A systematic review and meta-analysis of trust in automated vehicles: The role of anthropomorphism

Trust is a critical factor in the acceptance and safe deployment of automated vehicles (AVs). In recent years, it has remained a prominent topic of discussion, with market data indicating that public trust in these technologies remains suboptimal. As a result, researchers have explored various strategies to enhance trust in AVs. One such strategy involves anthropomorphizing AVs in different modalities, such as adding human-like visual features or human voices. Initially, it was assumed that incorporating anthropomorphic features would enhance trust in AVs. This meta-analysis addresses the role of anthropomorphism in AV trust as a timely response to the ongoing debate. Following PRISMA guidelines, a total of 66 articles and 70 effect sizes from 5903 participants from seven databases were included in this meta-analysis.The results revealed that anthropomorphic interfaces, compared to non-anthropomorphic interfaces, do not significantly improve trust in AVs (Standardized Mean Difference (SMD) = 0.04, not significant). However, in general, adding auditory anthropomorphic features is recommended for increasing trust compared to visual anthropomorphic features (SMD: 0.30 vs. -0.48). Moreover, different levels of anthropomorphism (superficial vs. deep) did not have a significant impact on trust in AVs. The overall trend indicated that with increasing age of participants, the reliance on anthropomorphic interfaces for increasing trust became more pronounced.This meta-analysis shows that adding human-like features is not a dependable way to build trust in AVs. Future works are needed on how it can be compared to other approaches like explainability. Generally, as a suggestion for stakeholders, it is important to recognize that the impact of anthropomorphic interfaces on trust in AVs is not the same as assumptions.