The Top-down Influence On Length Perception Of Curves Induced By Object-based Representation

As an indispensable function of visual system, object recognition has been attracted to cognitive psychology, computer science and neuroscience. It was pervasively considered that low-level information played a determinative role on perceptual representation. Taking the perspective of interaction between global and local information, this study reconsidered the relationship between object configuration and its local features:especially top-down influence on the perception of low-level information.Four experiments were designed to explore how object-based representation influences curve length perception. All the curves were digitalized from natural curves. In all experiments, subjects were asked to adjust the length of a straight line till its length equals to the target curve’s length. Target curves were set in three different contexts:subjects observed the inner or outer edge of a crescent (Experiment1), the inner or outer edge of the contour of a crescent (Experiment2), or two separate curves with different lengths (Experiment3). To exclude differentiation caused by sample difference, all three tasks were required in Experiment4.The main findings were as follows:(1) Under crescent and contour condition, curve was perceived shorter as outer edge than as inner edge;(2) Under separate curves condition, curve was perceived shorter when itself was the shorter one than when it was the longer one, which appeared as a contrast effect.The results showed that object-based representation affected length perception of curves. This influence even overwhelmed the contrast effect emerging in separate curves task. We can infer that relationship between low-level information and object-based representation was not a one-way process. There also existed involuntary influence on low-level feature perception through a top-down way.