Abstract
An array of black discs surrounded by a set of coloured annuli forming a ramp, whose luminance increases outward, is perceived scintillating of complementary colours when moving the gaze from an element to another. We call this illusion Coloured Flashing Spots (CFS).
It differs from simple colour contrast in being vivid, self luminous and lustrous, in not being a property of the inducing surface and occurring in peripheral rather than in foveal vision.
It is phenomenally related to the Flashing Anomalous Colour Contrast (FACC) (Pinna, Spillmann, Werner 2004) from which differs in not depending on the radial lines for its flashing and in that the chromatic annuli form a ramp profile instead of a square decrement. Additionally, while the FACC is stronger when the inner disc has the same luminance as the surrounding annulus, here the flashing drops if the disc has a minimal brightness contrast compared to the mean annulus brightness, becoming a simple simultaneous colour contrast. Conversely, replacing the grey disc in the FACC with a white or black one, we obtain an enhanced white or black respectively.
The CFS can be partially explained by mechanisms subtending simultaneous colour contrast and brightness-darkness induction as in the Hermann Grid illusion. Further mechanisms accounting for the role of the ramp profile are needed to explain how the reversing of the annulus ramp luminance and the use of a white disc in place of a black one, induces a flashing exhibiting very similar vividness, saturation and lightness to the previous condition.
this work was supported by Alexander von Humboldt Foundation, Fondazione Banco di Sardegna, ERSU