Building Spatial Skills: Development of Spatial abilities across the sensory systems in children with and without visual impairment

Spatial perception is a fundamental ability that enables humans to orient, navigate, and interact effectively with their environment. The main objective of my Ph.D. project was to investigate how spatial representations develop during early life, and how sensory experience shapes the unisensory and multisensory mechanisms supporting spatial perception. In particular, my Ph.D. aimed at: i) characterising the development of auditory spatial localisation abilities during early childhood; ii) examining how children integrate multisensory spatial information, focusing on audiovisual cues and spatial disparity between objects; iii) investigating the development and neural mechanisms of audio-tactile multisensory integration in early childhood, in both typically developing children and children with severe visual impairment. To achieve these aims, I conducted a series of behavioural and neurophysiological studies across different developmental stages, using age-appropriate experimental paradigms. First, behavioural experiments in preschool children were used to assess the development of auditory spatial localisation. Second, audiovisual spatial object segregation was investigated behaviourally in toddlers using dynamic stimuli, and multisensory performance was evaluated against predictions from computational models of cue combination, including Maximum Likelihood Estimation, to assess whether integration approached optimality. Finally, high-density electroencephalography (EEG) was employed in infants and toddlers to investigate the neural correlates of early audio–tactile multisensory processing, allowing behavioural responses to be directly linked to cortical activity. i) Results on auditory spatial localisation indicated comparable performance between preschool children and adults along the azimuth plane, with residual differences emerging primarily for elevation cues. ii) At the multisensory level, results from the audiovisual segregation study showed that preschool children tended to perceive the spatial discrepancy of objects if the stimulation is bimodal. Substantial inter-individual variability emerged, reflecting differences in sensory weighting strategies during development. iii) The investigation of audio–tactile integration in early childhood demonstrated that multisensory gain is present early in development in both sighted and severely visually impaired children. However, clear differences emerged in neural organisation: while sighted infants recruited integrative cortical networks and maintained multisensory processing under spatial conflict, visually impaired infants relied more strongly on tactile, body-centred representations, showing reduced engagement of integrative mechanisms when sensory cues were incongruent. Overall, the findings of this Ph.D. project contribute to a comprehensive understanding of how spatial perception develops from infancy to early childhood. They demonstrate that multisensory mechanisms emerge early but are progressively shaped by sensory experience and task demands, with visual input playing a critical role in calibrating spatial representations and supporting flexible multisensory organisation. By integrating behavioural and neural evidence from both typical and atypical developmental trajectories, this work advances our understanding of the mechanisms through which children construct spatial knowledge in a multisensory world.