Hand in the Gourd
What makes this so interesting to me is (as always) why it works. I am almost certain it goes like this .... the monkey is looking for a one-step solution to a two-part problem.
To remove his hand, he needs to complete step one: let go of the banana before moving on to step two: pulling his hand out. His brain seeks a one-step solution - which doesn't exist - and so he can't make his escape.
The exact same principle exists within the landscape of Brazilian Jiu Jitsu.
Escaping a tight 'side control' for example, almost certainly requires a multi-step solution - but our first (natural) instinct is to seek a one-step solution. Almost always, a one-step solution does not exist - and we remain stuck the side control.
Once we get our heads around the fact that the answer lies in the multi-step approach - things start to look a little better.
Another way I like to explain this idea is by asking students if they think they can pick up a woollen sweater and rip it in half - pretty difficult. But by finding the right thread, it may be very possible to start pulling and eventually unravel the whole thing. This idea is key to developing effective escapes. We should begin, not by trying to blast out in one big move - but by looking for the right thread that will begin to unravel the opponents position.
if we are 'deep in it' - then it will almost always take us a series of steps to dig ourselves out. if we are only a little way in trouble, then the process of getting out may indeed be a single-step process.
Deep in - start digging - small steps - find the thread.
Hope this helps,