Fake reviews and consumer decision dynamics: a mathematical modeling approach based on the Theory of Planned behavior in Indonesian e-Commerce

The rise of e-commerce in Indonesia has reshaped consumer purchasing behaviour, with online reviews serving as a vital form of social proof. However, this influence is increasingly undermined by the proliferation of fake reviews and deceptive feedback, which are designed to mislead consumers. In a landscape marked by uneven digital literacy and widespread online shopping, Indonesian consumers are particularly vulnerable to such manipulative content, which can lead to misguided decisions and diminished trust in e-commerce platforms. This study applies the Theory of Planned Behaviour (TPB) to examine how fake reviews affect consumer attitudes, subjective norms, and perceived behavioural control factors that collectively shape purchase intentions. To address the scarcity of quantitative models in this area, a fuzzy logic-based mathematical model is developed to capture the uncertainty in consumer perceptions and simulate decision-making processes. Data were collected from 250 active Indonesian e-commerce users via a structured questionnaire. The responses were converted into fuzzy membership values for each TPB component and analysed using fuzzy inference and defuzzification techniques. The simulation results reveal that exposure to fake reviews significantly reduces attitudes and subjective norms, thereby decreasing purchase intention even when perceived behavioural control remains high. This research offers both theoretical and methodological contributions by integrating TPB and fuzzy logic into a dynamic model of consumer behaviour under misinformation. The findings provide valuable insights for platform designers and policymakers to understand better, anticipate, and mitigate the impact of fake reviews on consumer trust and decision-making.