Study showing how different ages of children learn about balancing objects I'm trying to track down a source for an idea I saw in a documentary a while ago (sorry, no idea where!) It demonstrated how children learn differently at different ages, through showing them balancing an unevenly weighted bar (in other words, a bar that looks the same along its length, but is in fact heavier at one end).

Loosely, the programme suggested that: young children (toddlers?) can get such a bar to balance intuitively, through "trial-and-error"; slightly older children (5?) try to balance the bar half way, and so say "it won't balance"; older children again, understand that the bar is not evenly weighted and so once again realise that experimentation is needed to find the balancing point.

Am I completely imagining that I saw some research of this kind? Or does anybody know where I can find a link to such a piece of research?
I suspect you are thinking of Karmiloff-Smith's work. Here's an excerpt from an '88 article almost exactly matching the description. 


  
    Children were asked to balance a series of blocks on a narrow metal support. Some of the blocks had their weight evenly distributed and balanced at their geometric centre. Others had been drilled with lead in one end and, although they looked identical to the first type, they actually balanced way off centre.
    
    [...]
    
    Very briefly, it was shown that 4 and 5 year olds could do this task very easily. They simply picked up each block, moved it along the support until they felt the direction of imbalance, and corrected that by using proprioceptive feedback until the block balanced. By contrast, 6 to 7 year olds placed every block at its geometric centre and were thus incapable of balancing anything but the blocks where the weight was evenly distributed. Finally, 8 to 9 year olds were able to balance all the types of block, as had the youngest subjects.
  


I'm not super familiar with the author, but given the publication time and terminology, this seems like a theoretical predecessor to the more recent work on embodied cognition, dynamic systems and ecological psychology.


  Karmiloff‐Smith, A. (1988). The Child is a Theoretician, Not an Inductivist*. Mind &amp; Language, 3(3), 183-196.