Cognitive Contours

@article{Gregory1972CognitiveC,
  title={Cognitive Contours},
  author={RICHARD L. Gregory},
  journal={Nature},
  year={1972},
  volume={238},
  pages={51-52}
}
IT is surprisingly easy to devise simple line figures which evoke marked illusory contours. Unlike the well known brightness contrast effects, these illusory contours can occur in regions far removed from regions of physical intensity difference; and they can be orientated at any angle to physically present contours. Fig. 1 is the figure described by Kanizsa1. An illusory triangle is observed whose apices are determined by the blank sectors of the three disks. The “created” object appears to… 
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Vivid and perceptually salient subjective contours are perceived when inducing (two-dimensional) objects that move and change form so as to "simulate" the presence of an occluding shape are defined
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The errors in aligning a dot with an illusory contour seem to be related to the asymmetrical shape of the single objects, which are able to induce an illused contour, as well as figure-ground segregation.
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It was found that apparent brightness is influenced more by number of inducing elements, whereas apparent sharpness increases more with inducing element width, and stimulus configuration may influence brightness and sharpness differentially.
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