Psychological capital as a moderator in the relationship between occupational stress and organisational citizenship behaviour among Nigerian

Scholars have linked challenges that are related to employee performance in current employment with high levels of occupational stress (Baxter, 2010; Laschinger, 2011; Shafaghat, Zarchi, & Kavosi, 2018). In the same manner, studies have shown that occupational stress is significantly related to both task-related work behaviour and non-task-related work behaviour of employees (Adebiyi, 2013; Arogundade & Lawal, 2016; Niks, de Jonge, Gevers, & Houtman, 2018). The World Health Organization (WHO) has also reported occupational stress as a global epidemic (WHO, 2010). Obviously, the consequence of an increasingly strenuous work environment is evident in Nigerian work settings, as cases of job dissatisfaction, a high rate of absenteeism, employee intention to quit, labour turnover and poor job performance (contrast to organisational citizenship behaviour) remain evident among graduate employees in Nigeria (Adebayo & Ogunsina, 2011; Adebiyi, 2013; Adetayo, Ajani, & Olabisi, 2014; Arogundade & Lawal, 2016).


Introduction
Scholars have linked challenges that are related to employee performance in current employment with high levels of occupational stress (Baxter, 2010;Laschinger, 2011;Shafaghat, Zarchi, & Kavosi, 2018).In the same manner, studies have shown that occupational stress is significantly related to both task-related work behaviour and non-task-related work behaviour of employees (Adebiyi, 2013; Arogundade & Lawal, 2016; Niks, de Jonge, Gevers, & Houtman, 2018).The World Health Organization (WHO) has also reported occupational stress as a global epidemic (WHO, 2010).Obviously, the consequence of an increasingly strenuous work environment is evident in Nigerian work settings, as cases of job dissatisfaction, a high rate of absenteeism, employee intention to quit, labour turnover and poor job performance (contrast to organisational citizenship behaviour) remain evident among graduate employees in Nigeria (Adebayo & Ogunsina, 2011;Adebiyi, 2013; Adetayo, Ajani, & Olabisi, 2014; Arogundade & Lawal, 2016).turnover intention, turnover behaviour and employee productivity (American Psychological Association, 2013; Goh, Pfeffer, & Zenios, 2015).Hence, few scientific investigations have been conducted to devise psychological intervention strategies to ameliorate the situation and ensure organisational citizenship behaviour (Ahmad, Hussain, Saleem, Qureshi, & Mufti, 2015; Niks et al. 2018).Furthermore, although there is an increasing consideration of the phenomenon of organisational citizenship behaviour by researchers, a thorough review of the literature shows a lack of agreement about the scope of the concept (Farzianpour, Foroushani, Kamjoo, & Hosseini, 2011).However, the current study sought to empirically examine the moderating role of psychological capital (PsyCap) in the relationship between occupational stress and organisational citizenship behaviour in order to fill the existing vacuum identified in the literature.

Research purpose
The purpose of the study is twofold.Firstly, the study seeks to examine the nature of relationship between occupational stress and organisational citizenship behaviour.Secondly, the study seeks to investigate if there is a significant moderating role of PsyCap in the relationship between occupational stress and organisational citizenship behaviour.

Organisational citizenship behaviour
Organisational citizenship behaviour is an essential phenomenon in the formal work setting because of its potency to facilitate interpersonal relationships among employees, and also to increase organisational performance (Kumari & Thapliyal, 2017;Pradhan, Jena, & Bhattacharya, 2016).Organisational citizenship behaviour is an alternative form of performance behaviour, which is differentiated from the traditional performance that relies heavily on official assignments and tasks (Karolidis, 2016).For instance, having subordinates who are highly engaged in organisational citizenship may improve managers' efficiency by allowing them to devote a greater amount of time to long-range planning matters.Hence, managers, employees and the organisations at large benefit from the positive behaviours (Lelei, Chepkwony, & Ambrose, 2016; Nawazi & Gomes, 2018).These behaviours are explained by concepts such as pro-social behaviours, extra-role behaviours, contextual performance, spontaneous behaviours or organisational citizenship behaviour.

Occupational stress
Occupational stress is a negative career-related concept that generates concerns among career holders, and it has the ability to influence individual and organisational outcomes (Beheshtifar & Nazarian, 2013).In other words, occupational stress is a negative phenomenon, the occurrence of which often stimulates an unpleasant response to the work environment making it appear threatening to the employees.Moreover, prolonged occupational stress could manifest itself physically, emotionally and psychologically in the lives of the affected employees.
The commonly reported physical symptom of occupational stress is a headache, which makes the affected employees unconsciously tense in their necks, foreheads and shoulder muscles (Chandra & Parvez, 2016).The other known symptoms of occupation stress are digestive problems, ulcers, hypertension, anxiety and inordinate sweating, coronary illness, strokes and even male pattern baldness (Chandra & Parvez, 2016).Emotionally, an affected employee frequently displays nervousness, outrage, depression, fractiousness, frustration to ordinary issues, dementia and an absence of focus for any assignment, because the mind of the individual is negatively impacted.The psychological manifestations of occupational stress, on the other hand, include withdrawal from society, phobias, compulsive behaviours, eating disorders and night fears (Chandra & Parvez, 2016).

Psychological capital
The term 'PsyCap' is a composite construct that is defined according to Luthans, Avolio, Avey and Norman (2007) as: a person's positive mental state of improvement, which is described by: (1) having confidence (self-efficacy) to take on and put in the needed effort so as to prosper at challenging responsibilities; (2) making a positive attribution (optimism) about succeeding now and in the future; (3) determining toward goals and, when necessary, diverting ways to objectives (hope) with a specific end goal to succeed; and (4) when affected by issues and afflictions, managing, enduring and even going past (resilience) to reach success.(p. 3) According to Aliyev and Tunc (2015), PsyCap is a collection of abilities such as self-efficacy, optimism and endurance that are open to improvement, and it implies more than the collection of the aforementioned skills.Specifically, capital signifies the quality of individuals' assets (human capital) as well as in connection with other constructs such as social capital, cultural capital and intellectual capital (Amunkete, 2015).The term 'PsyCap' also denotes individual motivational inclinations that accumulate through desirable psychological concepts such as optimism, resilience, hope and efficacy (Luthans et al., 2007).Besides, PsyCap is recognised in the situation of a venture in psychic resources that results in getting realistic incentives from the current moment while also brightening the prospect of future benefits.It is about the condition of the segment of an individual's inner life (Amunkete, 2015).

Relationship between occupational stress and organisational citizenship behaviour
In a recent descriptive correlational study (Nourani, Kohansal, Esmaily, & Hooshmand, 2016) on the relationship between organisational citizenship behaviour and occupational stress among 122 midwives at Mashhad, Iran, it was found that there is a significant negative association between organisational citizenship behaviour and occupational stress.Likewise, Arogundade and Lawal (2016) investigated the influence of perceived occupational stress on the organisational citizenship behaviour among 300 male and female bankers in Lagos, Nigeria, using a simple random sampling technique.Although the results of the study revealed that there is no significant difference in the levels of organisational citizenship behaviour that were exhibited by bankers with higher stress levels and those with lower stress levels, there is an inverse relationship between occupational stress and organisational citizenship behaviour.
Moreover, Soo and Ali (2016) studied the linkage between occupational stress and organisational citizenship behaviour among a sample of 472 bankers in Malaysia and found that there is a significant negative impact of occupational stress on organisational citizenship behaviour.In the same vein, Gregory, Yitzhak and Steffen (2016) scientifically examined the proposed need to distinguish between self-initiated and organisationally imposed overload in studies of work stress, using three samples, which consisted of 116 male and female full-time employed students in three countries, some nursing staff of six private hospitals in Switzerland and 161 middle manager-supervisor dyads in Switzerland.The study revealed in its findings that self-initiated imposed overload is significantly, positively related to organisational citizenship behaviour, but organisationally imposed overload is not a significant predictor of organisational citizenship behaviour.Furthermore, Ikonne and Madukoma (2016) conducted a survey on the relationship among organisational citizenship behaviour, job stress and satisfaction among 109 librarians in some selected universities around the south-west region of Nigeria and found that there is a significant negative relationship between organisational citizenship behaviour and job stress.In addition, Uzonwanne (2014) conducted a survey research on depression, anxiety and stress as correlates of organisational citizenship behaviour, using the accidental sampling technique to sample 151 female and 149 male employees of oil and gas companies in Ogun State, Nigeria.The outcomes of their research showed that there is a significant positive relationship between occupational stress and organisational citizenship behaviour.The findings of the study also indicated that although there was a statistical positive relationship between the two variables, the observed positive relationship was weak considering the r value of 0.118, which is close to 0.

Psychological capital as a moderator in the relationship between occupational stress and organisational citizenship behaviour
Aybas and Acar (2017) surveyed the mediating and moderating roles of PsyCap in the effects of opportunity enhancing human resource (HR) practices and working conditions on work engagement among 555 white-collar employees of private companies from different sectors in Turkey by using a convenience sampling method and a validated questionnaire and sampled the views of respondents about the variables under consideration in the study.The results of the statistical analysis of data showed that PsyCap partially moderated and mediated the effects of opportunity enhancing HR practices and working conditions on work engagement.
Likewise, Wang, Liu, Zou, Hao and Wu (2017) conducted a cross-sectional survey research that investigated the mediating role of PsyCap on occupational stress, organisational support and work engagement among a sample of 1016 female nurses that was drawn from the population of nurses in the general hospitals in Shenyang, Liaoning Province, China.A validated questionnaire was used to collect data from all the participants in the study.The research findings showed that PsyCap and its components of hope and optimism are significant mediators of the relationships among work stress, work engagement and rewards.
In addition, Shaheen, Bukhari and Adil (2016) surveyed the moderating role of PsyCap in the relationship between organisational support and organisational citizenship behaviour among a sample of 325 employees in public and private sector banks of Islamabad and Rawalpindi cities in Pakistan by using a convenience sampling technique and a validated questionnaire to gather information from the participants.The study discovered and established from its findings that PsyCap significantly enhanced the observed positive relationship between organisational support and organisational citizenship behaviour.
Correspondingly, Li et al. (2015) studied the mediating role of PsyCap on the association between occupational stress and burnout among a sample of 1239 male and female bankers drawn from the population of bankers in the state-owned banks in Liaoning in China by using a random sampling technique.The study adopted a cross-sectional survey research design and used a validated questionnaire to collect data from the participants.The findings of the study indicated that PsyCap is generally a mediator between occupational stress and job burnout among Chinese bank employees.

Conceptual model
Based on the past studies reviewed and on logical grounds, a conceptual model was developed indicating the hypothesised relationship between occupational stress and organisational citizenship behaviour, and the moderating role of PsyCap.Organisational citizenship behaviour is depicted as the dependent variable, while occupational stress is the independent variable, whereas PsyCap is shown as the moderating variable.The conceptual model, demonstrated in Figure 1 relationship between occupational stress and organisational citizenship behaviour.

Statement of hypotheses
Hypothesis 1 H 0 : Occupational stress is not significantly positively correlated with organisational citizenship behaviour.
H 1 : Occupational stress is significantly positively correlated with organisational citizenship behaviour.

Hypothesis 2
H 0 : Psychological capital is not a significant moderator of the relationship between occupational stress and organisational citizenship behaviour.
H 1 : Psychological capital is a significant moderator of the relationship between occupational stress and organisational citizenship behaviour.

Research design, sample and procedure
The study adopted a positivist explanatory cross-sectional (survey) research design.The explanatory cross-sectional (survey) research was considered appropriate for the study because the research used the positivist approach by means of quantitative data generation and hypotheses testing (Bhattacherjee, 2012).The chosen research design was also considered appropriate in the study because the study cut across the private and public sectors of the national economy, and thus incorporated diverse industries.

Measuring instruments
Three established scales of measurement were used to assess PsyCap, occupational stress and organisational citizenship behaviour.

Psychological capital
A 24-item scale of PsyCap that was developed and validated by Luthans et al. ( 2007) was utilised to measure PsyCap.
The construct consisted of self-efficacy, hope-state, optimismstate and resilience-state sub-scales, with a five-point Likerttype response format ranging from 1 (strongly disagree) to 5 (strongly agree).The authors reported a Cronbach's alpha coefficient score of 0.91 for the scale.However, the outcome of the pilot factor analysis of this study reduced the scale item to 21, and yielded Cronbach's alpha coefficient scores of 0.88 (self-efficacy), 0.91 (hope), 0.85 (resilience), 0.67 (optimism) and 0.94 for the whole scale of psychological capital, while the main study's factor analysis yielded a Cronbach's alpha coefficient score of 0.85 for the whole scale of PsyCap (See Appendices 1-3 for details).

Occupational stress
A nine-item scale of job stress that was developed and validated by Jamal and Baba (1992) was utilised to measure occupational stress.The measure was designed with a fivepoint Likert-type response format ranging from 1 (strongly disagree) to 5 (strongly agree).The authors reported a Cronbach's alpha coefficient score of 0.83 for the scale.However, the outcome of the pilot factor analysis of this study reduced the scale item to seven and yielded Cronbach's alpha coefficient score of 0.81, while the main study's factor analysis yielded a Cronbach's alpha coefficient score of 0.80 for the measure of occupational stress (See appendices 1-3 for details).reported the following Cronbach's alpha coefficients for the scale: altruism = 0.81, conscientiousness = 0.73, civic virtue = 0.73 and 0.84 for the whole scale of organisational citizenship behaviour.However, the outcome of the pilot factor analysis of this study reduced the scale item to 13, and yielded Cronbach's alpha coefficients of 0.88 (altruism), 0.81 (conscientiousness), 0.86 (civic virtue) and 0.93 for the whole scale of organisational citizenship behaviour, while the main study's factor analysis yielded a Cronbach's alpha coefficient score of 0.82 for the whole scale of organisational citizenship behaviour (See appendices 1-3 for details).

Statistical analysis of data
The data generated from 1532 screened questionnaires were analysed based on the hypotheses stated, using version 20 of the Statistical Package for the Social Sciences (SPSS).Hypothesis 1 was analysed, using Pearson correlation analysis.Hypothesis 2 was analysed using multiple regression analysis, while the percentage, mean, standard deviation (SD) and the frequency of the biographical and occupational data were determined by the descriptive statistics.

Ethical consideration
Voluntary participation in the study was sought through a letter of consent, signed by each of the participants.The participants were informed about the importance of the study as the findings of the study may positively influence the government policy helping in improving their conditions of employment and service.Moreover, assurance was given to the participants with respect to confidentiality of all information supplied.Furthermore, the participants were instructed not to indicate any means of identification such as name, identity number and organisational affiliation.With utmost sense of sincerity, information concerning the study and its outcomes was accurately submitted to the appropriate institutions.Thus, it was ensured that no instances of misleading actions were demonstrated in the course of the study.The researchers also ensured that the study was conducted in a conducive environment such that it would not expose the participants to any physical or psychological hazard.The Research Ethics Committee of University of Fort Hare granted approval for ethical clearance of the study (certificate reference number: MJO071SADE01).

Research results
The results in Table 1 show the levels at which the participants possessed each of the variables of consideration in the study.For instance, the results of descriptive statistics show that the participants demonstrated a higher level of PsyCap, X̅ = 60.482,SD = 8.493.The results imply that the participants in the study are positively oriented about themselves.
Similarly, the results in Table 1 show that participants expressed a high level of organisational citizenship behaviour X̅ = 52.389,SD = 6.949), which also indicates that the participants are highly interested in helping their colleagues at work, at the same time ensuring that their personal and organisational goals are achieved.Likewise, the results in Table 1 further show that the participants expressed a significant amount of occupational stress (X̅ = 24.354,SD = 5.402).The results mean that the participants have experienced some amount of occupational stress.The results further reveal that the participants expressed significantly higher levels of civic virtue (X̅ = 20.584,SD = 3.178), hope (X̅ = 20.528,SD = 3.405), self-efficacy (X̅ = 20.385,SD = 3.546), altruism (X̅ = 20.002,SD = 3.254), resilience (X̅ = 15.354,SD = 2.595), conscientiousness (X̅ = 11.804,SD = 1.971) and optimism (X̅ = 8.042, SD = 1.653).
Hypothesis 1 was analysed by using Pearson's correlation analysis.The results of the analysis are presented in Table 2.
The data in Table 2 show that there is a positive relationship between OS and OCB (r = 0.070, p = 0.01).Even though there is a positive relationship observed between OS and OCB, the level of the observed positive relationship between the two aforementioned variables is feeble, considering the given significance value, 0.006 = 0.01 (approximated to two decimal points), which is exactly the maximum limit of acceptable value of significance at the 0.01 level (2-tailed).Therefore, based on the results and interpretations above, Hypothesis 1, H 0 , is rejected, while Hypothesis 1, H 1, is accepted.Figure 2 depicts the relationship between OS and OCB.
The results in Table 3 show that PsyCap is a significant moderator of the relationship between OS and organisational citizenship behaviour, F(2.1529) = 8.514; R 2 = 0.011; p < 0.01.The results also indicate that occupational stress independently influences organisational citizenship behaviour (β = 0.070; t = 2.738; p < 0.05).However, when compared the beta value obtained from the direct influence of occupation stress (β = 0.070) with that of the moderating influence of PsyCap (β = 0.064) in the relationship between OS and organisational citizenship behaviour, the result indicates that PsyCap demonstrated a significant moderating influence in the observed relationship between OS and OCB by significantly reducing the undesirable direct influence of occupation stress on organisational citizenship behaviour.
The results in Table 3 further show that the moderating role of PsyCap accounts for only 1% of the total variance in the relationship between OS and OCB.It thus implies that many other factors that were not considered in the study could be responsible for the remaining 99% variance in the relationship between OS and OCB.Although the R value, on the other hand, is higher (0.105), which if considered, it implies that PsyCap accounts for as much as 10% of the total variance in the relationship between OS and OCB, but it is not as reliable as the R 2 value even though it looks greater, because the statistical principle of regression theory emphasizes the fact that only the R 2 guarantees error-free values.In view of the above results and its interpretations, Hypothesis 2, H 0 , is rejected, while the H 1 is accepted.Figure 3 depicts the picture of PsyCap moderating the relationship between OS and organisational citizenship behaviour.

Discussion
The results presented established the hypothesised relationship and moderation in the conceptual model (Figure 1).A weak positive relationship was found existing between OS and OCB.This explains that though there is an indication of a positive relationship between OS and OCB, but the observed level of positive relationship between the two variables is not reliable enough.Thus, perhaps, it requires the introduction of one or more other positive variables to serve as moderators or mediators in order to yield a more significant and reliable relationship.These findings corroborate the reports of Uzonwanne (2014), which states that there is a weak positive relationship between OS and OCB.Similarly, Soo and Ali (2016) report further that self-initiated imposed work overload is significantly, positively related to organisational citizenship behaviour, but organisationally imposed overload is not a significant predictor of organisational citizenship behaviour.
In terms of moderation, PsyCap was found to have a significant level of moderating role in the observed positive relationship between OS and OCB.Although the results

Limitations of the study and suggestions for future research
The first noticeable shortcoming of this research relates to bias in the approach of data collection.The research only adopted the quantitative method, which limited the opinions of research respondents to the response options provided to statements in the questionnaire.This study therefore suggests that future studies should consider adopting more than one method of data collection.The second acknowledged limitation of this study is that only one moderating variable was considered in the structured model.

Recommendations
In view of the above discussion of the findings, the researchers make the following practical recommendations: • The tertiary institutions' management, most especially of the universities, should incorporate in their academic curricula some practical simulated work exercise that will pre-expose the graduating students to the challenges at the world of work.This will build their psyche and make them mentally and emotionally ready to overcome any stressful situation that may come in their way, even in the cause of discharging of career duties or responsibilities through the positivism approach.This can be achieved by a deliberate inclusion of moderately difficult practical group assignments in the syllabus that will task each student in a group to proactively think 'outside the box' and proffer visible solutions in the form of suggestions to the problems at hand.By so doing, the students will develop reasonable levels of hope, resilience, optimism, self-efficacy and empathy along with the acquired theoretical knowledge of their disciplines, while the universities can also boast of producing capable graduates who will fit perfectly into the realities of the world of work and promptly deliver.• The model of relationship between OS and organisational citizenship behaviour, propounded in this study, should be adopted and applied by teachers, lecturers, seminar facilitators, workshop trainers, supervisors and managers during their coaching or training sessions.Specifically, the focus should be on training the individual employees or graduates to discover their covert behavioural endowments such as PsyCap and make them refined through a systematic training process that converts the covert behavioural gifts into overt psychological assets in the form of demonstrable managerial competencies, which can enhance their performance on the job, and also enable them to be pro-social among colleagues in the work settings.

Conclusion
This study concludes that there is a positive relationship between OS and organisational citizenship behaviour.It also concludes that PsyCap is a significant moderator of the relationship between OS and organisational citizenship behaviour.The researchers therefore finally state that the study findings contribute specifically to the existing literature on occupational stress, organisational citizenship behaviour and also to the literature on employee performance management.

FIGURE 1 :
FIGURE 1: Psychological capital as a moderator of the relationship between occupational stress and organisational citizenship behaviour.

A 15 -
item modified version of Podsakoff, Mackenzie, Moorman and Fetter's (1990) organisational citizenship behaviour questionnaire by Argentero, Cortese and Ferretti (2008) was utilised to measure organisational citizenship behaviour.The construct consisted of altruism, conscientiousness and civic virtue sub-scales, with a fivepoint Likert-type response format ranging from 1 (Strongly disagree) to 5 (Strongly agree).Argentero et al. (2008) Firstly, the convenience sampling technique was applied in selecting three most suitable states (Oyo, Osun and Lagos States) out of the 36 states in Nigeria, as the sites of the field work.The rationale for selecting the three states is that each of them houses one or the other of the renowned public and private universities (University of Ibadan, Obafemi Awolowo University and the Pan-Atlantic University) where the study samples were offered part-time postgraduate admissions for MBA programmes as workingclass postgraduate students with a minimum of 3-year employment experience.Another reason for adopting the convenience sampling technique was because the fieldwork became easier when the participants were met in groups at conducive places such as in the lecture rooms and relaxation centres within the university premises.Furthermore, as the study was designed only for the graduate employees, the purposive sampling technique was also introduced and applied to ensure that participants in the study were employed during the period of the field work, and that they were graduates of universities and polytechnics.
population sampled being a true representation of the study's targeted population.Thus, a total of 1532 male and female graduate employees formed the sample size of the study.In addition, the convenience and purposive types of nonprobability sampling technique were employed in selecting participants for the study.

TABLE 1 :
Descriptive analysis showing the mean and standard deviation among organisational citizenship behaviour, the three dimensions of organisational citizenship behaviour, psychological capital, the four dimensions of psychological capital and occupational stress.
Psychological capital as a moderator of the relationship between occupational stress and organisational citizenship behaviour.

TABLE 3 :
Summary of multiple regression analysis showing the moderating role of psychological capital in the relationship between occupational stress and organisational citizenship behaviour.

TABLE 2 :
Summary of Pearson's correlation analysis showing the relationship between occupational stress and organisational citizenship behaviour.
Note: Hypothesis 2 was analysed by using multiple regression analysis.The results of the analysis are presented in Table3.*,Correlation is significant at the 0.01 level(2-tailed).FIGURE 2: Relationship between occupational stress and organisational citizenship behaviour.

Section: D No. Statements Strongly disagree Disagree Rarely agree Agree Strongly agree 34
. I willingly help others who have work-related problems.35.I am always ready to give a helping hand to those around me. 36.I help others who have heavy work load.37. I help others who have been absent.38.I guide new people even though it is not required.39.I take steps to try to avoid problems with other workers.40.I attend functions that are not required, but help the company image.41.I attend meetings that are not mandatory, but important.42.I read and keep up with organisation announcements, memos and so on.43.I keep abreast of changes in the organisation.44.I respect company rules and policies even when no one is watching me.45.I do not take extra breaks.46.I believe in giving an honest day's work for an honest day's pay.47.I do my job without constant requests from my boss.48.I am one of the most conscientious employees.

No. Statements Strongly disagree Disagree Rarely agree Agree Strongly agree 24
. I willingly help others who have work-related problems.25.I am always ready to give a helping hand to those around me. 26.I help others who have heavy work load.27.I help others who have been absent.28.I guide new people even though it is not required.29.I attend meetings that are not mandatory, but important.30.I read and keep up with organisation announcements, memos and so on.31.I keep abreast of changes in the organisation.32.I respect company rules and policies even when no one is watching me.33.I do not take extra breaks.34.I believe in giving an honest day's work for an honest day's pay.35.I do my job constant requests from my boss.36.I am one of the most conscientious employees.