Abstract
Serial dependence, an effect in which the perception of a stimulus is biased towards recent percepts, has recently been demonstrated in a wide range of visual features (e.g. orientation, numerosity, facial identity, and attractiveness). This perceptual bias may counteract visual noise and uncertainty in object representations, and is thus believed to be adaptive, since real world objects are often much more stable than their constantly changing image properties. However, in cases where objects being perceived are not stable but undergoing a continuous change, is there a perceptual bias towards the recent past (sticky bias) or towards the expected change (predictive bias)? We studied this question by modifying an experimental paradigm used in previous studies demonstrating serial dependence for the perception of orientation. Subjects were asked to report the orientation of a sequence of arrows by matching a response bar. Instead of changing the orientation of the arrow randomly across trials, we rotated the arrow in a sometimes-predictable-sometimes-unexpected way. In the "predictable" trials (about 75%) the arrow was rotated by 16 degrees in a consistent direction from the previous trial inducing an expected continuous change. In the "unexpected" trials (about 25%, randomly interspersed among the "predictable" trials) the arrow was rotated either clockwise or anti-clockwise by 8 degrees. While a sticky bias would predict a perceptual pull toward the 1-back stimulus for "unexpected" trials, our results showed a perceptual pull towards the expected orientation for those trials, which suggests a contribution of predictive bias. This could not be explained by a simple response bias in the expected direction of rotation because such a response bias was not observed for the "predictable" trials. Our results suggest that serial dependence may also have a predictive component that facilitates the perception of continuous changes when they should be expected.
Meeting abstract presented at VSS 2017