Dissecting the effects of adaptive encoding and predictive inference on a single perceptual estimation

The human visual system exploits continuity in the visual environment, which induces two contrasting perceptual phenomena: repulsive aftereffects and attractive serial dependences. Recent studies have theorized that these two effects concurrently arise in perceptual processing, but empirical evidence that directly supports this hypothesis lacks. Here we show that the two effects concurrently modulate estimation behavior in a typical sequence of perceptual tasks. We first demonstrate that observers estimation error as a function of both the previous stimulus and response cannot be fully described by either attractive or repulsive bias but is instead well captured by a summation of repulsion from the previous stimulus and attraction toward the previous response. We then reveal that the repulsive bias is centered on the observers sensory encoding of the previous stimulus, which is again repelled away from the preceding trials, whereas the attractive bias is centered precisely on the previous response, which is the observers best prediction about the incoming stimuli. Our findings provide strong evidence that sensory coding is shaped by dynamic tuning of the system to the past stimuli, inducing repulsive aftereffects, and followed by inference incorporating the prediction from the past estimation, leading to attractive serial dependence.