We have just published a paper in Animal Cognition on cognitive strategies in orangutans solving a 'puzzle-tube' task. The task that the orangutans faced was to try to remove a walnut from the tube. To do so, they had to guide the walnut from its central position towards one end of the tube, past obstacles. The tube was set up in such a way that each of the 64 trials presented a unique configuration of obstacles: for example, the walnut might roll over a gap in the floor of the tube or it might fall through it, where it might roll down another tube towards the orangutan, or away from it and out of its reach.
We were particularly interested in how orangutans solved the task, and simulated possible outcomes for various procedural rules and combinations of rules in order to try to understand these processes. We found that two out of three orangutans were able to solve the task, suggesting that they were able to take into account some of the obstacles in advance of acting in order to retrieve the reward.