Purpose: The rapid growth of information technology and the expansion of digital tools have fundamentally transformed consumption patterns and purchasing behavior, making online shopping one of the primary modes of exchange. Consumers can easily access product information, compare prices, and review feedback from others, enabling more informed decision-making. In this context, social media serves as a dynamic platform for shaping consumer attitudes and purchase intentions, and influencer marketing has emerged as a key digital marketing tool. Influencers, through authentic content creation and close engagement with audiences, significantly affect purchasing tendencies, and their credible endorsements increase purchase likelihood. However, the effectiveness of influencer marketing is not consistent and is strongly influenced by contextual factors, particularly extrinsic motivations such as discounts and rewards. Despite this, existing studies have rarely examined influencer marketing and extrinsic incentives simultaneously within motivational frameworks, particularly Self-Determination Theory. Accordingly, the present study aims to investigate the effect of influencer marketing on online purchase behavior, considering the moderating role of extrinsic motivation within a quasi-experimental design.
Method: This study employed a quantitative and applied approach using a quasi-experimental design to examine causal relationships under real-world conditions. The statistical population included women aged 22–40 active on Instagram with online shopping experience and familiarity with fashion influencers. A total of 232 valid responses were collected through purposive sampling, meeting the requirements of structural equation modeling and quasi-experimental design. Data were gathered via an online questionnaire distributed through social media platforms. Participants were assigned to four groups, including three experimental groups and one control group: (1) influencer video with discount, (2) influencer video without discount, (3) brand promotional content with discount, and (4) control group with no intervention. The fashion brand “Serge” and influencer “Yasmina Style” were used as experimental stimuli.
Findings: Among the 232 female respondents, most were single (75%) and aged 22–27 (59%). Additionally, 44% held postgraduate degrees and 44% were employed. About 51% reported purchasing clothing five or more times per year, indicating high engagement in online shopping, while 71% followed fashion influencers. The analysis revealed that the “influencer + discount” group showed the highest levels of purchase intention and actual purchasing behavior. The findings indicate that influencer marketing has a significant positive effect on online purchasing behavior, and extrinsic motivation significantly strengthens this relationship. However, the direct effect of extrinsic motivation alone on online purchasing behavior was not significant, suggesting that such incentives cannot independently trigger purchase behavior.
Conclusion: This quasi-experimental study provides empirical evidence that influencer marketing plays a crucial role in stimulating online purchasing behavior, while extrinsic motivation acts as a reinforcing factor. The results indicate that influencer credibility and content form the foundation of consumer attitudes, but external incentives are necessary for translating purchase intention into actual behavior. From a theoretical perspective, the study applies the Theory of Planned Behavior within a quasi-experimental framework to explain causal relationships between social influence and financial incentives in digital environments. From a practical perspective, marketers are advised to strategically select influencers and integrate extrinsic incentives such as discounts into campaigns. The findings demonstrate that combining influencer marketing with financial incentives can significantly enhance conversion rates and digital marketing effectiveness.