Table 2.

Overview of methods used to research behavioral spillover: examples from environmental behavior.

Methodological approach	Data collection and analysis methods	Examples from environmental behavior	Strengths	Weaknesses
Qualitative	• Interviews or open-ended survey questions	Austin et al., 2011; Boström et al., 2015; Nash et al., 2019; Uzzell and Räthzel, 2018	• Expose unexpected spillovers	• Risk of presentational bias
	• Thematic, content, discourse (or similar) analysis		• Shed light on spillover mechanisms, drivers and barriers	• Partial or selective recollection • No measurement standardization
	• Self-reports or other (e.g., practitioner) accounts
	• Biographical (retrospective) or evaluative (during/immediately after intervention)
Quantitative (cross-sectional)	• Survey, card sort or secondary data analysis (e.g., retail data)	Thøgersen, 1999; Barr et al., 2010; Whitmarsh and O’Neill, 2010; Austin et al., 2011; Gabe-Thomas et al., 2016	• Quantify strength of relationships between measured behaviors	• No causal relationships identified
	• Cluster or factor analysis		• Measurement standardization	• Limited to expected spillovers
	• Correlational analysis
	• Regression analysis
Quantitative (longitudinal)	• Surveys at 2+ timepoints	Thøgersen and Noblet, 2012; Kaida and Kaida, 2015; Poortinga et al., 2013; Thomas et al., 2016.	• Quantify strength of relationships between measured behaviors	• No causal relationships identified
	• Repeated measures analysis or multi-level modeling		• Measurement standardization	• Limited to expected spillovers
	• Correlational analysis
	• Regression analysis (including time series, panel data, and difference-in-difference models)
Quantitative (experimental)	• Online, laboratory, or field experiments	Van der Werff et al., 2014a,b; Juhl et al., 2017.	• Causal relationships and mechanisms identified	• Limited to expected spillovers
	• Self-reported or observed behavior		• Measurement standardization
	• Randomization to behavioral intervention
	• Analysis of variance
	• Regression analysis
Mixed-methods	• Combination of qualitative and quantitative methods (e.g., experiment and interviews)	Verfuerth, in preparation; Lede, in preparation.	As above	As above