Sequential organization is key to human and animal behaviour. Rejected idea that sequential organization is the result of associative chaining. Movement can occur even when sensory feedback is interrupted. Some movement sequences are too quick for elements to be triggered by preceding elements. Ex: children who make vocabulary mistakes to children to have a high level of grammar. Critical periods: child must learn certain things before certain ages. These plans obviously draw upon information about the body and about the environment. Cogs sc. grew out these basic ideas (distal, rather than proximal) Developing these ideas was made much easier by two mathematical theories. Organisms pick up and process info about the environment. Break complex serial ordered behaviour down into subtask. (reflections of descartes, quid voir) The second, to divide each of the difficulties under examination into as many parts as possible, and as might be necessary for its adequate solution.