RP is a case of "developmental" prosopagnosia who, according to brain-imagi
ng segmentation data, shows a reduction in volume of a limited set of struc
tures of the right hemisphere. RP is as accurate as control subjects in tas
ks requiring the perception of nonface objects (e.g., matching subordinate
labels to exemplars, naming two-tone images), with the exception of one per
ceptual task: The matching of different perspectives of amoebae-like stimul
i (i.e.. volumes made of a single smooth surface). In terms of speed ("effi
ciency") of responses, RP's performance falls clearly outside the not nial
limits also in other tasks that include "natural" but nonface stimuli (i.e.
, animals, artifacts). Specifically, RP is slow in perceptual judgements ma
de at very low (subordinate) levels of semantic categorization and for obje
cts and artifacts whose geometry present much curved features and surface i
nformation. We conclude from these analyses that prosopagnosia can be the r
esult of a deficit in the representation of basic geometric volumes made of
curved surface. In turn, this points to the importance (necessity) for the
normal visual system of such curved and volumetric information in the iden
tification of human faces.