Experimental criminology is an important area of research and scholarship and is closely linked with the evidence-based movement in social policy. Its profile has been elevated in recent years with any number of new scholarly and policy-oriented developments, methodological advancements, and a rapidly expanding body of experimental studies. Experimental methods have deep roots in criminology and the social and behavioral sciences more generally. These can be found in the study of criminal activities, development and testing of criminological theories, and evaluations of programs and policies to reduce crime. Experiments take place in varied field settings as well as in laboratories and are a rich source of scientific knowledge that has helped to advance the field of criminology and public policy. This book sets out to recapture the full breadth of experimental criminology and report on new and innovative contributions that it is making to basic scientific knowledge and more effective public policy.

The idea for this book originated with an international workshop that was organized and hosted by the Netherlands Institute for the Study of Crime and Law Enforcement (NSCR). Held in Amsterdam on May 9–10, 2011, the NSCR workshop brought together leading scholars and experimentalists from North America and Europe to report on and debate new findings and methodological developments in experimental criminology. Papers were commissioned from the authors and presented at the workshop. Each presentation was followed by a detailed critique from an assigned discussant and discussion among participants. After the workshop, authors submitted revised versions of their papers. Finally, we commenced two rounds of reviewing and editing, and papers were accepted for inclusion in the volume.

INTRODUCTION

Experimental criminology is a part of a larger and increasingly expanding evidence-based movement in social policy. The evidence-based movement first began in medicine and has, more recently, been embraced by the social sciences. Evidence-based social policy advocates – in areas such as education, poverty reduction, and crime prevention – are dedicated to increasing the use of scientific evidence in the implementation of government programs so critical social problems can be addressed without wasting scarce taxpayer funds. Experimental criminologists, and organizations such as the Academy of Experimental Criminology and the Campbell Collaboration’s Crime and Justice Group, have been leading advocates for the advancement of evidence-based crime control policy in general and the use of randomized experiments in crime and justice research in particular.

Experimental criminology has, for the most part, moved past the first wave of criticism that questioned the use of randomized controlled trials (RCTs) in crime and justice evaluations. Two key concerns were that (1) it was not ethical to randomize treatments, interventions, or programs in crime and justice; and (2) randomized experiments could not be implemented in the real world (Clarke and Cornish 1972; Esbensen 1991; Erez 1986; Geis 1967). As Weisburd (2010) recently argued, the growth of criminological experiments in a broad range of real-world settings that have been carried out in an ethical manner demonstrates that these concerns are, in most cases, based in folklore rather than facts. However, as the influence of randomized experiments in crime and justice has grown in recent years, a second wave of criticism has been increasingly articulated by criminologists concerned by the field’s experimental turn. These critiques share a common concern that experimental criminology blindly advocates the superiority of RCTs over quasi-experiments and observational studies.

INTRODUCTION

Experimenting with crime and social programs has a rich tradition. Some notable developments include the “lost letter” experiments of the 1970s (Farrington 1979) and the experimenting society concept advanced by Donald Campbell and others during the 1960s and 1970s (see Campbell 1969, 1979). Researchers used the lost letter experiments, which involved leaving cash in an apparently lost letter on the street, and other similar techniques to examine public dishonesty and minor deviance. The experimenting society concept is rooted in the large-scale social programs of the Kennedy and Johnson administrations and the need to identify valid and rigorous methods of evaluation. It has generated profound interest in the use of experiments to test the impact of criminological interventions.

Present-day experimental criminology very much has its roots in these developments (Sherman 2010). At its heart are the methods of experimentation introduced in science in the seventeenth century. The defining feature of an experiment is control of the independent variable. An experiment is designed to test a causal hypothesis about the effect of variations in one variable on variations in another. A hypothesis cannot be tested experimentally unless it can be expressed in these terms. The methodological adequacy of any test of a causal hypothesis can be assessed on four major criteria (Campbell and Stanley 1966; Cook and Campbell 1979; Shadish, Cook, and Campbell 2002). Statistical conclusion validity refers to whether the two variables of interest truly are related. Internal validity refers to whether a change in one variable did produce a change in another. Construct validity refers to the theoretical constructs that underlie the measured variables; and external validity refers to how far the results can be generalized to different persons, settings, and times.