1/f2 Characteristics and Isotropy in the Fourier Power Spectra of Visual Art, Cartoons, Comics, Mangas, and Different Categories of Photographs

Art images and natural scenes have in common that their radially averaged (1D) Fourier spectral power falls according to a power-law with increasing spatial frequency (1/f2 characteristics), which implies that the power spectra have scale-invariant properties. In the present study, we show that other categories of man-made images, cartoons and graphic novels (comics and mangas), have similar properties. Further on, we extend our investigations to 2D power spectra. In order to determine whether the Fourier power spectra of man-made images differed from those of other categories of images (photographs of natural scenes, objects, faces and plants and scientific illustrations), we analyzed their 2D power spectra by principal component analysis. Results indicated that the first fifteen principal components allowed a partial separation of the different image categories. The differences between the image categories were studied in more detail by analyzing whether the mean power and the slope of the power gradients from low to high spatial frequencies varied across orientations in the power spectra. Mean power was generally higher in cardinal orientations both in real-world photographs and artworks, with no systematic difference between the two types of images. However, the slope of the power gradients showed a lower degree of mean variability across spectral orientations (i.e., more isotropy) in art images, cartoons and graphic novels than in photographs of comparable subject matters. Taken together, these results indicate that art images, cartoons and graphic novels possess relatively uniform 1/f2 characteristics across all orientations. In conclusion, the man-made stimuli studied, which were presumably produced to evoke pleasant and/or enjoyable visual perception in human observers, form a subset of all images and share statistical properties in their Fourier power spectra. Whether these properties are necessary or sufficient to induce aesthetic perception remains to be investigated

Alkan’s for organ

Stylistic and pitch-related data derived from the score of Alkan’s Petits Préludes for organ are analyzed using nonparametric correlations and multidimensional scaling, and the results used to reconstruct his compositional process. The reconstruction is then verified by comparing it to an existing cognitive model of musical composition and Alkan’s use of multiple compositional constraints discussed as an example of a strategy employed by master composers to reduce their problem space. The tidy fit of the reconstruction to the model and the agreement of the evidence with a number of previous findings and hypotheses concerning the cognitive processes underlying musical composition strongly suggests that the model and similar analyses of musical variables could be applied to works by other composers and used as a basis for or an adjunct to musicological and psychological studies of the compositional process, particularly when limited to a post hoc analysis or by a finite dataset

The effect of tone duration on auditory stream formation

cote interne IRCAM: Beauvois98a/National audienceIn a study in which the effect of tone duration on the formation of auditory streams was investigated, subjects were presented with 15-sec alternating pure-tone sequences(ABAB...) and were asked to orient their attention over theduration of the sequence toward hearing either a temporallycoherent or a segregated percept. At stimulus offset, thesubjects indicated whether their percept at the end of thestimulus had been that of a temporally coherent ABAB trillor that of segregated A and B streams. The experimentalresults indicated that the occurrence of stream segregationincreases as (1) the duration of the A and B tones increasesin unison and (2) the difference in duration between the A and B tones increases, with the duration difference betweenthe tones producing the strongest segregation effects. Acomparison of these experimental results with those of otherstudies strongly suggests that the time interval betweenthe offset and onset of consecutive tones in the same frequencyrange is the most important temporal factor affecting auditorystream formation. Furthermore, a simulation of the experimentalresults by the Beauvois and Meddis (1996) stream segregationmodel suggests that both the tone duration effects reportedhere and Gestalt auditory grouping on the basis of temporalproximity can be understood in terms of low-levelneurophysiological processes and peripheral-channeling factors