Spatial performance and perceptual asymmetries in beginning readers: shift of hand advantage in dichhaptic tasks

The stability of perceptual asymmetries was studied in two groups of 6-year-old, right-handed children (normal, NL, and poor, PL) learning reading, by means of two experiments occurring at a year's interval (Experiment I and Experiment II). A dichhaptic procedure derived from S. F. Witelson's method (1974, Cortex, 10, 3-17) was used. With group data, perceptual asymmetries were stable over time, whereas with individual data, perceptual asymmetries were highly variable. NL children demonstrated a left-hand advantage at the group level in both Experiment I and Experiment II, with relatively little individual evolution over time. No significant hand advantage was found in PL children in Experiment I, but dramatic alterations occurred in Experiment II where all PL children shifted to a left-hand advantage. This shift was accompanied by an improvement in spatial performance. Such changes in perceptual asymmetry might be of an adaptive nature. Individual changes across time may be related to developmental plasticity (cerebral maturation) and/or neurocognitive flexibility (differential activation of cerebral subsystems).