Abstract
This article has two primary objectives: (i) to replicate an agent-based model of social interaction by Bhavnani (2003), in which the author explicitly specifies mechanisms underpinning Robert Putnam's (1993) work on Civic Traditions in Modern Italy, bridging the gap between the study's historical starting pointopolitical regimes that characterized 14th Century Italy - and contemporary levels of social capital - reflected in a 'civic' North and an 'un-civic' South; and (ii) to extend the original analysis, using a landscape of Italy that accounts for population density. The replication exercise is performed by different authors using an entirely distinct ABM toolkit (PS-I) with its own rule set governing agent-interaction and cultural change. The extension, which more closely approximates a docking exercise, utilizes equal area cartograms otherwise known as density-equalizing maps (Gastner and Newman 2004) to resize the territory according to 1993 population estimates. Our results indicate that: (i) using the criterion of distributional equivalence, we experience mixed success in replicating the original model given our inability to restrict the selection of partners to 'eligible' neighbors and limit the number of agent interactions in a timestep; (ii) increasing the number of agents and introducing more realistic population distributions in our extension of the replication model increases distributional equivalence; (iii) using the weaker criteria of relational alignment, both the replication model and its extension capture the basic relationship between institutional effectiveness and civic change, the effect of open boundaries, historical shocks, and path dependence; and (iv) that replication and docking may be usefully combined in model-to-model analysis, with an eye towards verification, reimplementation, and alignment.
Highlights
1.1 In his seminal book entitled Making Democracy Work, Robert Putnam advances a controversial hypothesis: "[that] ... social patterns, plainly traceable from early medieval to present day Italy turn out to be decisive in explaining why, on the verge of the twenty-first century, some communities are better able than others to manage collective life and sustain effective institutions" (Putnam 1993, p. 121)
Putnam's work is missing what Margaret Levi (1996, p. 46) refers to as mechanisms for the "production, maintenance, and growth of social capital"-mechanisms to link the historical social context, namely political regimes that characterized 14th Century Italy, with the present social order-leaving the reader to infer how "civic" and "uncivic" communities in contemporary Italy emerged from their historical starting points.[1]
By analyzing how different institutions interact with heterogeneous individuals, the analysis provides additional insight into why contemporary Italy is characterized by a civic North and an un-civic South
Summary
1.1 In his seminal book entitled Making Democracy Work , Robert Putnam advances a controversial hypothesis: "[that] ... social patterns, plainly traceable from early medieval to present day Italy turn out to be decisive in explaining why, on the verge of the twenty-first century, some communities are better able than others to manage collective life and sustain effective institutions" (Putnam 1993, p. 121). 1.5 In reviewing the state of the art in model-to-model analysis, Wilensky and Rand ( 2007) parse the literature into "ambitious" attempts at docking (i.e. the alignment of models developed for different purposes to demonstrate their capacity to produce similar results) and replications (i.e. the re-implementation of an original model) Included in their list of docking exercises are Axtell, Axelrod, Epstein and Cohen's (1996) attempt to "dock" different simulation models, Grimm et al.'s ( 2005) demonstration that models constrained by dissimilar theories can generate similar patterns, Bigbee, Cioffi-Revilla, and Luke's (2005) implementation of the Epstein and Axtell Sugarscape model (1996) using MASON, as well as North and Macal's ( 2002) implementation of the beer game ( Forrester 1961) in Mathematica, Swarm, and Repast. Other notable efforts at replication in the Journal of Artificial Societies and Social Simulation alone include Izquierdo, Izquierdo, and Gotts ( 2008) replication of Macy and Flache's ( 2002) work on the dynamics of reinforcement learning, Oliver Will and Rainer Hegselmann's (2008) and Will's (2009) attempts to replicate Macy and Sato's (2002) model addressing the issues of trust, cooperation and market formation, as well as Merlone, Sonnessa and Terna's ( 2008) use of different implementation approaches and multiple modeling implementations to highlight both the intricacies and advantages of replication
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