It is obvious that some things in nature are conscious, for example, human beings. It is equally obvious that some things in nature are not, for example, blades of grass. What is not obvious is where to draw the line. Some philosophers and scientists think that a fruitful way to proceed on the question of animal consciousness is via an investigation of their metacognition. If animals behave in ways that indicate that they have a cognitive grasp on how things appear to them, and not just on how they are, then the obvious conclusion is that things really do appear to them in various ways. Fish exhibit trade-off behavior. In one experiment, trout were trained to feed in a part of the aquarium where they subsequently got a shock to the flank. It was found that the number of feeding attempts decreased with increased shock intensity.