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Reducing Crime and Violence: Experimental Evidence
from Cognitive Behavioral Therapy in Liberia†
By Christopher Blattman, Julian C. Jamison, and Margaret Sheridan*
We show that a number of noncognitive skills and preferences, including
patience and identity, are malleable in adults, and that investments in
them reduce crime and violence. We recruited criminally engaged men
and randomized one-half to eight weeks of cognitive behavioral therapy
designed to foster self-regulation, patience, and a noncriminal identity
and lifestyle. We also randomized $200 grants. Cash alone and therapy
alone initially reduced crime and violence, but effects dissipated over
time. When cash followed therapy, crime and violence decreased
dramatically for at least a year. We hypothesize that cash reinforced
therapy’s impacts by prolonging learning-by-doing, lifestyle changes,
and self-investment. (JEL D12, D83, H23, I32, K42, O15, O17)
In many countries, poor young men exhibit high rates of violence, crime, and
other antisocial behaviors. In addition to their direct costs, crime and instability
hinder economic growth by reducing investment or diverting productive resources
to security. In fragile states, such men are also targets for mobilization into election
intimidation, rioting, and rebellion.1
1For example, poor urban young men were recently recruited into election violence in Sierra Leone (Christensen
and Utas 2008) and as mercenaries in Côte d’Ivoire (Blattman and Annan 2016).
*Blattman: Pearson Institute for the Study and Resolution of Global Conflicts and Harris School of Public
Policy, University of Chicago, 1155 E. 60th Street, Chicago, IL 60637 (e-mail: <PRESIDIO_ANONYMIZED_EMAIL_ADDRESS>); Jamison:
The World Bank Global Insights Initiative, MC4-404, 1818 H Street NW, Washington, DC 20433 (e-mail: julison@
gmail.com); Sheridan: Clinical Psychology, University of North Carolina at Chapel Hill, 235 E. Cameron Street,
Office 248, Chapel Hill, NC 27599 (e-mail: <PRESIDIO_ANONYMIZED_EMAIL_ADDRESS>). For implementation we thank Global
Communities and the Network for Empowerment and Progressive Initiatives (NEPI). For comments we thank
Thomas Abt, Jeannie Annan, Alex Coppock, Patricio Dalton, Stefano DellaVigna, Ruben Enikolopov, Roland Fryer,
Don Green, Jonas Hjort, Macartan Humphreys, Dean Karlan, Larry Katz, Shamus Khan, Winston Lin, Jens Ludwig,
Mattias Lundberg, Sendhil Mullainathan, Anandi Mani, Chris Muller, Suresh Naidu, Jonathan Pinckney, Vincent
Pons, Nancy Qian, Steve Radelet, Gautam Rao, Adam Reich, Alix Rule, Cyrus Samii, Rachel Strohm, Francesco
Trebbi, Eric Verhoogen, the referees, and participants at numerous conferences and seminars. This study was
funded by the National Science Foundation (SES-1317506), the World Bank’s Learning on Gender and Conflict in
Africa (LOGiCA) trust fund, the World Bank’s Italian Children and Youth (CHYAO) trust fund, the UK Department
for International Development (DFID) via the Institute for the Study of Labor (IZA), a Vanguard Charitable Trust,
the American People through the United States Agency for International Developments (USAID) DCHA/CMM
office, and the Robert Wood Johnson Health and Society Scholars Program at Harvard University (Cohort 5). The
contents of this study are the responsibility of authors and do not necessarily reflect the views of their employers,
funding agencies, or governments. Emma Tsui trained our qualitative researchers. Philip Blue, Natalie Carlson,
Samantha DeMartino, Camelia Dureng, Mathilde Emeriau, Yuequan Guo, Brittany Hill, Tricia Koroknay-Palicz,
Rebecca Littman, Ryan Luby, Ben Morse, Richard Peck, Patryk Perkowski, Colombine Peze-Heidsieck, Katherine
Rodrigues, Carmel Salhi, Joe St. Clair, Helen Smith, Gwendolyn Taylor, Abel Welwean, Prince Williams, Xing
Xia, Adam Xu, and John Zayzay provided research assistance through Innovations for Poverty Action. The authors
declare that they have no relevant or material financial interests that relate to the research described in this paper.
†Go to https://doi.org/10.1257/aer.20150503 to visit the article page for additional materials and author
disclosure statement(s).1166 THE AMERICAN ECONOMIC REVIEW april 2017
Two of the most common government responses are policing and job creation. Both
take the person as they are and try to change their incentives or simply incarcerate them
(Becker 1968; Draca and Machin 2015). This paper investigates an alternative: rehabilitation, or changing behavior by shaping people’s underlying skills and preferences.
A large literature has shown that a broad set of so-called noncognitive skills,
especially self-control, predict long-run economic performance and criminal activity.2 These skills respond to investment, especially in childhood (Cunha, Heckman,
and Schennach 2010). They are fostered by family, schools, and communities. There
is little evidence, however, on the returns to late-stage noncognitive investments,
and so it is unclear whether by adulthood self-investment or interventions can shape
noncognitive skills and hence behavior (Heckman and Kautz 2014; Hill et al. 2011).
It is also unclear what specific skills are both important and malleable.
To investigate, we recruited 999 of the highest-risk men in Liberia’s capital, generally aged 18 to 35. Most were engaged in part-time theft and drug dealing, and regularly had violent confrontations with each other, community members, and police.
We experimentally ran two interventions. One was an eight-week program of
group cognitive behavior therapy (CBT) called the STYL program (Sustainable
Transformation of Youth in Liberia). We assigned offers by lottery. Following this,
we held a second lottery for a $200 grant, about three months’ wages. The cash was
partly a measurement tool, to see if therapy affected economic decisions. The cash
was also a treatment, in the sense that it could stimulate legal self-employment,
and we included it to compare therapy to a rise in the returns to legal work.3
Experimentally, subjects either received offers of therapy alone, cash, therapy then
cash, or neither. To deliver both treatments cost about $530 per person.
CBT is a therapeutic approach that can be used to treat a range of harmful beliefs
and behaviors, including depression, anger, and impulsivity. First, CBT tries to
make people aware of and challenge harmful, automatic patterns of thinking or
behavior. Second, it tries to disrupt these patterns of thinking and to foster better ones by having people practice new skills and behaviors—learning by doing.
A Liberian nonprofit, the Network for Empowerment and Progressive Initiatives
(NEPI), designed and ran STYL. NEPI facilitators were themselves ex-combatants
or ex-criminals who graduated from prior NEPI programs.
Among noncognitive skills, NEPI designed STYL to focus on forward-looking
behavior and self-control. By self-control, psychologists and criminologists typically mean one’s short-term abilities to regulate emotions and to be resistant to
impulse, as well as more sustained abilities to be planful, persevering, and patient.
This concept has parallels to economic time preferences, and we measure them
in the manner of both fields. Becoming more self-controlled and forward-looking
are central components of many programs, from preschool to rehabilitation therapy.4 The curriculum focused on helping men foster skills of planning, goal-setting,
reflection, deliberate decision-making, and controlling emotions and impulses.
2For example, Nagin and Pogarsky (2004); Heckman, Stixrud, and Urzua (2006); Borghans et al. (2008).
3Evidence from East Africa suggests that the poor and unemployed are credit-constrained and have high returns
to cash (Haushofer and Shapiro 2016; Blattman, Fiala, and Martinez 2014; Blattman et al. 2016).
4For example, Gottfredson and Hirschi (1990) and Borghans et al. (2008). As an example of an intervention,
the famous Perry Preschool Program emphasized the ability of young children to plan tasks, to execute their plans,
and to review their work in social groups (Almlund et al. 2011).VOL. 107 NO. 4 BLATTMAN ET AL.: REDUCING CRIME AND VIOLENCE 1167
The therapy also encouraged nonviolent, noncriminal behavior and lifestyles by
fostering a change in the men’s social identity. A premise of STYL was that the men
self-identified as outcasts and did not hold themselves to the standards of mainstream
society. The therapy tried to persuade the men that they could change who they were
and how they were perceived. NEPI facilitators modeled this identity change. They
walked the men through basic steps, such as changing their appearance, engaging
in normal social interactions, and behaving more cooperatively. They discouraged
drug use and association with bad peers. Therapy also required men to practice
going to supermarkets, banks, and other “normal” places.
Research in both psychology and economics supports the idea that social identity
and associated values influence behavior, and that both can change. This literature
treats values as direct utility benefits or penalties from acting in accordance with
or against a set of preferences (Bénabou and Tirole 2004; Almlund et al. 2011).
Akerlof and Kranton (2000) and Jolls, Sunstein, and Thaler (1998) both argue that
these preferences or values are tied to a person’s social identity, and that to some
extent people can change their perceived social category and with it values that
reward and penalize certain behaviors.
There are striking parallels between STYL and socialization into militaries, street
culture, gangs, and armed groups. Such groups use similar techniques (appearance
change, practice, modeling) to shape young men’s social identity and behavior
(Vigil 2003; Wood 2008; Maruna and Roy 2007). NEPI designed STYL to reverse
this process.
We surveyed the men beforehand, a few weeks after the interventions, and a
year later. Most had no fixed address, phone, or even name. Despite this mobility,
we reinterviewed 92.4 percent. We rely on self-reported data since (like most poor
and fragile states) there are no administrative data. We did not necessarily trust
self-reports, and so we attempted to recheck and validate behaviors such as stealing
through in-depth interviews with a subsample.
We approached roughly 1,500 high-risk men, and 999 agreed to enter the study.
Of those assigned to therapy, nearly all attended at least one day, and two-thirds
completed it. The higher-risk men were the most likely to finish.
Men who received therapy reduced their antisocial behaviors dramatically,
roughly 0.2 standard deviations compared to the control group. Within a few weeks
of therapy, for example, we observe large reductions in an index of behaviors,
including stealing and drug selling. With therapy alone, these effects diminished
after a year. When therapy was followed by cash, however, the reductions in an
index of all antisocial behaviors were lasting.
The therapy probably worked through many channels, and we see evidence of
improvement in two of the hypothesized channels: time preferences and noncriminal
identity/values, with time preference changes most persistent. There is also some evidence of improvements in positive self-regard, plus temporary changes in drug abuse
and noncriminal social networks. With therapy alone, a broad index of all these intermediary outcomes changes diminished after a year, just as we saw with antisocial behavior itself. When therapy was followed by cash, however, the overall changes in these
intermediary outcomes were lasting and fairly large: at least 0.25 standard deviations. If
we account for multiple comparisons, it becomes difficult to single out any one mechanism, but the largest and most statistically significant change is in time preferences.1168 THE AMERICAN ECONOMIC REVIEW april 2017
How was cash used? Regardless of therapy, little of the grant was spent on drugs
or “wasteful” things. Most funds were invested in business or saved. Cash led to a
short-term increase in an index of economic performance (including income, savings, employment, and investment), due largely to increased petty trading. After a
year, however, these gains disappeared, partly because most men were robbed regularly, irrespective of treatment.
The fact that the grant was crucial to sustaining therapy’s effects is our most
unexpected and important finding. As we find no sustained effect of cash on earnings, cash clearly did not raise the opportunity cost of antisocial behavior after a
year. Thus, economic performance does not explain the sustained effect of therapy
plus cash on crime and aggression. Drawing on qualitative interviews and psychological theory, we suggest that the short-term increase in income and legal employment helped to solidify therapy’s impact on noncognitive skills and preferences.
Specifically, for a few months after therapy, cash allowed men to project a new self,
to stave off homelessness and stealing, and practice the self-control and future orientation started by therapy. This hypothesis will be important to test in future research.
An obvious concern is our reliance on self-reported data. We argue that misreporting is unlikely to drive our results for two reasons. The first is the pattern of
treatment effects: 12–13-month impacts from therapy plus cash, but not from cash
or therapy only. Systematic measurement error would need to be correlated with
the “both” treatment arm only. This seems feasible but unlikely, especially given
the magnitudes of the impacts. To check further, we attempted to validate a subset of questions using intensive qualitative observation. The patterns suggest that,
if anything, the control group underreported sensitive behaviors such as stealing.
Hence, the treatment effects may actually underestimate therapy’s impacts. We also
learn that the control group reported fewer expenditures in the survey versus the
validation exercise, suggesting that some of the short-term economic gains from
cash may be illusory. These insights come with the caveat that they assume that data
collected though in depth interviews on a small subset of questions, with a focus on
trust-building, are more accurate than survey measures. It is better to think of the
validation as a confidence-building exercise rather than hard proof.
In addition to evaluating the pairing of an economic intervention with CBT, this
study addresses several gaps in the literature. One is the absence of evidence on behavior change outside the United States, especially in fragile states. Even within the United
States, however, there is limited evidence on adult behavior change. Most evaluations
of US-based crime and violence-reduction programs focus on education and employment interventions.5 Studies of CBT tend to be small-sample and nonexperimental
(Wilson, Bouffard, and Mackenzie 2005).6 But STYL’s impacts on adult antisocial
behavior are consistent with evidence from US adolescents and children, which show
that CBT programs in schools and correctional institutes reduce criminal recidivism.7
5Two US programs, Job Corps and ChalleNGe, are residential programs for at-risk youth that tackle noncognitive skills but focus on jobs and job training (Schochet, Burghardt, and McConnell 2008; Millenky et al. 2012).
6An exception is Little, Robinson, and Burnette (1994), who randomly assigned CBT to 1,381 general offenders in Tennessee. They found that re-arrest fell from 56 percent to 41 percent after five years. Our study adds to this
large-sample evidence.
7For evidence on children and adolescents, see Heckman and Kautz (2014) and Hill et al. (2011). Metaanalyses of adolescent and adult interventions in correctional institutes find that CBT-informed programs appear to
outperform alternate therapies (Andrews et al. 1990; Lipsey 2009).VOL. 107 NO. 4 BLATTMAN ET AL.: REDUCING CRIME AND VIOLENCE 1169
Finally, few studies have measured noncognitive skill and preference changes