We investigated whether the perception or production of a given line
length in normal subjects varies according to where in peripersonal
space the line is perceived or produced. We also investigated the
influence of the direction of movement used to make the line. In
Experiment 1, blindfolded normal subjects were asked to estimate
distances while the examiner moved the subject's hand in proximal
(medial) or distal (lateral) space, moving centripetally or
centrifugally. The subjects showed a spatial effect, perceiving the
same length as shorter in proximal space than distal space. This result
could be related to either a proximal spatial attentional bias or an
anisometric representation of spatial distances. In Experiment 2, we
attempted to dissociate these hypotheses by studying blindfolded normal
subjects, who were requested to produce horizontal lines of a given
length (100 or 200 mm) in proximal versus distal peripersonal
space using centripetal or centrifugal movements. Centrifugal movements
in proximal space were the longest; centrifugal movements in distal
space were the shortest; in between were the proximal centripetal and
distal centripetal movements which did not differ from each other.
These results suggest that in peripersonal space the perception of
length in normal subjects is most consistent with anisometric mental
representation where the size of mental representations of length units
decreases as a function of the distance from the subject's
midsagittal plane. Length production, however, may depend on an
interaction of the anisometric mental representation and the
premotor/intentional factors. (JINS, 2004, 10,
913–919.)