The accentuation principle of figure–ground segregation and the downbeat illusion

Pinna and Sirigu (2011) demonstrated a new principle of grouping, called the accentuation principle, stating that, all else being equal, elements tend to group in the same oriented direction of the discontinuous element placed within a whole set of continuous/homogeneous components. The discontinuous element behaves like an accent, i.e. a visual emphasis within the wholeness of components as shown in the next section. In this work, the accentuation principle has been extended to new visual domains. In particular, it is shown how this principle affects shape perception. Moreover several visual object attributes are also highlighted, among which orientation, spatial position, inner dynamics and apparent motion that determine the so-called organic segmentation and furthermore tend to induce figure–ground segregation. On the basis of the results of experi- mental phenomenology, the accentuation can be considered as a complex principle ruling grouping, figure– ground segregation, shape and meaning formation. Through a new musical illusion of downbeat, it is also demonstrated that this principle influences perceptual or- ganization not only in space but also in time and, thus, in both visual and musical domains. This illusion can be heard in eight measures of Pagodes, a solo piano music by Claude Debussy (1862–1918), where a strong physi- cal–perceptual discrepancy in terms of upbeats and downbeats inversion is strongly perceived in both staves.