In this chapter we discuss the relationships between motor and cognitive skills in a developmental perspective, usually considered as two separate categories of behavior. We have try to demonstrate that the processes and mechanisms underlying motor and cognitive skills have similarities. For the purpose of this chapter, we have considered cognitive and motor skills separately. Particular attention will be paid to "seriation skills", from both a motor point of view and a cognitive one. A large number of studies have been done from the cognitive point of view in order to discover how children succeed in seriating objects or events according to a given property (size, weight, etc...). We have studied, from a motor point of view, how children manage to adjust certain parameters of their actions (velocity, amplitude, force, etc) in relation to the variations of different properties of the objects. The major problem is to know whether plans (cognitive labels) and programs (motor labels) have the same underlying mechanisms or whether, on the contrary, they have different kinds of processing systems.