In Genetic Epistemology (*3), Piaget says

"Language appears somewhere about the middle of the second year, but before this, about the end of the first year or the beginning of the second year, there is a sensory-motor intelligence having its own logic - a logic of action. The actions that form sensori-motor intelligence are capable of being repeated and of being generalised. ... Whatever is repeatable and generalisable in an action is what I have called a scheme, and I maintain that there is a logic of schemes. Any given scheme in itself does not have a logical component, but schemes can be coordinated with one another, thus implying the general coordination of actions. These coordinations form a logic of actions that are the point of departure for the logical mathematical structures. ... At the later stage this relationship of class inclusion gives rise to concepts. At the sensori-motor stage a scheme is a sort of practical concept".

and then:

"Between the age of about 18 months and the age of 7 or 8 years when the operations appear [operations = actions which have group-logic - AB], the practical logic of sensori-motor intelligence goes through a period of being internalised, of taking shape in thought at the level of representation, rather than taking place only in the actual carrying out of actions. .. language is certainly not the exclusive means of representation .. [it] is the ability to represent something by a sign or a symbol or another object".