Heterogeneity in moderation effects: How willingness-to-pay shapes the knowledge-behavior relationship in sustainable...

The persistent perceived knowledge-behavior gap in sustainable consumption, where heightened consumer awareness often fails to translate into sustainable purchases, presents a major challenge. While recent research suggests that economic factors, specifically Willingness-to-Pay (WTP), may moderate this relationship, it remains unclear if this moderation effect varies systematically across consumer segments. This study aims to investigate WTP's moderating role, identify whether consumers naturally segment based on distinct moderation patterns, and examine the psychological predictors of segment membership. Using survey data from 500 consumers, we first estimate a moderation model examining the interaction between perceived knowledge and willingness-to-pay. We then explore heterogeneity in this moderation effect using a segmentation approach based on psychological attributes. Results confirmed that WTP significantly and negatively moderates the perceived knowledge-behavior link (β = -1.56, p < 0.001), a finding robust to censoring correction. Three distinct consumer segments emerged: Price-Sensitive, Value-Driven, and Premium-Oriented, which demonstrated substantial differences in sustainable purchasing behavior. Due to a ceiling effect in the purchase behavior measure (17.4% of respondents scored at the maximum), sensitivity analyses excluding these cases were conducted to verify cluster stability and enable proper within-segment moderation estimation. These analyses confirmed that the cluster structure remained stable (Adjusted Rand Index = 0.89). A three-way interaction model (Knowledge × WTP × Segment) confirmed that moderation strength differed significantly across segments (p < 0.01). The moderating effect of WTP varied systematically: strongest among Price-Sensitive consumers (β = -1.01, p < 0.001), moderate among Value-Driven consumers (β = -0.60, p < 0.01), and weakest but still significant among Premium-Oriented consumers (β = -0.78, p < 0.01). This pattern provides direct evidence of moderation heterogeneity. Demographic variables alone poorly predicted segment membership (43.3% accuracy, marginally above the chance level of 36.4%), confirming that the segments reflect psychological rather than demographic differences. This research highlights the conditional nature of the perceived knowledge-behavior relationship, demonstrating that the behavioral relevance of sustainability knowledge depends on consumers' economic commitment. By revealing systematic heterogeneity in how willingness-to-pay moderates this relationship across consumer segments, the study reconceptualizes the knowledge-behavior gap as a structurally conditioned phenomenon and provides a mechanism-based segmentation framework for more targeted sustainable marketing strategies.