Amodal completion of boundaries in coloured surfaces

We present an experimental study on the influence of colour and spatial position in the assessment of boundaries in occluded surfaces. Subjects were asked to mark the place that they judged to be the location of a boundary between two differently coloured parts of a vertical rectangle partially occluded by a horizontal rectangle. Besides the use of eight pairs of colours, the position of the occluder was randomly changed resulting in 13 possible sizes of the coloured parts. The same colours were set for half of the time on the lower part of the vertical rectangle, and for half on the upper part, so as to verify whether changing the colour location would give rise to measurable effects. Results show that amodal completion is influenced not only by spatial cues but also by colour.