It appears some pilots instinctively do the exact opposite! They start to climb. Why is that?
This is a fascinating psychological topic. The general consensus in the literature is that pilots revert to a primitive concept that equates flying with climbing. This makes sense in that in order to fly one must climb up from the ground. What do you do when you want to fly? You go up. Mentally, the pilot goes back to square one and tries to take off all over again. In the AF447 case it was revealed that all the way into the sea the pilots kept trying to get the plane to /climb/ and even verbalized that intent. When in fact is they have just flown the plane they would have been OK.
What still remains to be understood is why some pilots revert to an incorrect cognitive map under stress. Is it that they were poorly trained to begin with? Or perhaps they have some basic psychological predisposition?