ABSTRACT
Hitting a ball onto a target by pushing it with a stick used like a bat may seem easy, but for young children the problems begin when the target is not situated more or less straight in front of them. Pushing a cylinder (or a similar device made up of two wheels of the same size, one at each end of an axle) makes the task even more difficult, while further complica tions are added when the object to be pushed is asymmetrical, such as a tmncated cone (a tumbler) or a device with two dif ferent-sized wheels fixed to an axle (isomorphic to the two plane surfaces of the truncated cone). Because in this last situ ation the object's trajectory forms a curve, there arises the problem of the interpretation of the respective roles of the child's own actions when he gives the object a push with the stick, and of the objective, geometric properties of the ob ject itself. This situation therefore provides an opportunity
to study a particular case of the cognizance of an action and of seeing how the child relates his observations on the object to what he notices of his own action.
