A new Bayesian model of visual word recognition is used to simulate neighborhood frequency effects in lexical decision. These effects have been reported as being either facilitatory or inhibitory in behavioral experiments. Our model manages to simulate the apparently contradictory findings. Indeed, studying the dynamic time course of information accumulation in the model shows that effects are facilitatory early, and become inhibitory at later stages. The model provides new insights on the mechanisms at play and their dynamics, leading to better understand the experimental conditions that should yield a fa-cilitatory or an inhibitory neighborhood frequency effect.