How vision and self-motion combine or compete during path reproduction changes with age

Human adults can optimally integrate visual and non-visual self-motion cues when navigating, while children up to 8 years old cannot. Whether older children can is unknown, limiting our understanding of how our internal multisensory representation of space develops. Eighteen adults and fifteen 10- to 11-year-old children were guided along a two-legged path in darkness (self-motion only), in a virtual room (visual + self-motion), or were shown a pre-recorded walk in the virtual room while standing still (visual only). Participants then reproduced the path in darkness. We obtained a measure of the dispersion of the end-points (variable error) and of their distances from the correct end point (constant error). Only children reduced their variable error when recalling the path in the visual + self-motion condition, indicating combination of these cues. Adults showed a constant error for the combined condition intermediate to those for single cues, indicative of cue competition, which may explain the lack of near-optimal integration in this group. This suggests that later in childhood humans can gain from optimally integrating spatial cues even when in the same situation these are kept separate in adulthood.