B. Laeng et al., Identifying objects in conventional and contorted poses: contributions of hemisphere-specific mechanisms, COGNITION, 70(1), 1999, pp. 53-85
Three experiments were designed to rest the hypothesis that different mecha
nisms are used to encode objects seen in unfamiliar contortions than are us
ed to encode objects seen in conventional poses. When a familiar non-rigid
form (e.g. an animal) is seen in a contorted pose, we hypothesize that obje
ct identification may be achieved by (1) encoding the object's parts separa
tely, (2) encoding the spatial relations among the parts, and (3) matching
these encodings to a stored structural description. However, once this form
has become familiar, its global shape can be directly matched to informati
on stored in memory. Based on the idea that 'categorical' spatial relations
are encoded better by the left cerebral hemisphere and are used in structu
ral descriptions, we predicted a left-hemisphere advantage when one first e
ncodes contorted poses; in contrast, based on the idea that overall shapes
are encoded better by the right hemisphere, we predicted a right-hemisphere
advantage for encoding the same shapes after they are familiar. Three expe
riments confirmed these predictions, which supports the hypotheses that dif
ferent visual mechanisms operate in the recognition of familiar and unfamil
iar views of known non-rigid objects. Moreover, correlational analyses betw
een visual-field differences in several perceptual tasks (matching whole pi
ctures to names, body parts to the whole body, and judging categorical spat
ial relations) revealed that the degree and lateralization of categorical s
patial encoding predicts the left hemisphere's initial advantage in the ide
ntification of contorted shapes. (C) 1999 Elsevier Science B.V. All rights
reserved.