Half Just or Half Unjust? the Influence of Dispositional Optimism on the Link Between Interpersonal Peer Injustice,Negative Emotions and Sleep Problems

Abstract

While optimism – a cognitive disposition that involves positive beliefs about the future – is a strong predictor of wellbeing at work, we know little about its role in how people experience and respond to injustice at work. In other words, does optimism mitigate or exacerbate the experience of workplace injustice? This is an important practical question because optimism is a promising avenue for interventions. Taking an affective events perspective, we expect that daily events of peer injustice trigger affective reactions, and that the degree of trait optimism will influence the strength of these affective reactions. Thus, we develop two competing predictions. The reverse buffer hypothesis, which suggests that optimists’ heightened expectations lead to increased disappointment and hence more negative emotions in the face of injustice, and the buffer hypothesis, which suggests that optimists’ better use of coping strategies allows them to experience less negative emotions. In a 10-day diary study with 251 employees, we find support for the buffer hypothesis of optimism on peer injustice experiences: those higher in optimism reported fewer negative emotions and lower levels of sleep problems the night following such experiences. Our findings illustrate how cognitive and emotional mechanisms interact in predicting reactions to injustice, particularly sleep problems.

Keywords

peer justice dispositional optimism sleep affective events

Introduction

Interpersonal mistreatment in the workplace is common in organizations and takes a toll on the wellbeing of individuals (for a review, see Dhanani & LaPalme, 2019). These effects often ripple through organizations, as victims of mistreatment may translate their suffering into mistreatment responses, leading to a spiral and culture of mistreatment among coworkers (Vranjes et al., 2022, 2023). It is therefore important to understand the causes and the moderators of the experience of mistreatment, with the goal of developing interventions at the organizational, group, and individual levels of analysis.

In this paper, we focus on daily experiences of injustice amongst peers, which are typical manifestations of mistreatment. A peer’s communication, action, or non-action is perceived as an interpersonal injustice when comparing negatively to one’s normative expectations of peer treatment, such as politeness and respect (Cropanzano et al., 2015). As people tend to have more work interactions with their colleagues than supervisors, there are typically daily opportunities for interpersonal injustice among peers in organizational contexts. This is important because injustice perceptions have been found to predict numerous important performance-related (Colquitt et al., 2013), employee wellbeing, and health outcomes (Manville et al., 2016; Rineer et al., 2017; Robbins et al., 2012).

How individuals react to experiences of injustice may also depend on their beliefs about the future. Fairness heuristic theory (Van den Bos, 2001), which has received empirical support in numerous studies, suggests that a central reason why people care about justice is that it helps them manage uncertainty and protect themselves from exploitation (Lind, 2001). In addition, people with lower trust propensity and higher risk aversion react more strongly to interpersonal justice experiences (Colquitt et al., 2006). These studies suggest that a disposition toward negative expectations about the future may lead to stronger effects of perceived injustice. Surprisingly, and to the best of our knowledge, no studies have examined the effect of a tendency to expect positive experiences at work. According to Alarcon et al.’s (2013) research, both optimism and hope encompass positive expectations at work. The narrower concept of hope revolves around the proactive steps individuals can personally take to shape a prosperous future for themselves, as Gallagher and Lopez (2009) point out. Conversely, optimists believe that their future success is influenced by a broader range of factors, including their own actions, the actions of others, or even luck. Optimism is a cognitive disposition that involves positive beliefs about the future (Carver & Scheier, 2014), and has been shown to be a strong predictor of various wellbeing outcomes. Our study focuses on optimism in relation to daily experiences of injustice.

Interestingly, the more positive expectations associated with optimism may not simply have the reverse effect or represent the opposite of what has been found for negative expectations. In fact, the optimism literature suggests that two competing effects are possible. On the one hand, optimism raises expectations, which then tend to lead to increased disappointment in the face of negative events (Britton et al., 2012). In other words, optimists may have more positive counterfactuals in mind to compare their actual experience to, and as fairness theory (Folger & Cropanzano, 2001) posits, the increased gap would then result in more negative emotional reactions and affect. This mechanism is also described as “the higher they are, the harder they fall” (Brockner et al., 1992). In the optimism literature, this potential amplifying effect of optimism on negative experiences is described as the “reverse buffer hypothesis” (e.g., Hochwarter & Thompson, 2010).

On the other hand, optimists typically use better coping strategies (Nes & Segerstrom, 2006), and may thus be better able to deal with adversities in daily life, an effect called the “buffer hypothesis”. In support of the buffer hypothesis, we might expect optimists to engage in various motivated justice reasoning strategies (Barclay et al., 2017) to maintain their positive beliefs about the future, even in the face of negative events.

In the present research, we aim to shed light on the role of positive expectations generated by optimism in the face of injustice experiences. Specifically, we examine the role of optimism in how people experience and react to daily peer injustices. Taking an affective events perspective on such experiences, we expect that daily peer injustice events will trigger negative affect, understood as a general distress that encompasses a variety of negative states. In turn, negative affect may worsen sleep quality the night after the event. Therefore, we test the opposing predictions from the optimism literature – the reverse-buffer and the buffer hypotheses – using a 10-day diary study with 251 employees. Understanding whether optimism mitigates or exacerbates the daily effects of injustice is practically important because optimism is a particularly promising avenue for intervention (Carver et al., 2010). Indeed, a large body of research shows that simple interventions, such as a mindfulness-based programs or the Best Possible Self intervention, can increase optimism in a matter of weeks (Loveday et al., 2018; Malouff & Schutte, 2017).

In the present study, we measure sleep quality on the night following the injustice event to illustrate the downstream effects of peer injustice, optimism, and affect. While the literature suggests a variety of wellbeing and performance-related downstream effects of (in)justice (for reviews, see e.g., Colquitt et al., 2001; Cachon-Alonso & Elovainio, 2022), we focus on sleep due to its high relevance to both wellbeing and performance (Barnes, 2012). Importantly, this design allows us to test the moderating role of dispositional optimism on daily experiences, whereas previous tests in the optimism literature focus on explaining the moderating role of optimism on between-person effects (e.g., Britton et al., 2012; Hochwarter & Thompson, 2010). Demonstrating within-person effects of optimism is more directly relevant to planning organizational interventions based on optimism that rely on the same person changing their level of optimism over time. In the following, we introduce the core elements of the justice and affective events framework that we draw upon before developing the two competing predictions that we then test.

Interpersonal Peer Justice Experiences at Work

Hundreds of studies of organizational justice demonstrate the benefits of justice and fairness sentiments for organizations and their employees (for meta-analytic reviews, see Colquitt et al., 2013). While previous research often used the terms justice and fairness interchangeably, Goldman and Cropanzano (2015, p. 313) argue that “‘justice’ should refer to whether one adheres to certain rules or standards, while ‘fairness’ should refer to how one responds to perceptions of these rules (and rule compliance).” In other words, justice judgments are more directly related to specific transgressions of “justice rules” (for a review, see Cropanzano et al., 2015), while fairness judgments are downstream judgments that can be influenced by a broader range of factors. Overall, both justice and fairness are typically divided into four dimensions: interpersonal (related to interpersonal treatment), informational (related to information provision), procedural (related to the processes used to make decisions), and distributive (related to outcome distributions). In the present work, our focus is on how people react when interpersonal justice rules are broken, that is, the interpersonal justice dimension. Indeed, on a day-to-day basis, interactional justice, which refers to the perceived fairness of personal treatment, is probably the more commonly experienced dimension of peer fairness. As Scott et al. (2007) point out, procedural and distributive justice are limited to situations of resource exchange, which occur less frequently. Interpersonal justice, on the other hand, can be felt in almost all interactions between coworkers, whether or not they involve resource allocation decisions. In the same vein, Loi et al. (2009) see distributive and procedural justice as structural forms of justice that tend to be stable over time compared to interpersonal justice, which is influenced by social factors that can vary according to individuals’ day-to-day experiences in the workplace. Furthermore, interactional justice treatment lies more within the discretion of employees, as they can decide how to communicate with their coworkers in any daily interaction. Coworkers do not always have the opportunity to decide on the allocation of resources or the decision-making process within their team or organization. Taken together, we focus on the interpersonal form of justice due to its greater significance in everyday interactions with peers compared to the other justice dimensions.

Interpersonal justice is typically conceptualized around the justice rules of dignity, respect, and propriety at work (Bies & Moag, 1986; Wang et al., 2019). An interpersonal injustice event, such as an insulting remark or unfriendly address, can be more easily attributed to a specific “guilty party” than organizational processes or outcomes, which often involve multiple parties and greater complexity (Folger & Cropanzano, 2001). This may be why interpersonal injustice is also particularly strongly associated with “hot” emotions, such as moral anger (O’Reilly et al., 2016), which are important affective experiences at work. Indeed, several studies within the so-called affective events paradigm (Weiss & Beal, 2005) have been conducted in the area of organizational justice, supporting the notion that daily experiences of injustice translate into affective reactions that then explain the downstream consequences and reactions at work (Weiss & Cropanzano, 1996). Furthermore, affective events theory suggests that situational and dispositional causes interact, making many of the fluctuating affective patterns that influence workplace behaviors and attitudes predictable (Weiss & Cropanzano, 1996).

Interpersonal experiences of workplace justice have multiple sources (Frazier et al., 2010). While most studies consider supervisors or organizations as the perpetrators of injustice, employees’ interactions with clients or coworkers are other important sources of interpersonal justice or injustice (Cropanzano et al., 2011; Molina et al., 2017; Skarlicki et al., 2016). Indeed, several recent studies show that coworkers are an important source of justice (Bensemmane et al., 2018; Fortin et al., 2019; Harris et al., 2020; Ohana, 2016; Ohana & Stinglhamber, 2019). In modern workplaces, where teamwork is often the norm and structures are less hierarchical (Cross et al., 2016), the interactions with peers tend to dominate daily experiences rather than those with managers. Thus, our focus is on daily interpersonal justice from peers or coworkers, which we refer to as interpersonal peer justice, defined as the extent to which an employee is treated with dignity, respect, and propriety by coworkers on a daily basis at work. Given that peers have no formal authority over other employees, unlike other sources such as the organization and supervisors, it is possible that the outcomes and mechanisms found for organizational and supervisor justice differ from those for peer justice. More research is needed to draw definitive conclusions on this aspect (Harris et al., 2020).

Injustice Experiences Trigger Emotional Reactions

Work events, such as unfairness experiences, trigger emotional reactions that lead to downstream attitudinal and behavioral outcomes. This core principle of affective events theory (Weiss & Cropanzano, 1996) implies a temporal dynamic. Indeed, the quality of workplace events can fluctuate, even within the same workplace relationship. For example, on Monday, your colleague might make a remark that seems inappropriate and therefore interpersonally unjust, while on Tuesday, the same colleague might be exceptionally polite (and therefore interpersonally just). As daily experiences change, emotional reactions follow and fluctuate.

The affective events paradigm (Weiss & Cropanzano, 1996) builds on the insights of appraisal theory, which posits that individuals evaluate each situation along various dimensions (Lazarus, 1991) in terms of valence and relevance to salient goals, in turn leading to an emotion (Barclay & Kiefer, 2017). Experiences of injustice are typically experienced as negative events that affect moral, group-standing, and instrumental goals (Cropanzano et al., 2001). Therefore, when people feel unfairly treated, they typically experience negative emotions. Empirical studies confirm that (in)justice perceptions are an antecedent of negative emotions at work (Barclay & Kiefer, 2017). Colquitt et al.’s (2013) meta-analysis confirms the association between interpersonal justice and negative affect for both event and entity justice judgments, and for both organizational and supervisor sources. It is also the only effect that significantly differs between these sources, highlighting the need to examine interpersonal peer justice dynamics as an additional important source of interpersonal (in)justice.

While affective events theory focuses on emotional reactions, we know that cognitions also play a central role in justice processes. Integrating trait optimism and personal dispositions related to cognitive style with affective events theory allows us to conceptualize and examine how cognitive and affective processes interact. Specifically, we argue that optimism moderates the daily relationship between injustice events and affect. In sum, our theoretical framework is situated within the affective events paradigm, which suggests that personal disposition, as a between-person variable, influences the event-affect relationship, a within-person effect.

The Moderating Role of Optimism

A central challenge for predicting and managing justice situations is that people react differently to similar justice situations (Colquitt et al., 2006). We argue that dispositional optimism help us understand such differences in reaction. Optimism is described as a “powerful cognitive filter” that can “alter individuals’ perceptions of the world and affect how they react and adapt to new situations” (Forgeard & Seligman, 2012, p. 108). In the present research, we focus on dispositional optimism, which is defined as “an individual difference variable that reflects the extent to which people hold generalized favorable expectancies for their future” (Carver et al., 2010, p. 879). Although dispositional optimism is a relatively stable trait, it is a thinking style that can be changed easier than other types of personality traits, and interventions to increase optimism have been developed and shown to be successful (Carver et al., 2010).

In the context of workplace injustice events, optimism is likely to be an important trait because it relates to how people interpret and cope with negative events (Nes & Segerstrom, 2006). Forgeard and Seligman (2012) argue that optimists are not more likely to deny problems, but their reactions to events differ from those of pessimists. Furthermore, optimism has important effects on health and wellbeing in general (Heinitz et al., 2018). Based on the optimism and organizational justice literature, we develop two alternative predictions and consider them in turn: the reverse buffering effect and the buffering effect of optimism on the impact of daily injustice experiences.

The Reverse Buffering Effect of Optimism

Optimists tend to expect good experiences. When their positive expectations are disconfirmed, the resulting disappointment can lead optimists to react more negatively than pessimists who are not surprised by bad experiences (Hochwarter & Thompson, 2010; Tennen & Affleck, 1987). Indeed, one of the seminal theories of justice reasoning, namely, fairness theory (Folger & Cropanzano, 2001), explain this effect in the context of justice judgments at work: justice judgments are based on counterfactual thinking. In determining whether a particular treatment is unfair, people ask themselves whether the situation would have been fairer had the potential perpetrator of injustice acted differently, whether the potential perpetrator could have acted differently, and whether they should have acted differently. In other words, injustice judgments result from a comparison of the event with hypothetical counterfactuals. The counterfactuals represent expectations: what treatment can and should be expected in the workplace? The higher the expectations and standards for just treatment, the greater the potential for a gap resulting from counterfactual comparisons. The cognitive disposition to expect positive treatment and events therefore translate into a more negative appraisal of an event as well as more negative emotional reactions.

In support of this perspective, research shows that optimists exhibit a higher level of negative affect when confronted with a stressor (Chang & Sanna, 2003). This logic also applies to interpersonal injustice experiences at work. As Britton et al. (2012, p. 713) note, “A negative interpersonal event challenges an optimist’s beliefs that they are likely to encounter positive outcomes, which could lead to heightened negative reactions.”

There is an additional reason to think that more optimistic people react to peer injustice with stronger negative emotions. Research suggests that optimistic people value interpersonal relationships more strongly than less optimistic people (Castellani et al., 2016). Fairness is an important signal of acceptance and standing within a group (Cropanzano et al., 2001), while unfair treatment signals low status. It is thus likely that optimists who are treated unfairly experience higher levels of goal frustration than less optimistic people. Greater goal frustration leads to more negative appraisals and therefore more negative emotional reactions. We thus posit:

Hypothesis 1a:

(reverse buffer hypothesis) Dispositional optimism moderates the negative daily coworker interpersonal justice-daily negative affect relationship such that the relationship is stronger for those higher (versus lower) on dispositional optimism.

The Buffering Effect of Optimism

Alternatively, one might expect optimistic individuals to have lower negative emotions when experiencing injustice from their peers. People are not only passive recipients of just or unjust treatment, but also active processors of justice-relevant information, and thus how they construe and interpret an event in the context of their own motives and goals is important (Barclay et al., 2017). People’s justice reasoning is motivated, and as optimists are motivated to uphold their beliefs in a better future, they are likely to adapt their perceptions and interpretations of injustice events accordingly. For example, due to their positive future outlook, optimists are more likely to interpret events as helpful than as detrimental (Weber et al., 2007). They are more likely to believe that a stressful present can change into a better future (Carver & Scheier, 2014). In addition, optimists dwell less on the negative aspects of their experiences and may even find benefits in stressful circumstances (Affleck & Tennen, 1996). Thus, they may be less emotionally affected by injustice events.

In addition, optimists are more likely to respond with positive coping strategies, including reducing and managing emotions (Nes & Segerstrom, 2006), focusing more on approach than avoidance. Approach coping tends to cause less negative affect than avoidance coping strategies (Ben-Zur, 2009).

In summary, there are arguments to expect that optimists are less negative in their interpretation of daily injustice workplace events and more successful in managing their emotions in the face of such experiences. Therefore:

Hypothesis 1b:

(buffer hypothesis) Dispositional optimism moderates the negative daily interpersonal peer justice-daily negative affect relationship such that this relationship is stronger for those lower than for those higher in dispositional optimism.

Downstream Consequences of Interpersonal Peer Justice Experiences on Sleep

To highlight the practical relevance of our research, we include a critical wellbeing variable: sleep. Sleep is a dominant activity in the lives of individuals. Despite its neglect in human resource studies (Barnes, 2012), sleep deserves attention because poor sleep is associated with numerous negative workplace outcomes, such as reduced job satisfaction (Scott & Judge, 2006), unethical behavior (Barnes et al., 2011), workplace deviance (Christian & Ellis, 2011), and team conflict (Barnes & Hollenbeck, 2009).

Several studies suggest that organizational justice predicts sleep quality and quantity (e.g., Kim et al., 2011; Manville et al., 2016). However, several questions remain about this relationship. First, while previous studies consider sleep as a mediator between organizational justice and health outcomes, little is known about the underlying mechanisms linking justice and sleep (for an exception, see Hietapakka et al., 2013, who consider job involvement and psychological distress as mediators). Second, not all studies find clear links between justice and sleep. For example, Eriksen et al. (2008) find no clear evidence of an association between a general measure of supervisor fairness and poor sleep in a sample of 4771 Norwegian nurses. Finally, there is a lack of evidence regarding the effects on sleep of injustice emanating from peers, a source of justice without authority over the recipient. Further research on the peer justice-sleep relationship and its underlying mechanisms appear necessary.

Within our paradigm of studying daily injustice experiences as affective events, negative affect is expected to mediate the justice-sleep relationship. Indeed, we have argued above that peer injustice is related to negative affect, which in turn has been shown to be a strong predictor of sleep problems. First, from a physiological perspective, negative affect leads to hyperarousal, resulting in increased difficulty in initiating and maintaining sleep (Slavish et al., 2018; Winzeler et al., 2014). Second, from a psychological perspective, negative affect is characterized by dissatisfaction and leads to stress and anxiety, and is therefore associated with sleep problems (Norlander et al., 2005). Litwiller et al.’s (2017) recent meta-analysis of sleep and work found a correlation of −.30 and −.17 between trait negative affect and sleep quality and quantity, respectively. The relationship between negative affect, sleep quality, and difficulty falling asleep is also found in daily studies (Slavish et al., 2018). Several negative emotions, including sadness, regret, shame, guilt, and loneliness (for a review, see Kahn et al., 2013), are linked to sleep problems, although much of this evidence is correlational. The results of previous studies on negative events and sleep problems at the daily level are somewhat mixed (for a review, see Sin et al., 2017), suggesting the need for further investigation. In this study, we examine how daily negative emotions related to daily peer justice experiences affect sleep. Therefore, we propose:

Hypothesis 2:

The daily negative emotions related to daily interpersonal peer justice are related to daily sleep problems, such that daily negative affect mediates the effect between peer injustice and sleep problems.

To test our hypotheses, we conducted a daily diary study with working adults, which allowed us to test the within-person main effects as well as the role of optimism as a between-person moderator.

Methods

Participants and Procedures

We administered a quantitative web-based survey to a sample of 300 employees from an online panel (Qualtrics) working in various US companies. The sample included 184 women (61.3%) and 116 men (38.7%), with a mean age of 45.6 (SD = 11.3), ranging from 23 to 70 years. On average, participants had worked in their current organization for 11.3 years (SD = 9), 26.7% have at least a master’s degree, 12.7% a high school degree, and 26.3% work for a company with more than 5000 employees. Finally, the three main represented sectors of activity are finance (18.7%), healthcare (18.3%), and education (18%).

The participants were invited by email and completed a prescreen inventory to ensure that they regularly interacted with coworkers. The main data collection took place in two consecutive weeks. On the first Monday, participants completed a general survey measuring dispositional optimism. Then, over the following nine working days (from Tuesday to Friday of the first week and from Monday to Friday of the second week), participants completed the daily diary questionnaire at the end of each working day. To encourage daily participation, e-gift cards were offered based on the number of questionnaires completed. Forty-nine individuals responded only to the baseline questionnaire and did not take part in any diary study. Therefore, they were excluded from the analyses, resulting in a final sample of 251 workers. We obtained 1778 data points from these 251 participants, representing a response rate of 59%. We performed an attrition analysis to examine differences between those employees who participated in the diary surveys (N = 251) and those who participated in the baseline questionnaire only and were therefore removed from our final sample (N = 49). We found no significant differences in optimism, gender, tenure, or size of the organization between these two groups of participants. Those who continued to participate in the diary surveys were slightly younger (44.9 vs. 49.1, p < .01) and more educated (2.9 vs. 2.4, p < .01).

Measures

Given that justice and negative affect (Wang et al., 2019) occur on a daily basis, we expect nightly sleep to be determined by changes in daily experiences. This daily approach is particularly well suited to test affective events theory, which posits that discrete workplace events cause discontinuities in employees’ affective state (Dalal et al., 2020). In this way, we align the theory and method by adopting a daily approach to test our model and measure our variable at the daily level. Therefore, we adapted the timeframe of the measurement instruments used, such that the items refer specifically to the day level (Ohly et al., 2010; see e.g. Koopman et al., 2020). All statements were evaluated on a 5-point scale ranging from 1 (strongly disagree) to 5 (strongly agree).

Interpersonal peer justice is measured using the Colquitt (2001) 4-item scale applied to coworkers. A sample item is “Today, my work group member treated me with respect.” Average Cronbach’s alpha over the 8 days = .88.

Negative affect is measured using the Watson et al. (1988) 10-item scale. Individuals were asked to report how they generally felt that day by responding to prompts such as “distressed” and “scared’. Average Cronbach’s alpha over the 8 days = .93.

Trait (dispositional) optimism is measured once in the general questionnaire on the first day using the 6-item optimism scale from the Life Orientation Test-Revised (LOT-R) developed by Scheier et al. (1994). A sample item is “In uncertain times, I usually expect the best.” Cronbach’s alpha = .82.

Daily sleep problems is measured using a 3-item scale derived from the sleep quality index of Urponen et al. (1991). “I woke up too early this morning” is a sample item. According to our theorizing that injustice experiences lead to sleep problems, these would only occur at night after such experiences. We therefore consider the measure of sleep problems taken the next day following the measurement of daily interpersonal peer justice and daily negative affect. Average Cronbach’s alpha over the 8 days = .65.

Control variables. We included in our initial questionnaire several potentially relevant demographic control variables, including age and gender. Previous empirical research suggests a relationship between age (Knudsen et al., 2007), gender (Reyner & Horne, 1995), and sleep. The relationship between age and sleep exists because of the poorer health of older people, which affects their sleep quality (Reyner & Horne, 1995). The relationship between gender and sleep problems may be related to the gender difference in affective disorders. Women are more prone to anxiety which is associated with sleep problems (Krishnan & Collop, 2006). The comparison of our hypotheses tests with and without these control variables yields identical results. Thus, to maximize statistical power and offer the most interpretable results, we report the results without controlling for age and gender (Bernerth & Aguinis, 2016).

Analysis Strategy

The data have a hierarchical structure with workdays nested within persons. To account for dependency in the data, we performed multilevel structural equation modeling (MSEM) with Mplus, version 8.4. The ICC values of daily justice, daily negative emotions, and daily sleep problems are respectively, 58%, 72%, and 63%. This suggests that a significant amount of variance is explained by within-person variation, justifying our multi-level approach. Specifically, we used MSEM with latent variables to assess whether daily interpersonal peer justice is related to daily sleep problems via daily negative emotions at the within-level of analysis, and whether this relationship is moderated by dispositional optimism, a between-person variable, through a cross-level interaction. To test for this cross-level interaction, we first created a random slope at the within-level of analysis for the relationship between justice and affect. At the between-level, we regressed this random slope on the level-2 moderator, dispositional optimism. Optimism as a trait variable is integrated in our model as a level-2 variable and grand-mean centered. All other variables (justice, negative affect, and sleep) are measured at level-1 on a daily basis. All the indicators relative to these level-1 variables are allowed to vary at both levels.

We followed the recommendation of Newman (2014) to use all data available. We thus include as many participants and data points as possible using a missing data treatment to have the maximum power to test the cross-level interaction (Mathieu et al., 2012). We apply the Full Information Maximum Likelihood (FIML) procedure in Mplus to deal with our missing data¹. The data is available at: https://osf.io/9rbsd/?view_only=fab2a9a554d44d58ba8acdc422efbdde.

Results of Multilevel Structural Equation Modeling

The descriptive statistics and intercorrelations for the study variables are shown in Table 1. We started with a multilevel confirmatory factor analysis (MCFA) to examine the construct validity of our study variables. In the MCFA, we included the four variables and their indicators: daily interpersonal peer justice (4 items), daily negative affect (10 items), daily sleep problems taken from the following day (3 items), and dispositional optimism (6 items). Interpersonal peer justice, negative affect, and sleep problems are modeled at both the within- and between-level, whereas optimism is modeled at the between-level only. We let the error terms of two sets of negative affect items with close meaning (afraid and scared - ashamed and guilty) covary. This four-factor model showed an acceptable fit with the data (X² (336) = 1570.60; RMSEA = .05; CFI = .89; SRMR within = .05; SRMR between = .06), and all indicators load significantly on their respective constructs. We tested the discriminant validity of our level-1 variables through a series of CFAs conducted at the within-level. The three-factor model (interpersonal peer justice, negative affect, and sleep problems (X² (116) = 1524.95; RMSEA = .08; CFI = .91; SRMR = .05) provides better results than any other model (interpersonal peer justice and negative affect collapsed: ∆χ2 = 3326.9, ∆df = 1, p < .01; interpersonal peer justice and sleep problems collapsed: ∆χ2 = 678.87, ∆df = 1, p < .01; negative affect and sleep problems collapsed: ∆χ2 = 587.59, ∆df = 1, p < .01; a one-factor model: ∆χ2 = 3878.43, ∆df = 3, p < .01).

Table 1.

Descriptive Statistics and Correlations for Study Variables.

Variable	M	SD	1	2	3	4
1. Interpersonal peer justice	4.25	.66	—	−.52**	−.31**	.34**
2. Negative affect	1.65	.72	−.45**	—	.43***	−.46**
3. Sleep problems	2.48	.98	−.26**	.33**	—	−.28**
4. Optimism	3.69	.72	—	—	—	—

Note. Correlations above the diagonal are based on between-person averages (N = 251), whereas correlations below the diagonal are based on within-person data (N = 1778).

*p < .05. **p < .01.

We then tested our model stepwise following the recommendation by Aguinis et al. (2013). We tested a multilevel mediation model at the within level with random intercept (-2LL = 60,198.43; pseudo-R2 = 28.21%). Then, we tested a model in which we allow the interpersonal peer justice – negative affect slope to vary (-2LL = 59,963.96; pseudo-R2 = 56.88%). This model exhibits a significantly better fit to the data in comparison to the previous model (Δ-2LL (1) = 234.47; p < .01). Finally, we added the cross-level interaction and showed that our final model fits the data significantly better than the previous one (-2LL = 59,959.53; pseudo-R2 = 57.34%; Δ-2LL (1) = 4.43; p < .05).

As expected, the unstandardized results of the multilevel analyses indicate that at the within-level of analysis, daily interpersonal peer justice is negatively associated with daily negative affect (estimate = −.48, s. e. = .06, p < .001, see Figure 1). Hypotheses 1a and 1b state that dispositional optimism (level 2) moderates the level-1 relationship between daily interpersonal peer justice and daily negative affect. To test this hypothesized cross-level interaction, we regressed the random slope between interpersonal peer justice and negative affect on the person-level dispositional optimism variable. Consistent with Hypothesis 1b, the results show that the interaction between daily interpersonal peer justice and dispositional optimism is significant (estimate = .36, s. e. = .18, p < .05), suggesting that interpersonal peer justice is particularly experienced as negative in terms of daily negative affect by employees who are low (vs. high) in optimism.

Figure 1.

Moderated mediation model (unstandardized coefficients). *p < .05; **p < .01

The interaction effect is explained using the Johnson-Neyman (J-N) technique in Mplus after standardizing the moderator. The Johnson-Neyman technique provides a visual representation of the values of the moderating variable optimism (on the X-axis) at which the association between interpersonal peer justice and negative affect is statistically significant (i.e., where the effect line and its 95% CI do not overlap with zero on the Y-axis), highlighting the strength of the association across the values of the moderating variables. As shown in Figure 2, the effect of interpersonal peer justice on negative affect systematically increases as the level of optimism increases. More specifically, the effect of interpersonal peer justice on negative affect is non-significant for high levels of optimism because the confidence intervals of the effect contain zero for high levels of optimism. Also, the strength of this negative relationship increases as the level of optimism decreases. Overall, Hypothesis 1b is thus supported.

Figure 2.

Johnson-Neyman plots of simple slope and 95% confidence interval for interpersonal peer justice on negative affect for different values of optimism. Plot lines represent effect (red line) and 95% CI of effect (blue lines).

In addition, negative emotions are positively related to daily sleep problems at the within-level (estimate = .30, s. e. = .04, p < .001), and the direct effect of interpersonal peer justice on sleep problems is still significant (estimate = −.14, s. e. = .04, p < .001). The indirect effect of the mediating relationship between daily interpersonal peer justice and daily sleep problems via negative emotions is negative and significant at the within-level (estimate = −.15; s. e. = .03, p < .001; 95% confidence interval = [−.20; −.09]). Thus, Hypothesis 2 is confirmed, and our full model is empirically validated.

Discussion

Daily interactions with peers regularly bring about experiences of injustice. In the present paper, we investigate the moderating effect of favorable expectations about the future (optimism) on the effects of such experiences. We find that higher optimism leads to less negative emotional reactions, and in turn, fewer sleep problems following perceived interpersonal mistreatment. Our study contributes to both organizational justice and optimism research.

To the best of our knowledge, this study is the first to investigate optimism as a predictor of differences in reactions to daily injustice experiences. The focus on optimism is both theoretically and practically relevant. Of theoretical interest is the mechanism by which a cognitive thinking style, namely, dispositional optimism, explains affective reactions to workplace justice experiences. Interesting here is that optimism describes the tendency to have favorable expectations about the future. In particular, we find that a cognitive style in terms of how individuals think about the future explains the affective reaction to an event, illustrating that cognitive and emotional aspects are intertwined in shaping reactions to daily justice encounters. With regard to the justice literature, this highlights the importance of considering the temporal aspects of justice reasoning. While it has long been argued that past injustice leads to the anticipation of future injustice (Shapiro & Kirkman, 1999), our findings suggest that in some way, via cognitive styles, anticipations are already factored into reactions to present injustices. It would be interesting to further investigate this effect in relation to more specific anticipations as well as different anticipation timeframes.

The demonstrated role of optimism in how employees react to injustice events has important implications for organizational practice. In particular, optimistic thinking is trainable, and individuals can learn to change their thinking style (Seligman, 2006). The psychology literature suggests various interventions to improve the level of optimism. For example, companies can implement programs to increase mindful awareness in occupational settings in order to develop optimism (Malinowski & Lim, 2015). Previous research has shown that an eight-week online mindfulness-based program increases optimism and subsequent positive attitudes in the workplace (Heckenberg et al., 2019). A particularly effective intervention for increasing optimism appears to be the Best Possible Self intervention, which entails creating objectives for and envisioning an ideal future version of oneself (Malouff & Schutte, 2017). It involves writing about one’s best possible self in the future, once everything has gone as well as it can (Loveday et al., 2018). These interventions range in duration from 1 day to 2 months, and in intensity from 10 to 75 minutes per week. The longer the intervention, the greater the potential effect on optimism (Carrillo et al., 2019). Finally, instead of offering employees positive psychological programs, organizations can foster optimism by providing good working conditions. In their recent five-wave longitudinal study, Li et al. (2019) show that a decrease in job insecurity leads to an increase in dispositional optimism, in turn promoting a further decrease in job insecurity later on. In another study, Lu et al. (2018) suggest that supervisor work engagement may trickle to employees’ optimism because the leader’s level of work engagement communicates positive information, in turn cultivating a sense of optimism and positive anticipation about future outcomes among followers. In addition, leaders with high work engagement often experience positive emotions. As leaders are influential figures, their subordinates tend to pay attention to their emotional expressions and integrate their positive feelings through optimism. While such interventions may make employees feel better about their immediate daily workplace interactions (i.e., feel less daily negative effects and suffer from fewer sleep problems), they cannot attack the root of the problem – the transgression of justice rules. Arguably, an employee who feels less negatively about an injustice may even be less likely to confront the wrongdoer and attempt to change the offensive behavior. These propositions remain to be tested in future research.

As our affective events framework highlights, the experience of work consists of many daily interactions that take place within groups and inside organizations. The present study focuses on within-person dynamics with a between-person moderator without taking into account the important moderator effects at the group and organizational level. Future studies on the interaction effects between different levels may provide interesting insights. For example, an organizational climate that is reassuring and provides high certainty will already serve as a buffer for experiences of injustice, perhaps leaving less room for optimism to serve as a buffer. In addition, the effects we find may be altered by the frequency of mistreatment. The mistreatment literature suggests that some competitive performance-based reward systems and excessive goal setting increase competition and tension among employees (Ordóñez et al., 2009). Such systems are therefore likely to be associated with increased incidents of impolite and insensitive interpersonal behavior. Will optimism still serve as a buffer if such incidents continue to occur? Or will the reverse buffering effect eventually take over?

With regard to the optimism literature, our study contributes to an ongoing and unresolved controversy, namely the conflicting possibilities of a “buffering” versus a “reverse buffering” effect of optimism when dealing with negative workplace experiences. Our findings provide evidence of the buffer hypothesis, but not the reverse buffer hypothesis. In other words, we find that dispositional optimism protects employees from daily negative experiences, as such experiences are associated with fewer negative emotions and consequently fewer sleep problems. This finding may seem surprising in light of several studies that, conversely, find support for the reverse buffer effects of dispositional optimism. However, important to note is that these other studies test the moderating effects of optimism on between-person and not within-person effects. For example, Hochwarter and Thompson (2010) find that optimism amplifies the negative effects of perceived politics on job satisfaction and stress. Their three studies have a cross-sectional design (even though the first study separates the measurement of the independent and the dependent variable). In other words, people who were more optimistic also react more negatively to perceived workplace politics in general. Similarly, Britton et al. (2012) find that optimism strengthens the relationship between undermining behavior and stress, health and intentions to quit. They also test between-person effects in a large cross-sectional survey relating to general workplace statements rather than specific events (e.g., “Other people take credit for my work or ideas,” “People at work treat me in a manner that puts me down or address me in unprofessional terms, either publicly or privately,” and “People at work fail to give me information that is necessary to do my job”). To shed light on how the effects differ between levels, the moderating effects on both within-person and between-person effects need to be examined in the same study.

In addition, the aforementioned studies rely on a generalized assessment of the quality of workplace relationships. Arguably, the findings suggest that optimists may react more negatively to poor workplace relationships that severely disappoint their overall positive expectations (Carver et al., 2010) as well as their strong belongingness goals (Castellani et al., 2016). In contrast to these studies, we examine specific daily events that constitute the upswings and downswings that create workplace relationships over time. Indeed, optimists may not react as negatively as pessimists to daily negative interpersonal events, which helps them build better relationships in the long run. However, our finding is not inconsistent with previous between-person studies: when optimists’ long-term relationships fail despite their positive spin on daily events, they may react particularly negatively. Therefore, a more nuanced temporal perspective differentiating between event versus relationship judgments could help reconcile the contradictory theoretical and empirical evidence for the reverse buffer and buffer hypotheses of optimism. Such research would also help to refine our understanding of the short-term versus long-term effects of positive expectations/optimistic reasoning and enable new theory building along these lines. For example, future studies of the effects of optimism on justice dynamics at work might usefully include both entity justice (e.g., the general justice of a supervisor, of a peer, of an organization across events) and event justice (e.g., specific incidents or daily evaluations). Such studies may be able to reconcile the conflicting findings on the buffer and reverse buffer effects.

These temporal effects pose interesting challenges for practice. For example, researchers have suggested that it might be helpful to offer employees “realism” training to avoid negative reverse buffer effects (Britton et al., 2012). The present study suggests, however, that realism training could have negative day-to-day effects and could thus hinder the development of better relationships over time. In addition, there may be an optimal level of optimism, such that extreme levels may be dysfunctional and make the positive daily buffering effects less likely. This is because when expectations are extremely high and unrealistic it becomes very difficult to put a positive spin on an injustice experience due to the known limitations of motivated justice reasoning in the face of overwhelming evidence (Barclay et al., 2017). Similarly, the benefits of optimism may depend on the situation and the outcome at stake. In the present study, we focus on affective and sleep outcomes. Performance and career outcomes, for example, may have different dynamics, with less optimistic individuals benefiting from increased preparation for all possible outcomes. Future research could usefully include different types of outcomes in the same study.

Finally, our focus on sleep as a downstream outcome of peer injustice experiences and negative affect also allows us contribute to the rapidly growing literature on sleep as an important work phenomenon. Following numerous studies confirming the effects of organizational justice on wellbeing, we argue that justice affects sleep through negative emotions. In this study, we integrate affective events theory with the optimism literature to better understand the far-reaching effects of transient justice in the workplace. While previous research consistently shows that unfairness can lead to sleep problems, the reasons for this relationship remain unclear. Our study shows that negative affect is an important mechanism underlying this relationship.

Limitations

Our study has several limitations. First, we rely on employees’ self-reports, which may introduce common-method variance. Nevertheless, self-reports are the most appropriate method for assessing our focal variables (i.e., perceived transgression of justice rules, negative affect, and dispositional optimism). Future studies could test the effects of optimism on behavioral outcome variables assessed by coworkers or peers. In addition, to more reliably test the relationship with sleep, future studies should be conducted in sleep laboratories or with sleep tracking devices and include objective measures as dependent variables, such as sleep quantity and quality. In addition, our logic suggests that counterfactual thinking is at least partially responsible for our proposed relationships, even though we do not measure it. Future research could explicitly measure expectations about what treatment can and should be expected at work. We also use online panel data to test our model. Although researchers consider online panel data an appropriate source for academic research (Walter et al., 2019), there are still concerns about the reliability of the data and the sample characteristics compared to traditional sampling techniques. Future research could replicate our study using a sample of employees from one or more identified organizations.

Second, our daily diary approach is unable to provide insights on the longer-term dynamics, and whether the within-person buffering effect extends to longer time intervals (e.g., monthly) remains to be tested. Nevertheless, our focus on the daily effects offers interesting insights beyond those of longer-term studies on the justice-sleep relationship. Most evidence on the justice-sleep relationship comes from epidemiological studies in which the variables are measured over several months (e.g., Hietapakka et al., 2013), a timeframe that is appropriate for studying long-term health effects. In fact, both long and short timeframes are important and related, as long-term health problems often result from an accumulation of short-term problems (Ohly et al., 2010), especially in the case of sleep (Åkerstedt et al., 2009). This is consistent with our theoretical framework of affective events theory, which suggests that individual work events can have important and lasting consequences through their accumulation.

In this study, we consider only justice coming from peers and its interpersonal form. It remains to be tested whether the same results hold for other dimensions of justice (procedural and distributive) and/or sources of justice (organization, supervisor, and customers), potentially with different time frames (e.g., distributive justice decisions from an authority tend not to be experienced on a daily level). While our reasoning about interpersonal peer justice may be applicable to other types of justice, future research could further explore the implications of dealing with this specific form and source of justice from a theoretical and empirical perspective.

Finally, we acknowledge that the relationship between sleep and emotion is likely to be bidirectional and complex. When people sleep poorly, they are more likely to experience negative emotions, have weaker emotion regulation (Fairholme & Manber, 2015), and thus may be more sensitive to justice issues (Kahn et al., 2013). In the present study, we focus on only one aspect of the complex affect-sleep relationship by measuring the relationship between affect on one day and sleep problems the following night. Future research could usefully assess affect in the evening and both sleep quality and affect the following morning to provide a more detailed picture of the reciprocal effects between affect and sleep.

Conclusion

In conclusion, we hope that our study illustrates the promise of investigating dispositional optimism in the context of fairness dynamics. Such research can inform not only the justice literature, but also the optimism literature, where a more nuanced temporal perspective that distinguishes between event and relationship judgments could help reconcile the conflicting theoretical and empirical evidence for the reverse buffer and buffer hypotheses of optimism. Our findings that optimism can serve as a “buffer” against daily interpersonal treatment experiences highlight the potential of optimism interventions.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Associate Editor: René Schalk and Joannes Kraak

ORCID iDs

Marc Ohana

Marion Fortin

Note

Author Biographies

Marc Ohana is Professor of Organizational Behavior and Human Resource Management at KEDGE Business School. He received his PhD from Aix-Marseille University. His research focuses on organizational justice and well-being. He is the author of a number of peer reviewed articles published in journals such as British Journal of Management, Human Resource Management Journal, Journal of Managerial Psychology, International Journal of Human Resource Management.

Marion Fortin is Professor in Human Resource Management at the Toulouse School of Management. She received her PhD in Organizational Behavior from Trinity College, Dublin. Her main research interest lies in the role of fairness perceptions in the workplace, and how they are linked with morality and social context. Her research has been published in journals such as Journal of Applied Psychology, Journal of Organizational Behavior and Organizational Behavior and Human Decision Processes.

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