Robert writes -

There is however something to be said however for keeping things simple. If you can teach something, without artificially adding to the list of requirements, then you are likely to save yourself some headaches.

Sure there is something to be said for this. But I think you might agree there is not a scientific measure to be made here, outside (perhaps) of contexts that are so narrow as to be meaningless for any practical application. What is more scientific, it seems to me, are identifiable phenomena like the law of diminishing returns, and the "law" of unintended consequences of activity within the realm of real world complexity which is beyond our ability to comprehend. At some point, within a particular context and where an educational process is the goal, easier becomes too easy. We seem to agree there. Based on feel. The legal term for studies (at least the ones I have heard discussed here) that on the surface purport to deal with these issues is "loophole". Since they are not in essence in any sense scientific, there is no coherent scientific argument to be made to refute them. They rely upon their institutional affiliate and their ability to get funded as their authority. And will stand with more authority than they merit. That is a real *social* phenomena. I believe more real and measurable then the study itself. Which leaves the alternative, at least for those of us unaffiliated, to rant at them. Or at least that is the only alternative I have been able to see. But nobody likes a ranter. I should know ;) Art