Abstract
Many natural phenomena exhibit properties that follow a 1/f fractal-like distribution. In vision, this is most readily observed in the amplitude spectra and edge geometry of natural scenes and visual art. As a result, fractal geometries have been widely considered in the explanation of universal aesthetic experience and beauty. We investigated the aesthetic perception of 1/f statistics at their most fundamental physical manifestations across three sensory domains: vision, touch and audition. In our first experiment (n = 51), we compared the preferences for visual and tactile stimuli varying in discrete increments of amplitude spectrum slope (α). For visual stimuli, α was independently manipulated across both the spatial structure of a 1/f image, and the temporal structure of a 1/f image sequence varying across time. Tactile stimuli were created by extruding 1/f images into 3D models then printed into blocks of physical textures. Preference was measured using a two-alternative forced choice procedure. We found visual preference for spatially varying 1/f images peaked for intermediate slopes - equivalent to those typically found in natural scenes. For temporally varying 1/f images and tactile textures the steepest slopes were the most preferred. Perceptually, these equated to the slowest moving images and the smoothest surface textures. In a subsequent study, musical melodies were created with α-adjusted 1/f pitch sequences and presented to participants in a 2AFC preference task (n = 72). We found sequences with the most predictable and regular melodies were the most preferred. Our results support the appeal of natural fractal statistics in still visual images. Interestingly, this preference appears to shift towards steeper values of α for stimuli presenting a temporal component, such as those found in moving images, the exploration of surfaces and the progression of musical melodies. Individual differences and internal consistency in preference across modalities will be discussed.