The Role of Grit in Education: A Systematic Review

Grit is a non-cognitive factor that has received increased attention lately, since research indicates that it plays a significant role in successful outcomes in many fields, and more specifically in education. Grit is rooted in two facets, perseverance of effort and consistency of interest, captured by the Grit Scale. The current systematic review aimed at investigating the association of grit with positive educational outcomes, by exploring both antecedents and outcomes of grit. We identified 29 studies assessing grit in an educational context, published between 2012 and 2017. The primary findings demonstrated that grit shows weak to moderate correlations with educational variables. Its two facets play different roles, with perseverance being a stronger positive predictor of academic performance. Finally, positive variables, such as hope, positive affect and family relationships can foster grit. However, a deeper understanding of the grit construct is essential to distinguish it from facets of the conscientiousness dimension of personality. The usefulness of findings for policy makers and education professionals is discussed, as well as the importance of reinforcing grit in the educational community in order to nurture character in students and enhance their potential.


Introduction
During the last decade, there has been an increasing interest in identifying factors that make individuals excel and be more successful compared to others of equal intelligence, especially in the field of education (Duckworth, Peterson, Matthews, & Kelly, 2007). Apart from cognitive ability, talent and opportunity, working persistently and vigorously towards a challenging goal, sustaining effort and keeping an unabated interest over long periods of time despite failure, setbacks and obstacles, and phases of stability in the course of progress. Gritty individuals employ stamina to stay on track and attain their goals, contrary to individuals low in grit who get easily bored or disappointed and give up effort or choose alternative actions (Duckworth et al, 2007). Grit is considered a personal quality common in leaders, and an important antecedent of success and excellence in every domain regardless of giftedness or talent (Duckworth et al, 2007;Duckworth & Yeager, 2015).
Grit is embedded in two main facets: perseverance of effort and consistency of interest. Interest is not associated with pleasure in terms of immediate short-term gratification, but rather with meaning. Individuals must first assign a personal meaning to a long-term goal and demonstrate passion to confront the adversity and hardship that may occur when attaining it. A long-term goal needs to be not only significantly meaningful, but also engaging; to sustain the individual's effort and vigor (Perez, 2015). Both facets of grit are fundamental ingredients of success, since perseverance of effort contributes to the achievement of mastery despite failure, and consistency of interest is essential in engaging in deliberate practice to reach mastery (Credé et al., 2016). The distinction between the two aspects of grit is captured by the Grit Scale, a 12-item self-report questionnaire (Duckworth et al., 2007) and its short version, the 8-item Grit Scale-S . Most research considers grit as an overall score on the scale, while there are cases where the two facets are explored as two separate constructs (Credé, Tynan, & Harms, 2016).
During the last decade, the majority of studies have tried to identify the predictive role of grit in academic achievement and other educational outcomes. A series of studies by Duckworth et al. (2007) suggested that grit is a significant predictor over and above IQ regarding successful outcomes in education. Grittier individuals were found to attain higher levels of education, make fewer career transitions, and undergraduates in a high standard university achieved higher Grade Point Averages (GPA) compared to less gritty counterparts. Grit was also a better predictor of West Point military academy summer retention of M. Christopoulou et al. cadets compared to self-control. Additionally, Duckworth, Quinn and Seligman (2009) found that grit and life satisfaction significantly predicted teacher effectiveness measured in terms of the academic performance of their students. A recent meta-analysis by Credé et al. (2016) showed that grit demonstrates moderate correlations with performance and retention, and strong correlation with conscientiousness. The meta-analysis also revealed that the "effort" facet accounts for variance in academic performance above and beyond conscientiousness, indicating it should be explored as a separate construct.
Research on the role of grit in educational outcomes may still be in its infancy; nonetheless, it has already received some criticism. Duckworth et al. (2015) admit that the measurement of grit addresses individual differences, but leaves aside situational factors that may influence success. Anderson, Turner, Heath and Payne (2016) criticize the concept, pointing out, for example, that grit is controversial, often presented as a panacea in research, or as a counterproductive mechanism if it is excessive, that it may undermine equality in education and put the blame on low socioeconomic status students for their poor achievements, or that it is not always linked with creative success.
Based on the above, the present systematic review aims at exploring the role of grit and its two facets in educational and academic outcomes, with the hope of facilitating its understanding. We also hope to detect the factors which may lead individuals to cultivate it as a positive characteristic in their academic and life course. Contrary to the recent meta-analysis by Credé et al. (2016), which has addressed grit in terms of performance and retention, conscientiousness, cognitive ability and several demographic variables, the current systematic review focuses exclusively on the role of grit in the educational sector as presented in the literature during the last six years (2012)(2013)(2014)(2015)(2016)(2017). Hence, the review sets out to answer the following research questions: a) which positive educational outcomes is grit associated with, and which ones can it predict? b) are the two facets of grit (effort and interest) playing the same role in educational outcomes? and c) which variables are predictors of grit in education?

Literature Search and Selection Criteria
Initially, we searched Google Scholar to identify relevant research from 2012 to 2017. Key search terms were "grit$" and/or "effort", "perseverance", "passion", "interest" "non-cognitive" combined with "education", "(academic) perform$", "success$", "achieve$", "school", "college" (the symbol $ was used to broaden the search by identifying words of the same stem). This procedure yielded too many results, since some sources appeared more than once. Scopus database was also searched to retrieve any undetected articles, using the same terms, but search results did not yield any new sources. Therefore, after duplicates were removed, book chapters, magazine articles and poster presentations were eliminated (n = 24), all the remaining available sources relevant to the objective of the systematic review were retrieved. Based on titles and abstracts 150 sources were  Figure 1 illustrates the steps of the search and sifting procedure.

Results
The twenty nine studies that were included in the systematic review are presented in detail in Table 1.

Characteristics of Reviewed Studies
From the 29 studies reviewed, 11 were published in 2017, 9 studies were pub- cross-sectional (86%). There was also 1 longitudinal (prospective) study, 1 study with a pre-post design, 1 study including 2 studies (1 cross sectional and 1 longitudinal study), and 1 genetically sensitive sample research on twin teenage student pairs. All studies used quantitative methods, except for one cross-sectional study that used mixed methods for data analysis. Twenty six studies used regression analyses (90%), amongst other statistical analyses.

Demographic Characteristics
The sample size ranged from 105 to 4813 participants. In all the studies participants were students attending several levels of education (primary school to

Main Results
The reviewed studies addressed all three research questions. Some of them addressed more than one question. Grit has been found to associate with a range of positive outcomes in education, such as academic performance and retention in education. Its two dimensions were found to correlate with different educational variables. Positive psychology variables were found to predict grit in the educational context. Grit and positive educational outcomes. Sixteen studies investigated grit as a unidimensional factor that relates to and can predict several educational outcomes. Most studies found a positive link between grit and academic performance reflected in measures such as GPAs, and other positive educational outcomes, such as retention, to education. Grit predicted unique variance in ADT performance when controlling for agreeableness. Performance on the ADT was associated with individual differences in grit above and beyond demographics, intelligence, and attitudes toward math. Finally, Big Five agreeableness did not confound the association between performance on the ADT and grit. Ivcevic & Brackett (2014) To examine validity of three proposed self-regulation predictors of school outcomes-Conscientiousness, Grit and Emotion Regulation Ability (ERA).  Wolters & Hussain (2015) To investigate the relationship between grit and students' self-regulated learning and academic achievement Cross-sectional study N = 213 university students (88% female; 29% Hispanic, 21% African-American) Correlation, multiple regressions.

Continued
Grit-PE was a predictor for all indicators of SRL (value, self-efficacy, cognitive, metacognitive, motivational, time and study environment management strategies, and procrastination).
Grit-CI was associated only with the latter two facets of SRL. Grit-PE predicted achievement before, but not after, accounting for SRL. Grit-PE was positively associated with faculty-student interaction, college satisfaction, and college GPA in both samples. Grit-CI was negatively related to intent to change careers in both samples, and to intent to change majors at UWL. Regression coefficients predicting all continuous outcomes were significantly greater for Grit-PE than for Grit-CI.
To examine the contributions of three psychosocial variables-grit, hope and academic self-efficacy, -to the prediction of academic achievement above and beyond the contributions of demographic variables and perceived ability.  (2016) To examine relationships between non-cognitive skills of charter and district school students and their academic achievement.
Cross-sectional self-report survey, with administrative and longitudinal data N = 1368 8 th graders from 32 public schools in Boston Correlation, Two Stage Least Squares (2SLS) regression Grit was positively related to attendance, behavior, math and ELA test-score gains between 4 th and 8 th grade at the student level. Grit was not related to test-score gains at the school level. Character and BFI showed small associations with fluid intelligence, and larger associations with knowledge/achievement. Character was significantly correlated with knowledge/achievement outcomes in 89% of the pairs. Grit loaded on "Conscientiousness" as one latent factor, which was found to be 57% heritable. After controlling for fluid intelligence, the genetic component of character, but not the environmental, was still associated with variation in the knowledge/ achievement factor. To explore what non-cognitive factors predict college success, and whether the associations between these factors and student success vary as a function of race or ethnicity. Grit only had a significant relation with achievement for non-citizens and was negatively correlated with depression for all participants. Depression was higher at lower levels of grit for non-citizens **** All participants exhibited grit by working hard to achieve their goals, and proving others wrong. Part of their grit stemmed from their families and communities. Non-citizens employed grit to finance higher education, and succeed in college.
Hill, Burrow & Bronk (2016) To explore the role of purpose and positive affect in predicting levels of grit in students, and examine the longitudinal relationships between these three constructs.  (2017) To investigate the role of grit in improving academic outcomes (academic engagement and productivity) within the university setting, and explore whether demographic variables moderate the relationship between grit and academic success.
Both Grit-PE and Grit-CI correlated positively with academic engagement and productivity. Being the first in family to attend university was weakly associated with an increased level of Grit-PE. Grit-PE, but not Grit-CI had a small significant contribution to the prediction of academic productivity. Both subscale scores significantly predicted engagement, but Grit-PE contributed more than twice in explaining engagement compared to Grit-CI.

Hwang, Lim, &
Ha (2017) To examined the structural relationship between age, grit, conscientiousness, self-control, and academic success, and explore whether grit mediates personality and academic maladjustment.  (2017) To examine (a) the factor structure of grit, (b) its relation to similar constructs, and (c) its predictive power for end-of-semester course grades.
Cross-sectional survey Multidimensional item response theory, multiple regression analyses a) Bifactor model of grit as a single latent construct with 2 subscales (Grit-PE and Grit-CI) fit best in college sample, whereas the 2-correlated model fit best in high school sample. b) For both samples Grit-PE predicted grades more strongly than Grit-CI. c) High school Grit-PE overlapped most with self-control, cognitive self-regulation, and behavioral engagement. College Grit-PE overlapped with self-control and conscientiousness, while Grit-CI overlapped more with cognitive self-regulation, effort regulation, behavioral engagement, and behavioral disaffection. Oriol, Miranda, Oyanedel, & Torres (2017) To observe the effect of grit and self-control on academic self-efficacy and satisfaction with school. Grit-PE and Grit-CI showed non-significant correlations with academic achievement and did not comprise significant predictors.

Akos & Kretchmar (2017)
To explore the predictive validity of self-reported and informant-reported grit on college outcomes. Hierarchical multiple regression, logistic regression, ICC Grit total scores significantly predicted GPA. Self-report grit total score inversely predicted change in major.
Only Grit-PE predicted GPA compared to Grit-CI. Lower grit scores were linked with a higher likelihood to change majors, with only Grit-CI being a significant predictor. Grit considered as a dimension of character also provided consistent results. Tucker-Drob et al. (2016) found that character measures (among which grit) were significantly correlated with the achievement and knowledge outcomes in 89% of twin/triplet pairs of 3 rd to 8 th grade students. Park et al. (2017) explored a tripartite taxonomy of character (interpersonal, intellectual and intrapersonal) in three related studies on 4th to 8th graders. Results showed that only intrapersonal character (which includes grit) was related to higher grades (study 3) and was a significantly predicted class participation and academic achievement (study 1) as well as higher student GPA (study 2). Strayhorn (2014) who explored the role of grit in the academic success of Black male collegians' at predominantly White institutions, concluded that grittier Black males achieved higher grades than their less gritty same-race male peers, and that grit was a positive predictor of college grades, explaining almost as equal variance as high school GPA and ACT score. Similarly, Akos and Kretchmar (2017) found that self-report grit total score significantly predicted GPA in undergraduate students, and Pate et al. (2017) found that grit-total score was an independent predictor of high academic performance in a sample of student pharmacists in the US. Grittier Taiwanese students tended to self-report higher academic performance and increased academic satisfaction in the study by Lin & Chang (2017), while grit was significantly positively associated with academic achievement only for non-citizen Latino first-generation college students in the study by O'Neal et al. (2016). In two studies, the positive relationship between grit and academic performance was mediated by deliberate practice in Korean students (Lee & Sohn, 2017) and by math confidence (for students with lower math confidence the positive effect of grit was stronger) in university students in Canada (Flanagan & Einarson, 2017).
Four studies explored the predictive capacity of grit beyond personality and intelligence in terms of academic performance or achievement, and three in terms of retention in education. Grit predicted unique variance in performance on the Academic Diligence Task (as a behavioral measure of academic diligence, focused on time spent on the task or on productivity of problems solved) in high school seniors, after controlling for agreeableness (Galla et al., 2014). Complementary were the results of the study by Dumfart and Neubauer (2016), who investigated whether non-cognitive traits have incremental predictive capacity over intelligence and conscientiousness in terms of school achievement. Grit correlated moderately with academic achievement criteria, such as GPA, science and language scores. However, only together with other variables, rather than alone, could it account for almost half the variance in adolescent school achievement. Similarly, grit added little phenotypically or genetically to the prediction of academic achievement beyond traditional personality factors, especially conscientiousness in a sample of twins (Rimfeld et al., 2016). Even though grit correlated positively with school satisfaction, school recognition and decreased rule violation, it did not correlate with GPA and academic honors; neither did it explain additional variance in any school outcome compared to conscientiousness in the study by Ivcevic and Brackett (2014).
Interesting was the finding that grit is linked with retention in education. Eskreis-Winkler et al. (2014) found that grit was positively correlated with school motivation and academic conscientiousness, and it remained a significant predictor of graduation, as a measure of retention. Grit predicted retention over and beyond established context-specific predictors of retention (e.g., intelligence) and demographic variables (Eskreis-Winkler et al., 2014). In the aforementioned study by Lee and Sohn (2017), grit significantly predicted career preparation behavior and major-career relatedness when Big Five personality traits were controlled for. Complementary were the findings by Akos and Kretchmar (2017) where self-report grit total score inversely predicted change in major in a sample of first-year undergraduate students.
Grit was also related to a variety of educational outcomes apart from academic performance. In the study by West et al. (2016) which examined relationships between non-cognitive skills and academic achievement in charter and district school students, grit was positively related with math and ELA test scores, as well as attendance and behavior at the student level. Grit was also positively related to academic-self efficacy at primary and secondary school level, but only with satisfaction with school at secondary school level (Oriol et al., 2017).
Overall, results regarding the first research question are homogeneous. Grit is linked with various positive educational outcomes. It is positively correlated mainly with academic performance and achievement, although correlations do not reach strength. However, rarely does it show incremental predictive validity over other predictors (such as personality) regarding achievement, but it has satisfactory predictive capacity regarding retention in education.
The two facets of Grit and educational outcomes. Thirteen studies explored grit in terms of its two facets and found that they associate differently with educational outcomes. In the reviewed studies there was no consensus regarding the way in which the two facets of grit correlate with academic performance. Yet, results on the variables predicted by each of the two facets of grit were quite consistent.
High performers reported higher Grit-PE and Grit-CI scores compared to average or low performing Taiwanese students (Lin & Chang, 2017) and student pharmacists in the US (Pate et al., 2017). Both Grit-PE and Grit-CI showed weak correlations with the GCSE of twin teenage students in the UK (Rimfeld et al., 2016), positive correlations with estimated grade (Weisskirch, 2016) as well as academic engagement and productivity (Hodge et al., 2017) in undergraduate students, and were associated with a lower expectation of changing majors (Bowman et al., 2015). Dixson et al. (2016) who examined talented students found that Grit-PE positively, but moderately, correlated with academic achievement, whereas Grit-CI displayed a same strength negative correlation.
However, Dixson et al. (2017) found that Grit-PE and Grit CI showed non-significant correlations with academic achievement of African American high school students, and neither comprised a significant predictor.
A number of studies found that each facet of grit is associated with different variables. Grit-PE was negatively correlated with academic maladjustment (Hwang et al., 2017) and positively associated with GPA (Bowman et al., 2015;Farruggia et al., 2016), achieved grade (Weisskirch, 2016), motivation, academic self-efficacy, and time management (Farruggia et al., 2016). It also correlated positively with college satisfaction, faculty-student interaction, and co-curricular engagement, while Grit-CI was related to less intent to change careers (Bowman et al., 2015), procrastination, time and study environment management strategies (Wolters & Hussain, 2015). Another interesting finding was that being the first family member to attend university was linked to higher levels of student Grit-PE (Hodge et al., 2017).
Generally, Grit-PE was found to be a more powerful predictor of academic performance and retention compared to Grit-CI. In the study by Hodge et al. (2017) in Australian university students, Grit-PE, but not Grit-CI, showed a small significant contribution to the prediction of academic productivity measured in perceived academic performance. In the same study, both Grit-PE and Grit-CI significantly predicted academic engagement, but Grit-PE contributed more than twice compared to Grit-CI. Similar results come from the following studies. Only Grit-PE predicted GPA compared to Grit-CI in undergraduate university students (Akos & Kretchmar, 2017), grades in both high school and college student samples (Muenks et al., 2017), GCSE in high school students in the UK (Rimfeld et al., 2016), as well as higher GPA, greater academic adjustment, and intent to persist in college (Bowman et al., 2015). Wolters and Hussain (2015) found that Grit-PE predicted academic achievement as well as all self-regulated learning indicators (such as self-efficacy, cognitive, metacognitive, motivational, time and study environment management strategies), and was the only significant predictor of estimated grade reported by undergraduate students in the study by Weisskirch, 2016). Perseverance significantly predicted academic achievement and consequently retention, reflected in progression to the next year of studies (Farruggia et al., 2016). Hwang et al. (2017) found that only Grit-PE had a positive indirect effect on GPA scores and it mediated the negative relationship that conscientiousness and self-control had with academic maladjustment. The reviewed studies only showed that Grit-CI was a significant negative predictor of the likelihood of undergraduate University students to change majors (Akos & Kretchmar, 2017).
In conclusion, findings agree that perseverance of effort and consistency of interest function as two separate variables, with Grit-PE being a stronger positive predictor of academic performance compared to Grit CI.
Variables predicting grit in education. The reviewed studies that investigated the factors that predict grit in education were seven. Four studies revealed that factors related to hope, meaning and connection predict grit. Hill et al. (2016) found that purpose in life and positive affect were unique positive predictors of students' grit. Vela et al. (2015) found hope to be the strongest positive predictor of grit in Latino students, and search for meaning the strongest negative one, while first generation Latino students' families and communities were found to play an important role in grit (O'Neal et al., 2016). Lin and Chang (2017) also found that perceptions of family influence and Big Five personality traits (apart from extraversion) were significant predictors of Taiwanese students' grit, with conscientiousness being the strongest one.
Factors associated with learning also emerged as predictors of grit in three studies. Akin and Arslan (2014) found that learning (mastery) approach goal orientation was the strongest positive predictor of grit, while learning-avoidance and performance approach/avoidance goal orientations significantly negatively predicted grit. Findings by Yeager et al. (2014) revealed that a self-transcendent purpose for learning predicted greater personal meaningfulness of schoolwork, grit, academic self-control, and performance on boring math problems of the Academic Diligence Task, and increased both the attempt towards deep learning from such a task, and course grades for all students, but especially for low-performers. Additionally, a self-oriented, intrinsic motive for learning was a significantly weaker predictor of reported grit compared to a purpose for learning. Finally, Weisskirch (2016) found that self-esteem and general strategies for learning predicted both facets of grit, while attitudes toward lifelong learning also predicted Grit-PE.

M. Christopoulou et al.
In summary, the few studies that have investigated predictors of grit in education have shown that both positive psychology variables such as hope, meaning and connection, and learning factors, such as learning approach-avoidance goal orientation and a self-transcendent purpose for learning, predict grit.

Discussion
The purpose of this systematic review was to investigate the role that grit plays in education and explore its outcomes and its antecedents. Twenty out of the twenty-nine reviewed articles were published in 2016 and 2017, indicating the increasing interest in this field of research. The review provided a range of emerging findings from quantitative studies on the role that grit plays in education.
Consistent with previous studies (Duckworth et al., 2007), grit as an overall score was positively associated with various educational outcomes related to academic achievement and retention in education. Grit was positively associated with measures of academic performance, such as GPA, GCSE, ACT scores, science and language scores, as well as with more behavioral outcomes, such as school motivation, attendance and behavior, academic conscientiousness, satisfaction with school/college, decreased rule violation, and performance on the ADT task (e.g. Bowman et al., 2015;Farruggia et al., 2016). It also displayed positive associations with mastery approach goal orientation (Akin & Arslan, 2014). However, in line with the findings of Credé et al. (2016), correlations between grit and most educational outcomes were weak to moderate in the majority of studies. This might be explained by the fact that there could be other factors mediating this relationship, such as math confidence (Flanagan & Einarson, 2017) or deliberate practice (Lee & Sohn, 2017).
Contrary to previous assumptions, only a few studies showed that grit had incremental predictive validity over other predictors regarding performance and retention (e.g. Eskreis-Winkler et al., 2014;Strayhorn, 2014). When variables such as intelligence or personality traits, and more specifically conscientiousness, were explored together with grit, the latter lost its predictive power (Dumfart & Neubauer, 2016). This indicates that maybe the construct is not operationalized satisfactorily or that grit is part of or overlaps significantly with the conscientiousness personality dimension (Credé et al., 2016). Therefore, there is a need for further studies to help better conceptualize grit and differentiate it from other, related, constructs. Studies confirming the two-factor structure of grit revealed that "perseverance of effort" was a stronger predictor of academic performance compared to "consistency of interest" (e.g. Bowman et al., 2015;Muenks et al., 2017;Wolters & Hussain, 2015). Perseverance of effort was associated with self-regulated learning strategies, academic engagement and performance in the university (Hodge et al., 2017), whereas consistency of interest was associated with decreased likelihood of university students to change majors (Akos & Kretchmar, 2017) and less intent to change careers (Bowman et al., 2015). This indicates that a sus-tained interest in a specific area is more linked to a long-term goal, since selection of a major is intertwined with career intention and they both are future-oriented. The findings that perseverance of effort and consistency of interest function as two separate variables suggest that the construct of grit needs further research, since it is not clear whether it is better to be conceptualized as a unidimensional construct, or as two separate variables.
Perseverance of effort was found to correlate strongly or overlap with conscientiousness in many studies (e.g. Dumfart & Neubauer, 2016;Ivcevic & Brackett, 2014). This may indicate first of all that the two dimensions of grit behave differently, and that only perseverance may be closer to grit as a construct. Rimfeld et al. (2016) argued that the etiology of grit is highly similar to other personality traits such as conscientiousness, by sharing a genetic instead of environmental background, which accounts for associations between character and academic achievement, a finding in agreement with the study of Tucker-Drob et al. (2016). These findings indicate that the current measurement of grit with the Grit Scale does not differentiate the construct considerably from conscientiousness, and does not raise its predictive validity over and above factors such as personality, supporting already contradictory claims regarding grit and conscientiousness (Abuhassàn & Bates, 2015;Perez, 2015).
Although there is scarce research on predictors of grit in education, the reviewed studies revealed that grit can be predicted by two main factors. The first are concerned with learning, such as mastery orientation goals (Akin & Arslan, 2014) or a self-transcendent model of learning (Yeager et al., 2014). The second group of factors has to do with positive psychology variables intertwined with connection and purpose, such as hope, purpose in life and commitment, positive affect (Hill et al, 2016;Vela et al., 2015), and perceived family influence, conceptualized as psychological and social support (Lin & Chang, 2017). As the mixed methods study by O'neal et al. (2016) revealed, college students' grit stems from their relationships with family and community. These findings together suggest that strengthening family and community bonds, improving communication and relationships between family, community, schools and learners as well as fostering a positive and supporting school climate could enhance grit (or even perceptions of grit), and consequently successful outcomes in education (Duckworth, & Yeager, 2015). Attention should be given especially to ethnic minority groups, where fostering grit could function as a means towards educational success, where learners should be supported to sustain efforts to stay engaged with their studies, despite perceived social inequities or limited access to resources, and regardless of talent. Hence, it seems that more qualitative studies are essential to reach depth of knowledge regarding the antecedents of grit that play an important role in education.

Strengths and Limitations
The current systematic review comprises the first attempt to gain an insight into the antecedents and outcomes of grit in education. Even though literature on this field is still at its infancy, we managed to spot twenty nine journal articles that provided valuable information on the topic. Its importance lies in the fact that it unveiled a number of factors that can predict grit. Hence, it provided the first step towards a more in depth exploration of the processes and characteristics that underlie grit and keep individuals going towards pursuing their goals.
A number of limitations of this review need to be addressed though. First of all, selection of studies entails two drawbacks. The emerging interest in the role of grit in education was manifest in unpublished research papers, such as doctoral dissertations, and working papers that were not included in the review due to rigorous inclusion and exclusion criteria. Furthermore, the majority of studies selected used self-report scales and questionnaires, amongst which the Grit Scale, which might have biased the selection process, therefore, restricting generalizability of findings. Specifically, the Grit Scale is a self-report questionnaire that has received much criticism not only by researchers but also from its developers. Duckworth (2007) admits that the scale is susceptible to social desirability bias, entails retrospective reflection since participants have to respond to items by thinking of their usual past behavior, and finally, does not take into consideration situational variables that may affect successful performance (Duckworth et al., 2007;Duckworth, & Yeager, 2015). It seems to be a measure that identifies and indicates individual differences, ignoring environmental and social influences to success. All these, although beyond the scope of this review, raise many issues about whether research on grit is directed to learners of the same level tested against the same outcome measures, or to individuals who belong to minorities, have access to limited opportunities, and may be vulnerable to discrimination due to exam performance. As Shechtman, DeBarger, Dornsife, Rosier and Yarnall (2013) claim, individuals are at risk of being accused of poor performance due to lack of grit, instead of lack of critical support and opportunities in their educational environment. This last point could be one new insight into the measurement of grit, which is linked with the antecedents of the construct as well. Moreover, the review was vulnerable to sample bias. Grit was found to predict performance in some samples but not in others, indicating that such new constructs should be assessed in a wider range of samples before assuming generalization (Dixson et al., 2016). Some studies aimed at specific samples (talented students, particular schools, students with high GPAs) and the majority of studies used samples where females outnumbered males. Furthermore, students from ethnic minorities comprised a large proportion of the samples studied. All these factors raise important ethnic group, cultural and gender issues. Ethnic minority students may carry the stigma or stereotype and may put maximum effort to achieve their academic goals, hence scoring higher in self-reports of grit (e.g. Strayhorn, 2014;Weisskirch, 2016). Empirical evidence suggests that women attribute academic success to effort and are more motivated by academic rewards, whereas men link their success to their ability (Lindo, Sanders, & Oreopoulos, 2010), so gender differences in grit are yet to be further explored.

M. Christopoulou et al.
Additionally, there were scarce studies that explored long-term goals, which is the actual object of reference of the grit concept according to Duckworth et al. (2007). Most of the studies used cross-sectional designs, addressing outcomes within a small time frame rather than investigating grit for long-term goals.
Prospective studies investigated participants over short periods of time, most studies focused on standardized test scores rather than actual learning processes, and no study explored whether goals were meaningful to participants instead of perceived as merely an endpoint in the educational process.

Implications and Avenues for Future Research
Findings indicate that there is ground for research and practice regarding grit and its antecedents in education. It seems that individual factors are not the only ones that contribute to the occurrence of grit; situational and environmental factors also play an important role. Hence, by understanding the factors that can make individuals grittier, researchers and educators can work on specific programs and projects to enhance grit, not only in learners but in the entire educational community. Targeted actions to nurture a positive educational environment with support networks and strong relationships among members could offer a sense of belonging and foster hope in an effort to keep individuals' efforts focused on their long-term educational goals.
Future research should consider a broad range of issues. First of all, updated or supplementary instruments need to be developed to measure grit more accurately, and clarify its structure and its relation to conscientiousness. More focus should be directed on the "perseverance of effort" as a distinct facet and its role in educational outcomes. This will facilitate a deeper understanding and will allow for the development of adequate interventions, such as the employment of character strengths to nurture and strengthen grit (Perez, 2015). Studies should also use repeated measurements and collect scores on exams across time instead of only relying on final exam scores to measure performance in educational contexts, in an effort to assess learning and acquired knowledge.
Additionally, longitudinal studies should explore whether its two facets remain positively correlated in the face of long-term adversity, situational changes or personal goal modification. It could also be investigated whether grit remains the same across all educational settings, e.g. whether individuals report the same level of grit in school or in computer or foreign language education, and whether it is retained after education completion, e.g. in relevant work environments. It would also be interesting to investigate grit of individuals who choose to pursue a career in the Academia, e.g. doctoral students and researchers. Grit should be investigated in separate groups of students, since different levels of grit may appear in talented students, ethnic minority students, students of different educational levels, or even students that come from collectivistic and individualistic cultures. Additionally, grit could be explored in cases of learning disability as well as in terms of setting variation, e.g. differences in grit between learners of regular versus Montessori school settings, or even distance learners. Finally,