The Psychological Contract Theory on Individual and Work-Related Outcomes: A Systematic Literature Review (SLR)

The aim of this article was to present evaluation-based themes related to the psychological contract theory, specifying the influence this theory has on individual and work-related outcomes as reported in articles published between January 2009 and December 2020 through a systematic literature review. The individual and work-related outcomes in this study lack a systematic literature review (SLR) despite enormous number of published articles with these outcomes. A systematic literature review method was used to gather data, which was analysed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Following the PRISMA guidelines, 45 eligible studies were included from various industries and countries, and findings were reported using descriptive synthesis and tabulation. Scoping evaluation was used to capture the state of current, relevant literature, to acknowledge gaps, and make recommendations for upcoming studies. The findings of the systematic literature review showed that perceived psychological contract is embedded in the fulfilment of the employer obligations, which influences the employees’ perception of the state of the psychological contract, and both the employee and employer obligations need to be precise. This study aimed at aggregating and collecting fragmented academic knowledge on the individual and work-related outcomes related to the psychological contract. This systematic literature review emphasises the importance of the psychological contract in organisations in managing the employment relationship. The review made suggestions for practical implications for organisations, limitations and recommendations for future studies.


Introduction
The psychological contract theory (PCT) is entrenched in the growth and the preservation of relations that develop at work (Kutaula et al., 2020), which Bal and Hornung (2019) had previously found that the understanding of the psychological contract (PC) is a prevalent area of importance and research interest because of its impact on employment relations. Rousseau et al (2018) acknowledged that the PCT has been dominated by content and evaluation theory and has been studied significantly, but there is still a lack of validity when applied to the PC. In earlier research Rosseau et al (2013) explained that PCT is regarded as the content and dynamics that are found in the employment relationships and that PCT is the reflection of the perceived and reciprocated obligations between employers and their employees and how these tend to influence attitudes and behaviours towards each other. This systematic literature review embarked on a research to find how valid the PCT is when applied in different industries of different cultures. Kutaula et al (2020) found that the PC's transitional and balanced form has limited research output. This finding provided motivation for this study in which it is emphasised that transitional PC is where trust and uncertainty are addressed, so this SLR seeks to outline how trust and uncertainty are important aspects of the PCT that still need attention in research. The relational dimension in PCT where stability is important is another area that has been included in this study in which the importance of the job security factor in the PC has been addressed to show how uncertainty is embedded in the PCT and its importance when studying the PC. Jepsen and Rodwell (2012) outlined categories of PCT where the balanced PC includes external employability where the focus is on the employers and organisations developing employees' employability within and outside of the organisation which will be a focus in this study. In the theory of the PC, as provided in the evaluation-based construct, the exchange relationship and the perceptions that employees might have regarding the reciprocal obligations of their employers is investigated (Tekleab et al., 2020). Perceptions of contracts among individuals involved in a social exchange relationship are commonly referred to as psychological contracts (Gilst et al., 2020). Therefore, the PC can be referred to as the perception of the reciprocity of the shared commitments of individuals involved in an exchange relationship. Odhiambo (2015) elaborated that the PC consists of the perceived obligations of both employers and employees. Odhiambo (2015) further cited Rao and Narayan (1998) in their definition of perception as the most important cognition factor that helps people make sense of their environment and as a determinant of human behaviour. Estreder et al (2018) highlighted that individual and shared perceptions should not be ignored when studying PCT because they both influence the effects on work-related outcomes. Previous systematic reviews and literature reviews have focused more on the overall psychological contract concept than on the perception of the psychological contract. The extent of fulfilment of the employers' obligations influences the employees' perceptions of the state of the PC, and it is necessary for both the employees' and employers' obligations to be clear and understood (Odhiambo, 2015). However, whilst the PC consists of both employers and employees perceived obligations, as mentioned above, it also refers to the perception held of the terms of the employment relationship, and failure to fulfil obligations and promises has been found to lead to unfavourable work and individual outcomes. The perceived terms of the exchange relationship that are largely unspoken are referred to as the PC. These might include, but are not limited to, opportunity for growth in respect, procedural fairness, or salary (Schalk & Soeters, 2008). Shen et al (2019) were of the opinion that the features of formalised contracts do not convey as much weight in the employment exchange relationship as the perceptions of the psychological contract (the context and norms relating to evaluation of the contract). contract as when employees and employers tacitly can differentiate and analyse amongst themselves and predict the expectations that they hold for each other without having to say anything to one another. Robinson et al (1994) and recently, Nizamani et al (2017) noted that in psychological contracts employees have beliefs that organisations will be able to pay them a reasonable wage, offer them job security and also growth within the organisation, as organisations will be rewarding their performance towards their job. Trust and uncertainty are part of PCT in the transitional dimension and they are an important part of the state of the PC, as elaborated above (Kutaula et al., 2020). Hornung and Rousseau (2017) found that it was necessary to consider perceived fairness and trust in the state of the PC jointly as they can predict individual, related outcomes such as PC violation. Clinton and Guest (2014) provided evidence that PC breach was linked to organisational fairness. As part of the state of the psychological contract, trust is an integral part of the concept as it influences the parties involved in keeping their promises and obligations. Braganza et al (2020) found a substantial positive relationship between the PC and trust. Braganza et al (2020) found that violations of the PC reduce the level of trust between employers and employees. In an earlier study, Gracia et al (2007) found that trust and fairness are dimensions of the state of the PC that influence prediction of fulfilment of the PC. The non-existence or the lack of fairness and trust might result in the mismatch of what was anticipated and what has been delivered and might give rise to feelings of anger (Estreder et al., 2018). Heyns and Rothmann (2015) found that if there is perceived trust followers were likely to respond and participate in trusting behaviours. Cullinane and Dundon (2006) regarded trust to be part of all psychological contracts on both a cognitive and affective basis, with cognitive trust being rooted in an exchange association and material gains, while affective trust is regarded as the respect given to the relational bonds of the employment relationship. Organisations must be aware of the foundation of trust that employees hold, enabling them to manage the employment relationship. A recent study by Lamertz and Bhave (2017) found the state of the PC can be affected when employees do not have high levels of trust in their organisations or employers to honour their promises and be fair. Feelings of betrayal, anger, or resentment might develop among employees when they perceive that an organisation or employer has failed to meet one or more of the PC's obligations that they expected to be met. Welander et al (2017) agreed that such feelings might then result in negative attitudes and behaviours towards the organisation. Armstrong and Taylor (2014) suggested that a psychological contract promises job security to employees. Ma et al (2019) defined job insecurity as a psychological state in which employees have different expectations regarding their employment continuity within organisations. Some scholars (Griep et al., 2016;Niesen et al., 2018) have defined job insecurity in quantitative terms (continuation of the job) and qualitative terms (essential characteristics of the job). Considering that violation of the PC has been found to have a negative impact on the employees' performance towards the organisation (Nizamani et al., 2017), then it is necessary to consider the impact that the violation of the PC might have on job security. Staufenbiel and Konig (2010) tested a model on job insecurity and its effects on several work attitudes and found that job insecurity leads to reduced work attitudes and behaviours.

Perceived Psychological Contract, Trust (State of the Psychological Contract) on Job Insecurity
Although the above has been accepted, the findings of an empirical study carried out by Tian (2009) supported the idea that job insecurity does, in some instances, effect positive behaviours and attitudes in employees. Employees might be motivated to become valuable to the organisation by working harder to obtain approval and acknowledgement from management and feel more secure about the future of their employment (Debus et al., 2019). Yang and Chao (2016) agreed with the study by Tian (2009) as they also found that employees who regard their PC to be fulfilled by their organisation perceive that they have more job security than employees who perceive their psychological contracts to have been violated or are not being honoured. Ma et al (2019) argued that job insecurity among employees leads to perceptions of violation of the PC and might result in counter-productive work behaviours. However, employers and organisations might not be able to fulfil the psychological contract because of limitations in the economy (Salladarre et al., 2011). Sanders and De Grip (2004) regarded the concept of employability to be embedded in the psychological and social constructs. Sanders and De Grip (2004) expressed that individuals' capability to adapt to suitable employment within shifting work environments contributes to being successful and satisfied with their careers. Recently, Yeves et al (2019) generalised employability as the capability of an individual to obtain employment and retain employment both at the organisational level and in the external labour market. Sok et al (2013) had earlier observed that employability is seen as the outcome of the interactions between employers and employees. Sok et al (2013) explained further that employability is enhanced when employers meet their obligations in providing opportunities for continuous training and development of their employees. In this environment, Sok et al (2013) have argued that employability can influence employees' behaviours and attitudes in learning and improving their employability in the organisation or outside the organisation. Vanhercke et al (2014) acknowledged that when employers meet their obligations in terms of the PC, it influences employees' perceptions towards their employability. Recently, Moreira et al (2020) has acknowledged that when defining employability the perception part of employability should not be left out as it has been found to positively be associated with the performance of the individual. The authors go on to say that when defining employability the perception ends with the individual on the way that they view their abilities to be able to maintain employment throughout their careers. Li et al (2016) acknowledged that the PC might be affected negatively when employees' performance management at work is not done effectively. It is necessary to address the PC of employees to see if any violation has occurred because this affects individuals' performance. When the PC is managed effectively, employers might gather the required information to plan ways to increase their employees' performance (Shen et al., 2019). Violation of the perceived PC has negative consequences and a decrease in psychological attachment and identification with the organisation might be presented by employees who feel the organisation's performance management is not fair (Yan et al., 2018). Liu et al (2020) found that both transactional and relational PC fulfilment had a direct effect on temporary workers' task performance and how they identified with the organisation. Liu et al (2020) found also that relational PC fulfilment had a stronger effect on long-serving employees than those that had been with a company for less than a year. Ruokolainen et al (2016) identified that different patterns of the PC related differently to the in-role performance over time. The aim of this article was synthesising research regarding the relationship between the PC and job insecurity and how these influence individual outcomes (individual performance and perceived employability) and work-related outcomes (PC and perceived psychological contract violation) as they emerge in the employment exchange relationship.

Research Method
To ensure that literature relevant to psychological contracts, job insecurity, trust, perception of the psychological contract, individual performance, and perceived employability were identified, a systematic literature review (SLR) was applied. A systematic approach was used to select, identify, and critically evaluate available research to clarify the aims of synthesising to address a clearly defined research question (Booth et al., 2016). The Preferred Reporting Items for Systematic Reviews and Meta-analysis (Page et al., 2021) was applied during this research to select the studies that were included in this literature review. A PRISMA is a statement based on evidence consisting of a set of items used in systematic reviews and meta-analyses (Page et al., 2021). The PRISMA flowchart was applied in this study to map the number of sources identified, included, and excluded and the reasons for both inclusion and exclusion. By applying the PRISMA in the systematic literature review, bias is minimised because there are formulated research questions and the PRISMA method is comprehensive in involving thorough criteria and instruments that screen out unrelated articles as well as being effective in abating biases.

Inclusion Criteria
Articles that were published in English, in peer-reviewed journals and available in full-text were included. Electronic searches were performed on databases that contain published studies about the perception of the psychological contract and trust (state of the PC), work outcomes (perception of the psychological contract and job insecurity) and individual outcomes (individual performance and perceived employability).

Exclusion Criteria
Unpublished theses and dissertations for the period under review in this study were not included in the articles for the analyses in the PRISMA. Also, articles that were published before 2009 were not included in the analyses and articles published after December 2020. The variables that were excluded included all that are not mentioned in the search process below, excluding other variables not mentioned below narrowed the search to articles that needed to be included in this study. Papers with participants that did not involve employees were excluded from this study. Other reasons for exclusion are mentioned in the adapted PRISMA flow diagram in Figure 1.

Search Process
The Electronic Data Search (EDS) of the Northwest University (NWU) Library was used, which consists of databases such as Google Scholar, Academia, EBSCOHOST, JSTOR, Emerald Insight Journals and Scopus among many others that the University subscribes to. The following search terms were used: "perceived psychological contract" OR "psychological contract" AND "trust" OR "state of the psychological contract" AND "perceived employment uncertainty" OR "job insecurity" AND "employability" AND "employee performance", for articles published from 2009 to 2020. Studies were analysed and coded by two authors and relevant information was included and tabulated in Table 1 according to the themes of the variables they were investigating. The search of the above databases was conducted using the keywords and their combinations related to the PC and different individual and work-related outcomes in various industries, as highlighted in Figure 1 below.

Results
The sources of the present study were reviewed based on a consensus decision to include 45 sources in the systematic literature review. The sources were read several times to capture  an overview of the content. The sources were tabulated according to author and year, the aim of the study, type of paper, sample, method and the primary outcomes of the studies. The search of the databases produced a total of 17 904 sources. After removing 12 921 duplicates, 905 sources remained, of which 769 sources were excluded for reasons 1, 2 and 3 because their focal points were irrelevant to this study. After this process had been completed, 136 sources remained, of which 45 were included in the systematic literature review. 91 of the remaining studies among other sources were included in the discussion of the SLR. The 45 selected sources included 38 empirical studies, and 7 literature reviews. All the studies selected were carried out with managers, employees, and supervisors. Participants in the studies were from different countries, including the USA, UK, China, India, South Africa, Nigeria and India. Table 1 on the next page shows a summary of the selected sources. Overall, the results highlight the importance of the PC in understanding the employment relationship. Future research directions are suggested and also the limitations of the study are discussed. The results of the study confirmed that perceived PCV explained the relationship between turnover intentions and exposure to bullying partially. It was also shown that employees who had high benevolence were more affected by bullying behaviour and the effects were detrimental to all employees exposed to workplace bullying.

Identification of studies via databases
The authors noted that their study could have been exposed to mono-method bias as only selfreported questions were applied in the study. 6 Flower et al (2015) Perceptions of fairness in the psychological contracts of allied health professionals.

31
Bargsted (2017). Impact of personal competencies and market value of type of occupation over objective employability and perceived career opportunities.  -Doleh and Hammou (2015) noted that perceptions held by employees regarding their PC being breached or violated might aggravate or alleviate the adverse effects on employees' individual and organisational outcomes that were studied. As mentioned earlier, the findings of Tekleab et al (2020) that perceptions that employees are bound to have regarding their PC are influenced by the reciprocal obligations of their employers in the employment relationship. In a study of government employees, Botha and Moalusi (2010) found that different values influence the perceptions of the employees' psychological contracts (PC). Botha and Moalusi (2010) found that lack of promotion and ill-treatment were the main issues that were influencing the perceptions of the PC. The findings concurred with those of Bordia et al (2010), who found that the PC should be regarded as an individual's perception. Similarly, Dadi (2012) noted that have failed to agree on one definition of the PC because of its embeddedness in perceptions and, based on findings that indicated that the PC can be influenced by different aspects including nationality, beliefs and culture of expectations or perceptions, proposed a definition that: "The psychological contract is a set of individual obligations or expectations unknown to the employer in respect of the exchange relations between the parties involved" (p. 98). Ahmed et al (2016); Pramudita and Sukoco (2018) found that perceptions of the PC are directly linked to the behaviours and attitudes of employees towards their organisations. Gilst (2020) believed that certain remedials could be applied when there are negative perceptions of the PC not being fulfilled, such as intra-organisational mobility to facilitate employability and employee development. Similarly, Gilst et al (2020) proposed that compensating inducements to remedy psychological contract breach could be an alternative way to alleviate negative perceptions of the PC using communication or job alternatives. Recent developments in research about the PC have strengthened the significance of understanding the concept and its application in understanding attitudes and behaviours of employees in different industries (Akkermans et al., 2019). Ghani et al (2020) found that perceived psychological contract breach (PCB) or violation influenced knowledge hiding by Chinese employees and abusive supervision, which was confirmed by Salin and Netelaers (2017), who found that perceived PCV or PCB explained the relationship between workplace bullying and high turnover rates. PCB was found to be associated with depression in the study by (Flower et al., 2015). Although employee well-being was not discussed in this study, this observation highlights the extent to which negative perceptions of the PC can affect employees' health. Salin and Netelaers (2017) investigated the relationship between exposure to workplace bullying and intentions of turnover and found that the relationship was mediated by the perceptions of the PC, and the benevolence of the employees acted as the moderator. Salin and Netelaers (2017) confirmed that perceived PCV explained the relationship between turnover intentions and exposure to bullying partially and that employees who had high benevolence were more affected by bullying behaviour and the effects were detrimental to all employees exposed to workplace bullying. After a systematic literature review, Kutaula et al (2020) highlighted the need to conduct PC studies in other cultures because they found a lack of studies in Asian literature. This finding provided the idea to apply the PC in the construction industry in South Africa. Bal et al (2010) investigated how social interactions altered the association that exists between psychological contract breach (PCB) and work performance and found a negative association between PCB and work performance and that social exchanges moderated this relationship. Employees who had high social exchange associations, alleged organisational support and trust, did not perceive the existence of PCB, and their performance was not affected. Alromaihi et al. (2017) stated that it is important that individual performance of each employee is understood so that informed management decisions can be made, as they are based on individual performance. Shen et al (2019) found that when employees perceived PCB, their performance was affected negatively. It was found that in-role performance was affected and that perceived procedural injustice also affected the performance of the employees. When the performance of employees is lacking, it has been found that it is expensive for organisations (Li et al., 2018). In their respective studies, Li et al (2018); Shen et al (2019) found that, when employees perceived PCB, they had a tendency not to share the responsibility for reaching the goals of the organisation, thereby affecting the overall performance of the organisation. Employees also reduced being humane and committed towards the organisation which can become expensive for the organisation if employees do not meet their profit-making goals. Liu et al. (2020) found that PC fulfilment contributed to employees' performance and it was relatable to previous studies in organisational behaviour. However, Liu et al (2020) expressed a strong opinion that the relational PC had greater influence on the performance of employees than other forms of the PC. Another important view, emerging from the present systematic literature review was the relationship between the PC and job insecurity. Niesen et al (2018) articulated that the PC promises job security to employees when they are of the belief that they will have their job for as long as they want it. Niesen et al (2018) examined the relationship between job insecurity and innovative work behaviour (IWB) and how PCB explains this relationship. It was found that PCB moderated the relationship between JI and IWB, which further supports the notion that, when employees can generate and implement ideas in their work, they are able to alleviate their perceptions of PCB. Koen et al (2019) believed that job insecurity prompted performance and investigated multi-level analyses on job insecurity. Koen et al (2019) found that job insecurity was positively linked to supervisor-rated performance and that employees devoted extra effort to their job performance when they felt that there was a great potential for job loss. Koen et al (2019) concluded that the motivation brought by job insecurity was more effective when both the employment and the employee were threatened with job loss. Jiang et al (2015) found a decrease in job insecurity when employees perceived that their PC had been violated. Ma et al (2019) found that PCB partially mediates the effects of job insecurity on CWB on both the organisational and interpersonal level and that these differ greatly for permanent and contract workers. This finding was supported by Yan et al (2018), who carried out a study focused on organisational commitment and organisational support and how these moderated relationships between PCB and work-related attitudes and behaviours of workers. Yan et al (2018) noted that the lack of support and trust in an organisation resulted in employees perceiving PCB which affected their behaviours and attitudes. This idea was supported by a study undertaken by Welander et al. (2017), in which it was found that turnover was high among social workers and who do not hesitate to quit their jobs when they have no support from their organisations and when they have perceived PCV. Jandaghi et al (2011) found that job security had other mitigating factors that also contributed to how the employees viewed their job security or insecurity. Costa and Neves (2017) investigated JI and how it affected individual outcomes and found that the PC moderated the negative relationship that exists between JI and individual outcomes that were increased by perceived PCB. Jiang and Lavaysse (2018) conducted a meta-analysis study in which they found that, as employees face the unavoidable essential alterations in the world of work, including less secure employment, JI is becoming one of the realities in the workplace. Jiang and Lavaysse (2018) suggested that organisations that are going through changes could help employees to cope with JI by involving their employees in decision-making regarding their jobs and fostering relationships between supervisors and their subordinates that encourage effective communication. Griep et al (2016) found that the anticipation of harm because of job insecurity also had an influence on the perception of losing the actual employment and the uncertainties that are brought by anticipation of loss of employment. Kwabiah et al (2016) investigated how three different industries (para-military, civic service, and the private sector) were affected by job insecurity. It was found that employees' satisfaction with their job and job security should be investigated by management so that organisational commitment and employee performance can be improved. Kwabiah et al (2016) highlighted the importance of the perception of job insecurity among employees in different industries and how this can affect their performance. It is noted that Kwabiah et al (2016) investigated three different industries and were able to make a conclusion that is applicable to those industries and can be generalised to the construction industry. The components investigated by Kwabiah et al (2016) can be applied to the construction industry, so that management can map policies and procedures that enhance performance in their employees. Staufenbiel et al (2010) investigated job insecurity and how it affects and influences in-role behaviour, organisational citizenship behaviour (OCB), turnover intention and absenteeism. When a PC is considered to have been violated, Biswas (2016) observed that the situation depicts perceptions of employees' evaluation of the abilities of their employers to fulfil exchanges related to work-related efforts. Biswas (2016) highlighted that PCV might occur unintentionally and might be moderated by a strong leadership exchange that might depict that the nature of the business PCV happens unintentionally. Dhurup et al (2015) found that, when PCV occurs, employees' feelings of insecurity within the organisation might occur and mistrust might also develop. In a study that was focused on sports coaches, Dhurup et al (2015) affirmed that, when PCV occurs where the mutual understanding was violated, the coaches wanted to leave their employers. Braganza et al (2020) found that trust in the job by employees has become highly significant in attaining positive organisational outcomes, and that trust prevents employees from breaching their contracts with the organisation. It was found also that sufficient job engagement enhances employees' trust based on their psychological contracts. Braganza et al (2020) emphasised that employers should be aware of the impact that the adoption of Artificial Intelligence has on PCs so that employees do not experience what they termed "alienational psychological contract". Jiang et al (2015) asserted that, when psychological contract breach (PCB) occurs, there are negative effects involved, yet, they also found that these negative effects can be moderated by the organisational context. Jiang et al (2015) specified that employees who feel higher PCB are those who experience it at individual level rather than in a group unit in the organisation that was not affected by organisational change, and they showed reduced job security and job satisfaction. Jiang et al (2015) highlighted that employees involved in organisations that were experiencing change experienced a high level of PCB on an individual level, or as a group unit if they were affected negatively by the change. Li et al (2018) found that the organisational context (environment in this case) influenced how employees reacted to their PC being violated or breached. It was found that perceived PCB significantly influenced working behaviours and how employees perceived their psychological contract. Li et al (2018) found that, if there was perceived mistrust and failure to deliver on promises, it resulted in higher intentions to quit the organisation. Two environments were differentiated to which employees in the study were exposed: the (very important persons) VIP room, and mass tables. The findings of the study confirmed what Jiang et al (2015) highlighted about the organisational context influencing PCB. Li et al (2018) found that, if employees who worked on the VIP tables experienced that the casino was unable to fulfil their promises and obligations or PCV, they were more likely to leave the organisation than those who worked on mass tables. Welander et al (2017) found that PCV occurred among social workers who were interviewed during a study. It was found that the PCV that the social workers felt they experienced was attributed to the employment relationship exchanges that did not happen according to what they were promised or were obligated to have happened because of the employment relationship. The interviews that were held with the social workers revealed that the mistrust that developed was a clear expression of a violation of the obligations and expectations that existed in the employment relationship. Flower et al (2015) also suggested that the PCV occurred because there were disturbances in the exchange relationship found between employees and organisations. Flower et al (2015) observed that Social Exchange Theory might not be fulfilled by both parties, hence the party that is affected will try to retaliate to bring balance to the employment relationship. Yan et al (2018) concluded that, when violation occurs on a PC, various work-related behaviours are affected as a result of organisational commitment being affected. It was found also that organisational commitment played a moderating role when PCV occurred. Having considered the impact of the PCV, it could be concluded that investigating the link between the PC and employability to determine how the PC impacts employability is important in order to establish what happens when there is perception of the PC being violated or breached. Researchers have found that when PCV occurs, employees might develop intentions to leave their organisations which influence their perceptions of employability outside the organisation (Philippaers et al., 2016;Sok et al., 2013;Vanhercke et al., 2014). Bargsted (2017) found that perceived employability of employees might be influenced and affected by the economy of market that is available to the employee. Bargsted (2017) explained further that the availability of jobs in the market and the need for the skills that the employee has determines their employability in the market economy. Sok et al (2013) argued that the PC plays an important role in influencing employees' perceptions of employability. Based on their study, Sok et al (2013) found that, if employees valued their PC more positively, they responded with positive behaviours and perceptions of their employability. Forrier et al (2015) found that all three concepts of employability (job transitions, perceived employability and movement capital) all contribute to how individuals interpret their employability both in the internal and external environments. The findings of the study by Forrier et al (2015) revealed that practices initiated by employers in maintaining their obligations have a bearing on attitudes, intents, and actions of employees, as well as the effect of Social Exchange Theory, in the employment relationship. In an earlier study, Aggarwal and Bhargava (2009) found that training and development are important to facilitate employability in employees. Aggarwal and Bhargava (2009) acknowledge further that training and development have become an important part of employees' PC and, when employees perceive that training and development has not been facilitated by their employers, they might experience a violation of the PC. Vanhercke et al (2014) found that perceived employability has many facets and having studied the psychological part of employability, they found that perceived employability (psychological notions) is not the same for all individuals. Vanhercke et al (2014) noted that, although perceived employability is treated the same in literature, it is influenced by the capabilities and dispositions of individuals. Bargsted et al (2021) suggested that, although perceptions are individualised, employees who are highly skilled and are motivated by their environments and employers to advance themselves continuously, have positive perceptions about their employability opportunities. Philippaers et al (2016) were of the view that perceived employability decreases affective commitment, which they found also had a negative impact on job performance. Dries et al. (2014) found that employees who have lower perceived employability invest in their existing employment relationships and maintain long-term commitment more than those who have higher perceived employability, as the employment relationship for the parties involved is embedded in Social Exchange Theory. Philippaers et al (2016) agree with these findings as they found that employees who have higher perceived employability are focused on maintaining their employability outside the organisation rather than maintaining loyalty to the organisation. Philippaers et al (2016) elaborate further that employees who are highly employable are likely to become frustrated when their expectations are not fulfilled by their employers. Unfulfilled promises might become detrimental to employees' performance as they focus on aligning their employability with other organisations that will hire them and offer career progression that matches their potential (De Cuyper et al., 2011). As discussed above, when employees perceive that their expectations of continuous training and development to enhance their employability are not being met, their individual performance might be affected. Therefore, it is important to consider individual performance and how it is affected by PC. Based on services sector research, Bal et al (2010) found that there was a undesirable relationship between PCV and individual performance, but they found also that social exchanges in the employment relationship moderated the effects. Bal et al. (2010) found that trust impacted on the PCV and explained that, based on their study, they concluded that individual performance was lower in employees who had lower social exchanges in the organisation. This was not affected by the level of the PCB. Bal et al (2010) explained further that employees who had higher social exchanges in the organisation produced higher individual performance, which decreased when their perceived PCB was higher.  supported this idea and observed further that individual performance suffered or decreased when employees perceived that their PC had been violated or breached.  also found the PC to be an important mediator in the employment relationship and individual performance. Kwabiah et al (2016) noted further that effectively managed psychological contracts resulted in increased individual performance. Researchers have shown that, when the PC is violated, employees will have decreased individual performance and high levels of turnover (Bal et al., 2010;Kwabiah et al., 2016;Li et al., 2016). In a study of migrant Chinese construction workers, Li et al (2015) found that the fulfilment of the PC had an influence on job involvement and job performance and that there was a relationship between the PC and labour contracts. Li et al (2015) acknowledged that there were previous studies that had shown that there is a positive association between PC fulfilment and job performance, but they found that there was a link between the migrants' perception of PC fulfilment and job performance, moderated by job involvement. Li et al (2015) found also that, in the absence of a labour contract, the employment relationship was enabled by high-quality social exchange between the employers and the migrant workers, which confirmed the positive influence of the PC on job performance. Li et al. (2016) were of the opinion that fulfilment of the PC re-assures trust and offers mutual benefits in the employment relationship. However, when employees perceive that they have not been receiving the benefits of the employment relationship, they might retaliate negatively. In existing literature, a breach of the PC has been linked with behavioural reactions, including PCV (Biswas, 2016;Dhurup et al., 2015), job insecurity (Ma et al., 2019;Niesen et al., 2018;Staufenbiel et al., 2010), and employability (Sok et al., 2013); Vanhercke et al., 2014;Philippaers et al., 2016). The constructs mentioned above have also been linked with having an impact on individual performance (Bal et al., 2010;Kwabiah et al., 2016;Li et al., 2016). Ruokolainen et al. (2016) reported that employees with perceptions of balanced obligations between them and their employers showed higher individual performance on their tasks, while employees who perceived that their PC has been violated showed lower individual performance. Furthermore, Shen et al (2019) found that, when a PC has been violated or breached, this strongly influences in-role performance which ultimately has an impact on the performance of the organisation. Lee et al (2014) argued that, when employees perceive that they are not receiving adequate organisational support to complete their tasks, their performance is affected, which was also found to be damaging to the organisation's overall performance. Yang and Chao (2016) suggested that employers should have employment practices that promote positive employee perceptions of organisational support. Philippaers et al. (2016) investigated further how performance is affected by perceived employability and found that employees who had lower perceived employability had reduced affective commitment over time, and affective commitment is an essential factor for individual performance.

Conclusion
Based on the PRISMA methodology to analyse and critically evaluate existing literature, the findings of this study contribute significantly to the present body of knowledge about the PC, with a special focus on how the PC and job insecurity (JI) influence individual outcomes (performance and perceived employability) and work-related outcomes (PCV). By applying the PRISMA, as prescribed and endorsed by Page et al (2021), to existing literature, it was found that the PC has strong relations with several different outcomes. In this systematic literature review, studies about the PC and job insecurity, trust, PCV, employability and individual performance have been aggregated. It has been highlighted in the study that employers and organisations should not be caught up in making unrealistic promises they might be unable to fulfil. Promises made and not fulfilled might cause employees to perceive violation of their PC and the parties involved in the employment relationship might suffer. In this article, it has been shown clearly that a PC that is perceived to have been violated might cause different outcomes and might have negative consequences for those involved in the mutual relationship. Therefore, it is necessary for both employers and employees to see and understand why some of the promises might be met for reasons beyond each other's control. It was also noted in this study that organisations and employers should identify and recognise variances in behaviours of their employees and use mechanisms, such as surveys, to determine the root causes of those variances. The present study has offered a research avenue that can enable researchers to further understand the outcomes of the PC both at the individual and work-related outcomes. With the variables discussed in this study, it has been evident that individual outcomes (individual performance and perceived employability) can have two dimensions in being positive or negative depending on the perception of the individual employee involved. Of the workrelated outcomes (psychological contract violation) that the study focused on may lead to counter-work productive behaviours.

Theoretical and Practical Implications
The study has aggregated studies that show that the effective management and the understanding of the PC can prevent destructive behaviours by employees, managers and employers should be attentive to employees' perceptions of the psychological contract. The article has also created awareness that understanding employees' perceptions of their PC fulfilment or violation has a major influence on the quality of their employment relationship, highlighting the importance of the Social Exchange Theory in the effective management of the employment relationship. It is recommended that everyone who is involved in an employment relationship should identify and recognise mutual obligations so that, if there is any breach (actual or perceived), it can be addressed by both parties. The study has revealed the broad theoretical and experimental evidence that supports the importance of understanding the PC in employment relationships, as shown in Table 1 above. Jiang et al (2020) in their analysis of the PC in construction management found that there are limited studies that apply the PC in construction management. Nine papers that were published about the PC in construction management were identified, which highlights that PC studies in the construction industry are lagging behind. The above finding points the need for research of the PC in the construction industry. The study has shown that it is important that employers are able to identify and understand behaviours that are associated with how employees respond to, and cope with, the threat to their perceptions of their psychological contracts. The study sought to establish the relationship that the PC has on different work and individual outcomes, and it has highlighted that perceived psychological contracts have a huge impact on employees' behaviour both at an individual and organisational level. By providing specific individual and work-related outcomes in which employees perceive their own promises and their individual evaluation of the obligations and promises of their employers the findings of this study have contributed to the literature about the PCT. A wide array of studies about the psychological contract (PC) has provided information for both employees and employers as they engage at work. However, a better understanding of the contributions and appropriate assessment was needed. From a practical viewpoint, the findings of this systematic literature review have shown the importance of organisations and employers implementing surveys in their organisations periodically. Implementing mechanisms such as surveys will also help organisations in the construction industry to gather the thoughts of employees regarding their employment relationships and direct the appropriate people address a situation that could be arising if any is identified. The process above might lead organisations to implement counselling programmes to mitigate the consequences of detrimental behaviours to the organisation. Surveys can also be used to help organisations to assess the needs of their employees and then plan ways and interventions to manage situations that might arise. By being able to assess the needs of their employees, organisations might be able to alleviate situations in which negative work outcomes are inevitable. Mutual trust should exist in the employment relationship to facilitate fulfilment of the PC, which encourages job performance. The importance of psychological contracts for organisations and their effects on employees' behaviours has been shown in this systematic review. It has been shown in this study that it is beneficial for employers and organisations to manage their employees' PC effectively to eliminate counter-productive behaviours.

Limitations and Recommendations for Future Research
The systematic literature review was focused on articles about PC and different outcomes. The SLR was focused on the PC, trust, and job insecurity and how these influence individual outcomes (individual performance and perceived employability) and work-related outcomes (PC and perceived psychological contract violation). The constructs studied can be said to be not exhaustive of all the outcomes that can be influenced by the PC. However, this made the amount of data collected manageable. The study also did not focus on the statistical significance of all the articles included in the SLR as this was not the focus of the study but the outcomes of the studies and how the PC has been applied. Future researchers are encouraged to investigate the definitions of the PC throughout the decade. Researchers in future might carry out a comparable study of the influence of PC using quantitative methods in self-reported questionnaires and also in qualitative studies using focus, groups for example. Future researchers might also investigate the different dimensions of the PC and their influence on individual perceptions of the PC. Future studies might also look into the PC before the Covid-19 pandemic and post the pandemic and how the perceptions of the PC have shifted because of the pandemic.