This section starts with a discussion on the limitations of the `symbol systems' perspective to perception. The symbolic approach, pursued traditionally by artificial intelligence, assumes a one-way processing of visual information from raw sensory data to symbolic representations. The sensorimotor approach, in contrast, assumes that visual perception depends on a motor representation. This section reviews experimental evidence of an (involuntary and subconscious) influence of action on the visual perception, and closes with a collection of hypothesis on perception based on sensorimotor models.