Structural factors in figure perception

In this report, we examine tachistoscopic perception of lines in structured figures. Previous research has shown that perception of lines is facilitated when the lines occur as parts of coherent three-dimensional figures. Experiment 1 demonstrates that it is not necessary for the figure to be three-dimensional to obtain facilitation. Experiments 2 and 3 show that three-dimensionality is not sufficient either. What is important is that the target lines be structurally relevant to the figure. However, structural relevance of a target segment to the figure as perceived with unlimited viewing time is not perfectly correlated with perceptibility under tachistoscopic conditions; it appears that the targets which fall on the external contour of a figure may be facilitated even without a high degree of structural relevance. In view of this, we suggest a model in which perceivers use processing heuristics to direct processing to aspects of the input that are potentially important for determining the structure of the final figure, working primarily from the outside in.