I've taught Cartagena to a variety of people, from my 5 year old nephew to hard core gamers. It's interesting to see how they play. Colovini's games only tell you what you can do, not what you're supposed to do to win, and people are really left to figure out their own strategy. Cartagena is a simple enough game that you can see the strategy develop in as little as one game, so it's a rare opportunity to study how people learn to play a game.
Let's start with the gamers from Critical Mass. I explained the rules, and, knowing that gamers would want to be competitive, I explained "it's a race between the last guys on your team, not the first guys". It seems to me that once you get that idea embedded in your strategy, the remaining points are very subtle. However, not all of the players could cope with that straight away. Some made an opportunistic rush for the boat, but then fell behind due to the neglect of their other pirates. On the other hand, some players understood straight away, and I got beaten.
Stepping down a level, consider my kid (who's 9). When I taught him the game, I didn't know how to play either (he's a very good person to learn games with, as he'll play almost anything once, and if I'm not careful he'll beat me), so I wasn't ableto give him any strategy hints. He went for the "get guys into the boat fast" strategy. A couple of games later, I mentioned to him what I'd figured out about the last guys, and he started changing his strategy. I reckon it took about 2 games for him to stop doing the wrong thing, and start playing moderately competitively.
Now consider my 5yo nephew. He likes this game because it has pirates and daggers and guns. He likes to get his guy on the boat first, at any cost. I played against him this morning, and the only thing I could say that would prevent him from moving the front guy was "look, if you get him in the boat you'll just need to move him off again so you can get more cards". That made sense to him, so he did something else to get more cards, then he moved the front guy onto the boat. All through the game I was suggesting moves to him, and he accepted just enough of my suggestions so that he had enough cards to keep moving his front guy and then survive to get more cards. I think he has played 4 games now, and although he completely understands the mechanics, strategy is beyond him. He appreciates playing the game, anyway.
So, let's consider what we've learnt here. For a gamer, it takes one or two games to learn how to play. For a 9yo, maybe 4 games. For a 5yo, the value approaches infinity. It seems that somewhere between 5 and 8 (based on other experiments on my kid) something develops in the gamer mind to enable the formation of strategies. Maybe some 5yos have it, but my nephew only started playing games last year. When I first suggested that he could play Nobody But Us Chickens by himself, my sister told me "you've got no chance", and then we were all amazed. There's definitely a skill there, that either needs to be learned or developed, I'm not sure. Can you learn how to develop strategies by watching other people do it? My kid has so far been not very good at developing complex strategies, e.g. in San Juan, but then he mostly avoids that sort of complexity. Is it the same skill taken to another level? Or is a strategy derived from combination of interacting parts (as in San Juan, or a CCG) different from a strategy which can be expressed as a couple of rules to be followed? Hmm... must devise some more experiments to use upon the children.