongly Disagree (1) to Strongly Agree (6). One of the questions was, "I enjoy discussing my organisation with outside people," the Cronbach's alpha for this question is .93. The demographic variables such as gender, age, number of hours volunteered, and years of volunteering were measured with single-item questions.

Demographic Analysis
The percentage of the total data collected from the five community NPOs as compared to the number of questionnaires given out was 32.7 per cent. Like the report of National Survey of Volunteering Issue (2011), most of the volunteers who participated in this study were females (140 = 65.7%). The age distribution of the participants was consistent with findings from the Australian Council of Social Service (2009), which suggested that older people (aged 43 and above) participate more in voluntary services than younger people do. Most of the respondents volunteered three to four hours per week and had been with the organisation for three to five years. Table 1 shows the means, standard deviations, and correlation coefficients for each of the variables. Prior to hypotheses testing it was important to ensure that the items used represented the theoretical constructs they were intended to measure (Schumacker and Lomax, 2004). The measures were evaluated with a factor analysis set with a factor loading of .50 as the cut-off point. The 25 questions in the questionnaires revealed eight latent variables with eigenvalues greater than one. These factors explained 78 per cent of the variance, with the first factor accounting for 10.07 per cent of the variance. The Bartlett's test of sphericity was significant (with a Chi-square value of 3220.611, p = .001). The Kaiser-Meyer-Olkin measure of sampling adequacy was .875, which is above the minimum .6 requirement (Hair et al., 2010;Kline, 2011). Multicollinearity and common method bias were not a problem because none of the correlations were above .90 (Pavlou et al., 2006). In addition, Harmon's single factor test shows that the degree of variance accounted for by one factor was 17.8 per cent, which is lower than the 60 to 70 per cent point of concern (Fuller et al., 2016). As the unrotated exploratory factor analysis did not show that a single factor accounted for most of the variances, the common method bias was not considered to be a problem.

Data Analysis and Results
In addition, both the average variance values (AVE) and composite reliability (CR) for the eight latent variables of this study were above the minimum recommended value of .50 (see Hair et al., 2010;Kline, 2011). These values provide additional support for the convergence of the items and confirm that all the latent variables are distinct from each other (discriminant validity). A simple linear regression was used to explore H1 and a multiple regression was used for hypotheses H2 and H3. The mediation analyses were based on Baron and Kenny's (1986) conditions of mediation.
To ensure that the mediation analysis process fulfilled the conditions stated by Baron and Kenny (1986), a series of multiple regressions were explored for each of the hypotheses. The first condition, which was to test for the effect of the independent variables (POS) on the mediators, was met by regressing the mediators on the independent variable. The second condition, which was to test for the effect of the independent variable on the dependent variable, was determined by regressing the dependent variable on the independent variable. The third condition, which was to test for the effect of the mediators on the dependent variable, was established by regressing the dependent variable on each of the motive fulfilment. Lastly, the fourth condition, which was to test for mediators' effects, was met by regressing the dependent variable on the independent variable and the mediators. However, since the second condition would have been met with the analysis of the direct relationship between the independent and the dependent variable (H1), only the other three steps were performed. Thus, three separate steps are shown in the tables under the mediation analysis.
H1 was supported as the relationship between POS and affective commitment was positive and statistically significant (R 2 = .406, F = 47.694, p < .0001). The result is shown in Table 3. In terms of H2, the results provide support for the acceptance of the hypothesis because the relationship between POS and each motive fulfilment was positive and statistically significant. The result of each motive fulfilment is shown in Table 4.
H3 was partially supported because three out of the six motive fulfilment variables (that is, values, understanding, and enhancement motives) have a positive and significant effect on the impact of POS on affective commitment. The beta (β) weight of POS dropped from .599 to .310 after the mediating variables were included in the multiple regression model. However, the fulfilment of career, social, and protective motives were not significant. The steps taken to ensure that the model met all the conditions of mediation analysis are shown in Table 4.

The Sobel Tests
To test whether the change made by each of the mediators was significant, a Sobel test, which is a formal test of the indirect effect of a third variable, was run. The Sobel test directly addresses the question of whether the total effect of an independent variable on a dependent variable is significantly reduced when a mediating variable is added to the model (Preacher and Hayes, 2004). This is done by calculating the product coefficients of the independent and dependent variables. Apart from the fact that the test directly addresses the question of mediation by meeting Baron and Kenny's (1986) criteria stated above, the use of a product test coefficients strategy has greater statistical power than the multiple regression test and any other method of calculating mediation (MacKinnon et al., 2002). In addition, the use of the Sobel test helps to minimise 'Type Ӏ' and 'Type ӀӀ' errors, which could occur in Baron and Kenny's multiple regressions (MacKinnon et al., 2002;Preacher and Hayes, 2004). The results of the Sobel test confirm that three of the motive fulfilment variables act as significant mediators, and these results are presented in Table 5.

Discussion
The purpose of this study was to examine the influence of POS on affective commitment and to investigate whether motive fulfilment would mediate the relationship between POS and volunteers' affective commitment to NPOs in Australia. Consistent with previous studies (Addae et al., 2006;Farmer and Fedor, 1999;Maertz et al., 2007), the findings support hypothesis H1 that POS has a direct and significant impact on volunteers' affective commitment. Furthermore, it also provides support for the indirect effect of POS through some of the motive fulfilment variables (values, understanding, and enhancement motives) on affective commitment. The present study's findings, with respect to the direct relationship between POS and affective commitment, are not only consistent with previous results but extend existing knowledge about the influence of POS on volunteers' affective commitment in NPOs. For example, the findings are consistent with past findings (see Eisenberger et al., 2002;Maertz et al., 2007) that POS predicts affective commitment.
The findings of this study that POS (H2) have a direct and significant impact on volunteers' motive fulfilment shows the importance of POS as an antecedent of motive fulfilment in the context of volunteers. This result does not only provide support to previous studies but also reinforces the view that the perception of support from the organisation is important for volunteers because their services are based on a relational contract that does not involve remuneration (Boezeman and Ellemers, 2007;Farmer and Fedor, 1999;Garner and Garner, 2011). In this respect, the statistical analysis of the effect of POS on motive fulfilment accounts for above 25 per cent of the variance in each of the motive fulfilment components except for protective motive fulfilment. The indirect effect of POS on affective commitment through value motive (β =.184), enhancement motive (.185), and understanding motive (.165) fulfilment suggests that affective commitment would increase when the organisation provides a supportive work environment where policies and procedures enable volunteers to reach out to people in need. These results show that supporting the personal growth of volunteers in areas such as knowledge and skill improvement increases volunteers' perceptions of organisational support.
In addition, understanding and enhancement motives are closely related to what Deci and Ryan (2000) refer to as autonomy and competence needs, which have been identified as individuals' most important needs regardless of their demographic differences. These findings support the argument that any social environment (for instance, the social environment in an organisation) that facilitates the satisfaction of these needs will increase the likelihood of positive workplace outcomes. In this respect, volunteers with a sense of autonomy over the activities given in a community NPO are likely to have increased self-esteem because some measures of independence are attached to what they do as volunteers. Competence relates to the understanding motive, as the acquisition of more skills and knowledge improves one's aptitude. Hence, for volunteers who desire such psychological support, the satisfaction of these motives (understanding and enhancement) increases their perceptions of organisational support.
Furthermore, the findings of this study confirm those of other studies that the need for fulfilment partially mediates the association between POS and affective commitment (Lee and Peccei, 2007). Another possible reason why the fulfilment of both understanding and enhancement motives are significant in the relationship between POS and affective commitment is that affective commitment to the organisation increases when socio-emotional needs such as esteem, approval, and affiliation are met (Rhoades et al., 2001;Maertz et al., 2007;Su et al., 2009). According to Armeli et al. (1998) and Rhoades and Eisenberger (2002), continuous exchanges of rewards that fulfil the important socio-emotional needs of individuals will result in the development of real emotional links with the organisation due to increased feelings of psychological fulfilment. In this way, the positive impact of POS on affective commitment depends on the extent to which important socio-emotional needs are fulfilled. Hence, volunteer commitment has been associated with the fulfilment of their motives.
On the effect of POS's indirect impact on volunteers' affective commitment, there have been limited empirical findings about how managements' actions influence volunteers' workplace outcomes in community NPOs through motive fulfilment. One study that demonstrated somewhat related findings is that of Boezeman and Ellemers (2007) who examined the perceptions of Dutch volunteers working in NPOs. Their study showed that the type of POS (emotion-oriented and task-oriented organisation support) was significantly related to respect for a volunteer organisation and indirectly and positively associated with organisational commitment through respect. The lack of studies regarding the indirect relationship between POS and volunteer affective commitment thus means that the findings of this study contribute new knowledge to the literature by showing the indirect effects of POS on volunteers' affective commitment through the fulfilment of values (altruism), understanding, and enhancement motives.
From the perspective of the theoretical framework (SET) used in this study, the results from this study contribute to the third proposition of Homans (1961) that the exchange of valuable resources results in high reciprocity. In other words, for the volunteers in the community NPOs investigated, reciprocity depends on the fulfilment of important motives. This suggests that providing clear processes and procedures for volunteers' job activities and supporting the personal growth of volunteers in areas such as knowledge and skill improvement will increase their perceptions of being supported. These types of support from the organisation are important rewards because they fulfil the volunteers' functional motives, which in turn causes them to feel obligated to reciprocate by being affectively committed.
As shown in the analysis, the fulfilment of some egoistic motives did not act as a significant mediator in the relationship between POS and affective commitment. Protective motive, social motive, and career motive fulfilment were not significant in the association between POS and affective commitment. One of the possible reasons for the above findings is that volunteers' perceptions of motive fulfilment rely on a complex set of personal cognitive processes and experiences. These perceptions shape their decision-making processes and behaviours. Thus, factors such as individual differences, organisational culture, and organisational context might have affected the results. For example, Mannino et al. (2011) emphasise that while volunteers' actions are due to their relatively altruistic or other-oriented motives, the possibility exists that during their work, they may meet other local community members, and as a result, they may become more interested in expanding their social networks. Mannino et al.'s (2011) assertion is an example of how volunteers' motives may evolve from an initial motive to other motives due to a context that presents itself in the organisation. This should also be considered against the fact that the fulfilment of both altruistic and egoistic motives only had a significant partial mediating influence on the relationships examined. The fulfilment of altruistic and egoistic motives did not eliminate the impact of the predictor completely. Partial mediation is an indication that other factors may be influencing the relationships, and this may also explain why the career, social, and protective motives were not significant as mediators in this study.
In addition, Okun and Schultz (2003) found that as age increases, volunteers' motivations with respect to career benefits decrease and the importance of social networking, which is a feature of social capital, increases. Thus, it is not surprising that the fulfilment of career motives did not have a significant impact on the association between management and affective commitment because career benefits may not be important for older volunteers. Hence, the fulfilment of career motives might not have been of much importance to most of the volunteers in the community NPOs in Queensland, Australia who took part in this study. This study has several practical implications for management interested in increasing volunteers' affective commitment. On a practical level, the findings of this study have confirmed that a supportive work environment fosters volunteers' positive workplace experiences. As such, the mediation framework provides useful information that will help community NPOs to develop policies that will nurture volunteers' interests to gain their commitment.
In the context of this study, this means providing a supportive structure and guidance that will lead to the satisfaction of three basic psychological needs: A sense of volition; the ability to behave in line with self-values, beliefs, and preferences to achieve desired outcomes; and the experience of love and care from other social groups. The satisfaction of these salient motives in relation to volunteers will increase volunteers' positive work experiences and increase their commitment. What is clear from this study is that there are no fixed guidelines for managing volunteers in community NPOs. Rather, management needs to take volunteers' motives into consideration when designing their models of volunteer management to be able to deal with challenges of volunteers' behaviours. As indicated by the findings of the study, it is critical that NPOs provide a supportive work environment that has been identified as antecedent of the workplace outcomes (affective commitment). This requires good organisational policies that provide managers with the latitude to manage the resources at their disposal. These findings will sensitise NPOs towards the roles of volunteer motives and the abiding concerns of the volunteers they seek to recruit.
While focusing on these three motives, fulfilment may sound appealing to organisations focusing on enhancing affective commitment. The findings of this study indicate that community NPOs would need to use such an approach with caution. In a nutshell, given what this study has revealed, volunteer managers should not ignore volunteer motives, including activities that would result in fulfilment of other benefits such as protective, social, and career motives because of their direct effects on affective commitment despite not being effective as mediators.

Conclusion
As this study and the literature have shown, studies on POS are fundamental to the understanding of employees' workplace behaviours which help organisations to achieve their objectives. Given the findings of the study, supportive work environments that show volunteers that the organisation cares about their motives for volunteering will encourage volunteers to be affectively committed to their organisations. The findings in this study highlighted the positive relationships between POS and the affective commitment of volunteers in community NPOs in Queensland, Australia; and the analyses of the effect of motive fulfilment as intervening variables in this study offers a unique perspective on SET as an analytic lens. This study used a sample of respondents who are volunteering in one type of volunteer organisation, specifically, community NPOs. Although the participants were drawn from diverse backgrounds, there is need for caution when extrapolating the findings to other categories of NPOs such as sport/recreational NPOs and emergency service NPOs. It is likely that the calibre of volunteers and the requirements for being a volunteer in these categories of NPOs may be different from community NPOs. These differences may affect the generalisability of the findings of this study.
This study is important because the questionnaire used was based on reliable tools that have been previously validated. A strong point of the study is that the factor analysis results showed that items loaded strongly onto the eight factors used in the analysis, and there was excellent internal reliability of the scales for each of the constructs as indicated by their Cronbach alphas. In addition, the fact that the findings are consistent with others' findings also suggests a degree of reliability and validity. The study, therefore, warrants consideration in the future management of volunteers in NPOs.