The Role of Theory in Experimental Design: Experiments Without Randomization

Some who have written about the logic of experimentation arguethat random assignment of subjects to treatment conditions isan essential attribute of an experiment. Others disagree. Ratherthan treating this as a matter of dueling definitions, we considerexperiments without randomization from a theoretical perspective.Our central contention here is that, for some research questions,theory dictates systematic (not random) assignment of respondentsto experimental conditions. Two such areas of inquiry are researchon political tolerance and on institutional legitimacy. Thisarticle gives cursory attention to the former body of work anddetailed attention to the latter, based on an experiment conductedin a survey in 2001 on the consequences of the American presidentialelection for institutional legitimacy. Because in both instancestheory requires nonrandom assignment, the problem becomes oneof identifying the costs of nonrandomization (threats to internalvalidity) and specifying analytical techniques that might amelioratethose costs. Consequently, we present results from a statisticalapproach that addresses the problem of nonrandomization. Themost important claim of this article is that theory ought tospecify research design, including experimental designs, andthat dogmatic attachment to one definition of experiment willnot serve the discipline of political science.     

Stressful life events and adolescent drug use: Moderating influences of the MAOA gene

Purpose

Though stressful life events appear to impact the likelihood and frequency of substance use among adolescents, these effects are often varied and inconsistent. We suggest that the polymorphic MAOA gene may be partially responsible for variable susceptibility to environmental pressures and substance use. More specifically, we hypothesize that adolescents possessing low activity alleles for the MAOA genotype are more likely to respond to stressful life experiences by initiating substance use.

Methods

The genetic subsample of the National Longitudinal Study of Adolescent Health was analyzed (2,574 adolescents) using logistic regression models for each gender. Respondents’ self-reports of eight key stressors were used to create a composite life stress scale which was allowed to interact with a variable that represented the number of low activity MAOA alleles.

Results

For males, a significant interaction emerged between stressful life experiences and the MAOA gene for alcohol (p = .029) and marijuana (p = .039) initiation. For females, the interaction was not significant in each model.

Conclusions

MAOA interacts with life stress to increase the likelihood of substance use initiation for males. Those with a low activity MAOA allele are more likely to initiate substance use than those with a high activity allele when exposed to stressful experiences.     

Making Short Politics Placements Work

Short placements can provide an important and meaningful experience of politics in action for students who are unable to benefit from the generally lengthy placements currently on offer. This article is based on the findings of the three-year HEFCE-funded project The Scholarship of Engagement for Politics and explores the potential of short, local, research-based placements, which are embedded in modules, supported by online journaling and effectively assessed, to enrich students' understanding of politics and enhance their employability.     

False advertising and experience goods: the case of political services in the U.S. senate

This study uses the voter-shopping construct to analyze signaling of moderateness in the U.S. Senate. We compare legislator-provided signals (advertising)—such as membership in the U.S. Senate’s Centrist Coalition—with actual voting histories in order to characterize these types of advertising cues as sincere or insincere. Following recent research indicating that moderate legislators receive greater financial support, we test whether or not Political Action Committees (PACs) are willing to support financially those who send false signals of moderateness. Our results show that the mean level of real PAC contributions garnered by non-moderate Democrats who send false signals exceeds that of the non-moderate Democrats who do not do so by $182,078. This figure is about 74% of mean level of real PAC contributions for those non-moderate Democrats who do not send false signals.     

Confirmation Politics and The Legitimacy of the U.S. Supreme Court: Institutional Loyalty, Positivity Bias, and the Alito Nomination

Gibson, Caldeira, and Spence (2003a, 2003b, 2005) expound the theory of positivity bias in their analysis of the legitimacy of the U.S. Supreme Court in the aftermath of Bush v. Gore. This theory asserts that preexisting institutional loyalty shapes perceptions of and judgments about court decisions and events. In this article, we use the theory of positivity bias to investigate the preferences of Americans regarding the confirmation of Judge Samuel Alito as an associate justice of the Supreme Court. More specifically, from the theory of positivity bias, we derive the hypothesis that preferences on the Alito confirmation are shaped by anterior commitments to the Supreme Court. Based on an analysis of a national panel survey, we find that those who have a high level of loyalty toward the Supreme Court rely much more heavily on what we term judiciousness—in contrast to ideology, policy, and partisanship—in forming their opinions on whether to confirm Alito. Thus, institutional loyalty provides a decisive frame through which Americans view the activity of their Supreme Court.