Modular and hierarchical brain organization to understand assimilation, accommodation and their relation to autism in reaching tasks: a developmental robotics hypothesis

By assimilation children embody sensorimotor experiences into already built mental structures. Conversely, by accommodation these structures are changed according to the child's new experience. Despite the intuitive power of these concepts to trace the course of sensorimotor development, they have gradually lost ground in psychology. This likely due to the lack of brain-related views capturing the dynamic mechanisms underlying them. Here we propose that brain modular and hierarchical organization is crucial to understanding assimilation/accommodation. We devise an experiment where a bio-inspired modular and hierarchical mixture-of-experts model guides a simulated robot to learn different reaching tasks by trial-and-error. The model gives a novel interpretation of assimilation/accommodation based on the functional organization of the experts allocated through learning. Assimilation occurs when the model adapts a copy of the expert trained for solving a task, to face another task requiring similar sensorimotor mappings. Experts storing similar sensorimotor mappings belong to the same functional module. Accommodation occurs when the model uses non-trained experts to face tasks requiring different sensorimotor mappings (generating a new functional group of experts). The model also provides a new theoretical framework to investigate assimilation/accommodation impairment, and proposes that such impairment might be related to autism spectrum disorder.