The perception of natural contour
Gilden, D. L., Schmuckler, M. A., & Clayton, K.

We inquire into the way that complex random structure is perceived. The observation that natural curves and surfaces are often fractal suggests that people may be sensitive to their statistical properties. We investigate in three studies the perceptual protocols that underlie discrimination between fractals, and between other types of random contour and fractals. Algorithms for discrimination are constructed that have precisely the same sensitivities as human observers. These algorithms are blind to the integrated scale hierarchy intrinsic to fractal form and operate by imposing a metatheory of structure that is based on a signal/noise distinction. The success of the algorithms implies that self-affinity in random fractals is not perceptually recovered, and that people have a natural disposition to view contour in terms of signal and noise. We propose that this disposition be understood as a principle of perceptual organization.