# **1. Introduction**

A growing literature in psychology and economics shows that socio-emotional skills play a key role in predicting education and labor market outcomes (Alan et al., 2019; Acosta and Muller 2018; Kautz et al., 2014; Borghans et al. 2008a, 2008b; Heckman et al., 2006). Attributes related to self-regulation, in particular, have been found to be strong predictors of these outcomes (Levin et al., 2016; Heckman and Kautz, 2014; Stecher and Hamilton, 2014; Naemi et al., 2013;; Tough, 2012; Willingham, 1985). Among these, grit – the ability to sustain effort and interest towards long-term goals (Duckworth et al., 2007) – has been found to predict various outcomes at levels comparable to IQ and conscientiousness (Eskreis-Winkler et al., 2014, 2016; Maddi et al., 2012; Duckworth et al., 2007).

In cross-section samples, adults who score high on grit (who are ‘gritty’) make fewer career changes, progress further in their formal education, and earn higher GPAs (Duckworth et al., 2007). Prospective longitudinal research looking at grit and achievements finds that, for example, in education, grit has been found to improve school performance in standardized tests (Alan et al., 2019); predict school graduation (Eskreis-Winkler et al., 2014); and predict the ranking of students in high-stakes competitions such as the National Spelling Bee (Duckworth et al., 2007). These findings support a growing emphasis on integrating socioemotional skills into formal education (OECD, 2015; Guerra et al., 2014).

Grit has a strong relationship with conscientiousness, and in a nomological network of conscientiousness, represents its proactive aspects centering around industriousness and self-control (Roberts et al., 2005).<sup>2</sup> It has two distinct, albeit related, facets: _(i)_ perseverance of effort (i.e. working strenuously towards challenging goals over long periods of time despite failure, adversity, or plateaus in progress); and _(ii)_ consistency of interest (i.e. maintaining effort and interest for long-term goals without losing focus) (Duckworth et al., 2007; Duckworth and Quinn, 2009). The former correlates strongly with the productiveness facet of conscientiousness, while the latter does not, suggesting grit adds to the construct (Schmidt, Lechner and Danner 2020).

Given its importance in determining critical human development outcomes, is it possible to cultivate grit in schools? Evidence from small-scale interventions (with limited sample sizes in single classrooms or schools) suggests that the answer is “yes” (Alan et al., 2019; Eskreis-Winkler et al., 2014). But can it be done at scale? To answer this question, we designed and implemented a nationwide intervention to teach grit to middle-school students in North Macedonia. In spring 2016, all sixth and seventh-grade students in North Macedonia were randomly allocated to receive either one of two grit-building treatments, low or high-intensity, or to make part of a control condition. In the high-intensity treatment, both students and teachers are exposed to the intervention, while the lower-intensity treatment relies on student self-paced learning. The intervention consisted of a curriculum that taught and motivated students to adopt the tenets of deliberate practice<sup>3</sup> (to identify stretch goals, get feedback, concentrate, and repeat until mastery), as well as that characteristics such as talent, gender, or ethnicity are not deterministic of achievement. We then measured their socio-emotional

> 2 Grit has a pairwise correlation coefficient with conscientiousness of about 0.8, leading some authors to argue that grit and conscientiousness are in fact the same (Schmidt et al., 2017; Credé et al., 2016; Eskreis-Winkler et al., 2014; Ivcevic and Brackett, 2014). While this debate is ongoing and beyond the scope of this paper, it should be noted that the literature reports a high variance in the strength of correlations (between 0.4 and 0.7), and measures used to assess conscientiousness vary substantially.

> 3 Ericsson (2008), Ericsson et al. (1993).

2