<p>The Bayesian framework conceptualizes human perception as a process of probabilistic inference, where the brain integrates prior expectations with incoming sensory evidence to construct a mental model of the world. Within this framework, several distinct theories—collectively termed the “simple Bayesian model”—suggest that perceptual atypicalities in autism stem from an imbalance between the precision of prior beliefs and sensory input. This study presents a systematic review and the first meta-analysis to evaluate empirical evidence for the simple Bayesian model. We synthesized 24 effect sizes from 23 eligible studies using a random-effects model to test its core predictions: that autistic individuals exhibit universally “broader” priors and/or heightened sensory precision compared to non-autistic controls. We found a significant, small-to-moderate overall effect in the predicted direction (Hedge’s <i>g</i> = 0.37). However, heterogeneity across studies was large and significant and was not explained by any of the examined moderators: prior type (structural vs. contextual), stimulus type (social vs. nonsocial), task setting (implicit vs. explicit), cognitive domain (higher-level cognition vs. perception), or participant characteristics. Given the significant unexplained heterogeneity, our findings offer only limited support for a universal “simple Bayesian model” of autism. We conclude that future research should move beyond the simple Bayesian model to investigate more sophisticated, hierarchical Bayesian accounts of autism.</p>