 42. Some Contributions of Economics to the Study of Personality 879
Martins (2010) analyzed data from EPIS 
(Exploration, Preparation, Implementation, 
and Sustainment), a program developed 
to improve student achievement of 13- to 
15-year-olds in Portugal by increasing mo -
tivation, self-  esteem, and study skills. The 
program consists of one-on-one meetings 
with a trained staff member or meetings in 
small groups. The intervention was tailored 
to each participant’s individual skills deficit. 
Overall, the program was successful and 
cost-  effective, decreasing grade retention 
by 10 percentage points. Kautz and Zanoni 
(2019) found similar effects for a mentoring 
program in high schools in disadvantaged 
neighborhoods.
Heckman et al. (2006) used a version of 
Equation 42.3 to analyze the effects of in -
creases in education on measured cognition 
and noncognitive measures.80 Controlling 
for the problem of reverse causality (that 
schooling may be caused by noncognitive 
skills), they found that schooling improves 
both personality and cognitive skills, and 
that these skills, in turn, boost life out -
comes.81 Heckman et al. (2018) estimated 
a sequential model of education to study 
the effects of education on a variety of out -
comes. Correcting for selection into educa -
tion, they found that early cognitive and per -
sonality skills affect schooling choices, labor 
market outcomes, adult health, and social 
outcomes, and that increasing education 
promotes beneficial labor market, health, 
and social outcomes.
Todd and Zhang (2019) confirmed that 
returns to schooling arise in part because 
education improves noncognitive skills. 
They found that these changes are concen -
trated predominantly among individuals 
from poorer families and tend to stabilize 
by the age of 30. Furthermore, some authors 
claim that cognitive and noncognitive skills 
are associated with sorting into different 
job types, and individuals who score high 
on both tend to choose more schooling and 
subsequent employment in white-  collar oc -
cupations. Kassenboehmer, Leung, and Sch -
urer (2018) contributed to this literature and 
provided estimates of the effect of university 
education on the Big Five personality skills. 
Controlling for selection into college, they 
showed that it increases the extraversion skill by 0.3 standard deviations and seems 
to have some impact on agreeableness, al -
though the latter is quite heterogeneous and 
depends on family background.
Cunha et al. (2010) estimated a model of 
the technology of skills formation using lon -
gitudinal data on the development of chil -
dren with rich measures of parental invest -
ment and child skills. They controlled for 
the endogeneity of investment using shocks 
to family income, along with other instru -
ments. Their model is a version of Equation 
42.3. Skills are self-  productive and exhibit 
dynamic complementarity: Current values 
of skills affect the evolution of future skills 
through direct and cross effects. A leading 
example of a cross-  effect is that more mo -
tivated children are more likely to learn.82 
They estimate parameters that summarize 
how past personality skills affect future cog -
nitive skills.
Cunha et al. (2010) found that self- 
productivity becomes stronger as children 
become older, for both cognitive and person -
ality skills.83 It is more difficult to compen -
sate for the effects of adverse environments 
on cognitive endowments at later ages than 
it is at earlier ages. This finding is consistent 
with the high rank-  stability of cognition for 
ages past 10–12 reported in the literature. It 
also helps to explain the evidence on the in -
effectiveness of cognitive remediation strat -
egies for disadvantaged adolescents (docu -
mented in Cunha, Heckman, Lochner, & 
Masterov, 2006; Knudsen, Heckman, Cam -
eron, & Shonkoff, 2006; Cunha & Heck -
man, 2007).
Personality skills foster the development 
of cognition, but not vice versa (see Cunha 
et al., 2008a; Cunha et al., 2010). It is rela -
tively easier at all stages of life to compen -
sate for early disadvantage in endowments 
by boosting personality skills.84 However, 
personality seems to stabilize around the age 
of 30.85 Thus, the most effective adolescent 
interventions target personality skills.86
Some life experiences, such as employ -
ment, can also improve personality. Using 
a randomized controlled trial, Gottschalk 
(2005) found that working at a job can im -
prove locus of control, a trait related to neu -
roticism, that measures the extent to which 
individuals believe that they have control 