Many experimental comparisons between real and anomalous contours have proven the functional equivalence of the two conditions; however, there are some contradictory findings. One of these is obtained by analyzing the anomalous contours in the light of a new illusion, called the ‘illusion of angularity’. A circle becomes a polygon when it covers the centre of a radial arrangement of black stripes, and a polygon changes its perceptual shape depending on its orientation with respect to the same radial arrangement. Phenomenally, it appears like a very pointed polygon, in which every side is concave or, alternatively, a shape that looks like a circle with angles added in the spaces between the radial stripes, or a polygonal shape in which every side is convex.
The reciprocal anomalous counterparts of these conditions, obtained by removing the geometrical/polygonal contours, reveal different results. In the first case, one sees a perfect circle; in the second case, a polygon with blunted vertices, or a circular shape with angular protrusions; in the third case, a deformed circle.
These results are inconsistent with some theoretical models proposed to explain the emergence of anomalous contours, namely, all the top-down models expressed in terms of cognitive constructions and perceptual hypotheses, or in terms of global figural organizations. Rather, these comparisons suggest a different interpretation for the two phenomena (the illusion of angularity and anomalous contours). This interpretation is based on dynamic interactions or on network computations that synthesize both real and anomalous contours.
BradleyD RPetryH M, 1977“Organizational determinants of subjective contours: The subjective Necker cube”American Journal of Psychology90253–262
4.
BrignerW LGallagherM B, 1974“Subjective contour: Apparent depth or simultaneous brightness contrast?”Perceptual and Motor Skills381047–1053
5.
BrunoNGerbinoW, 1987“Amodal completion and illusory figures: An informational– processing analysis” in The Perception of Illusory Contours Eds PetrySMeyerG E (New York: Springer) pp 220–222
6.
CorenS, 1972“Subjective contours and apparent depth”Psychological Review79359 – 363
7.
DayR HJoryM K, 1978“Subjective contours, visual acuity, and line contrast” in Visual Psychophysics: Its Physiological Basis Eds ArmingtonJ CKrauskopfJ EWootenB R (New York: Academic Pres) pp 331–340
8.
FarnèM, 1968“Alcune osservazioni con linee virtuali e margini quasi percettivi”Bolletino Società Italiana Biologia Sperimentale441613–1616
GregoryR L, 1987“Illusory contours and occluding surfaces” in The Perception of Illusory Contours Eds PetrySMeyerG E (New York: Springer) pp 81–89
13.
GrossbergS, 1983“The quantized geometry of visual space: The coherent computation of depth, form, and lightness”Behavioral and Brain Science6625–692
14.
GrossbergS, 1984“Outline of a theory of brightness, color, and form perception” in Trends in Mathematical Psychology Eds DegreefEVan BuggenhautJ (Amsterdam: North-Holland)
15.
GrossbergS, 1987“Cortical dynamics of three-dimensional form, color, and brightness perception: I. Monocular theory”Perception & Psychophysics4187–116
16.
GrossbergSMingollaE, 1985a“Neural dynamics of form perception: Boundary completion, illusory figures, and neon color spreading”Psychological Review92173–211
17.
GrossbergSMingollaE, 1985b“Neural dynamics of perceptual grouping: Textures, boundaries, and emergent segmentations”Perception & Psychophysics38141–171
18.
GrossbergSMingollaE, 1987a“The role of illusory contours in visual segmentation” in The Perception of Illusory Contours Eds PetrySMeyerG E (New York: Springer) pp 116–124
19.
GrossbergSMingollaE, 1987b“Neural dynamics of surface perception: Boundary webs, illuminants, and shape from shading”Computer Vision, Graphics, and Image Processing37116–165
20.
von GrunauM W, 1979“The involvement of illusory contours in stroboscopic motion”Perception Psychophysics25205–208
21.
von HelmholtzH L F, 1867Handbuch der physiologischen Optik (Leipzig: Voss)
KanizsaG, 1979Organization in Vision (New York: Praeger)
28.
LawsonR BGulickW L, 1967“Stereopsis and anomalous contour”Vision Research7271–297
29.
MeyerG EFishD, 1987“Illusory contours, texture segregation, and a configural inferiority effect” in The Perception of Illusory Contours Eds PetrySMeyerG E (New York: Springer) pp 224–234
30.
MeyerG EGargesC, 1979“Subjective contours and the Poggendorff illusion”Perception & Psychophysics26302–304
31.
MeyerG EPetryH M, 1987“Top-down and bottom-up: The illusory contour as a microcosm of issues in perception” in The Perception of Illusory Contours Eds PetrySMeyerG E (New York: Springer) pp 3–19
32.
MeyerG EPhillipsD, 1980“Faces, vases, subjective contours and the McCollough effect”Perception9603–606
33.
MinguzziG, 1982“Figure anomale: Le modificazioni di chiarezza indotte dalla fine di linee”reports of the Institute of Psychology, University of Trieste, Trieste, Italy
34.
MinguzziG, 1987“Anomalous figures and the tendency to continuation” in The Perception of Illusory Contours Eds PetrySMeyerG E (New York: Springer) pp 71–74
35.
PastoreN, 1971Selective History of Theories of Visual Perception, 1650–1950 (New York: Oxford University Press)
36.
PinnaB, 1991“Descrizione dinamica ed illusione di angolarità”Rivista di Psicologia (in press)
37.
PomerantzJ RGoldbergD MGolderP STetewskyS, 1981“Subjective contours can facilitate performance in a reaction-time task”Perception & Psychophysics29605–611
38.
PomerantzJ RKubovyM, 1986“Theoretical approach to perceptual organization” in Handbook of Perception and Human PerformancesVolume 2, Eds BoffK RKaufmanLThomasJ P (New York: John Wiley) pp 1–46
39.
PurghèF, 1989“Il ruolo dell'incompletezza figurale e del completamento amodale nella formazione di superfici anomale”Giornale Italiano di Psicologia16101–118
40.
RamachandranV S, 1985“Apparent motion of subjective surfaces” in a special issue on motion perception Ed. RamachandranV S, Perception14127–134
41.
ReynoldsR I, 1981“Perception of an illusory contour as a function of processing time”Perception10107–115
42.
RockI, 1983The Logic of Perception (Cambridge, MA: Bradford Books/The MIT Press)
43.
RockI, 1987“A problem-solving approach to illusory contours” in The Perception of Illusory Contours Eds PetrySMeyerG E (New York: Springer) pp 62–69
44.
SigmanERockI, 1974“Stroboscopic movement based on perceptual intelligence”Perception39–28
45.
SmithA TOverR, 1975“Tilt aftereffects with subjective contours”Nature (London)257581–582
46.
SmithA TOverR, 1976“Color-selective tilt aftereffects with subjective contours”Perception & Psychophysics20305–308
47.
SmithA TOverR, 1977“Orientation masking and tilt illusion with subjective contours”Perception6441–447
48.
SmithA TOverR, 1979“Motion aftereffect with subjective contours”Perception & Psychophysics2595–98
49.
WeisstenNMatthewsMBerbaumK, 1974“Illusory contours can mask real contours”Bulletin of the Psychonomic Society4266 (Abstract)
