title: The perception of closed flat knots and completion by folding.
abstract: The aim of the present research was to study a well-defined set of line drawings that have never been analyzed before, and that are perceived as closed flat knots (CFKs). These knots are obtained by folding two-dimensional laminae. From this study it emerged that the perception of CFKs is always accompanied by a type of amodal completion, which had not previously been studied, and which we have called "completion by folding". It occurs when three quadrilaterals are so arranged that they look like a sheet of paper folded around one of them, partly occluded and partly occluding. Two experiments were carried out on this phenomenon revealing that a three-level stratification is produced in the completion by folding that facilitates unification between occluded figures, even when current models do not foresee such a perceptual solution, either because the distance between the two figures that become a unit is too big (experiment ) or because the slope between the two figures is not favorable (experiment 2). A third experiment, which took up the problem of the perception of CFKs, revealed the following: (1) Besides the prototype CFK, obtained by the interlacing of a rectangular lamina, there is a theoretically infinite class of CFKs. (2) The drawing of all the possible closed flat knots involves geometrically precise rules. (3) Not all feasible knots with these rules are seen as such. (4) Only the knots with characteristics of alignment and regularity are recognized as knots. (5) The closed flat knots are seen as the result of a transformation which the figure undergoes. This evidence constitutes a remarkable perceptual problem, discussed with reference to the recent theories of amodal completion.
authors: Dipartimento di Psicologia e Antropologia Culturale, Università di Verona, Italy. mmassironi@univr.it
authors: Manfredo
authors: M
authors: Massironi
authors: Daniela
authors: D
authors: Bressanelli
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008297:Male; D010466:Perceptual Closure / Q000502:physiology*; D011340:Problem Solving; D013334:Students / Q000523:psychology; D014796:Visual Perception / Q000502:physiology*