Abstract
Hemispheric asymmetries in the perception of hierarchically arranged visual stimuli (i.e., “hierarchical perception”) have long been established, and a myriad of studies have demonstrated that the left hemisphere (LH) is biased towards local processing and that the right hemisphere (RH) is biased towards global processing. However, the mechanisms that produce these asymmetric biases are still debated. Hubner and Volberg (2005) recently proposed that the identities of shapes in hierarchical displays are initially represented separately from their hierarchical level (local/global), and that the LH is more involved in binding shapes to the local level while the RH is more involved in binding shapes to the global level (“integration theory”). This is in contrast to previous models implicating the importance of attentional selection of spatial scale in hierarchical perception (e.g., Double Filtering by Frequency (DFF) theory, Ivry & Robertson, 1998), which proposes that asymmetric biases towards relatively high (by the LH) and relatively low (by the RH) SFs underlie the hemispheric asymmetry in local versus global processing, respectively. Rather than considering these two theories as mutually exclusive, we unify them into a single framework and provide evidence that selective attention of SF is the medium for hierarchical integration. Attention to the higher or lower SFs in a previously presented compound grating modulated shape-level binding errors in a subsequently presented hierarchical display. Specifically, attentional selection of higher SFs facilitated binding by the LH of shapes to the local level and attentional selection of lower SFs facilitated binding by the RH of shapes to the global level.