 The study investigates how the centriperietal positivity, CPP, adapts to different environments that place different constraints on evidence accumulation, and shows that adaptations in evidence weighting are reflected in changes in the CPP. The CPP becomes more sensitive to fluctuations in sensory evidence when large shifts in evidence are less frequent, and is primarily sensitive to fluctuations in decision-relevant sensory input. A complementary trifasic component over occipitoperietal cortex encodes the sum of recently accumulated sensory evidence, and its magnitude covaries with parameters describing how different individuals integrate sensory evidence over time. A computational model based on leaky evidence accumulation suggests that these findings can be accounted for by a shift in decision threshold between different environments, which is also reflected in the magnitude of predecision EEG activity. The study reveals how adaptations in EEG responses reflect flexibility in evidence accumulation to the statistics of dynamic sensory environments.