 In comparative psychology, and especially when following Morgan’s Canon, simpler explanations are taken by default as the null hypothesis. This means that they are assumed to be true unless proven otherwise, and that the burden of proof falls on the side of more complex explanations. For example, research into causal reasoning in animals takes as its null hypothesis animals’ ability to learn associations between different events. The experiments then probe into whether animals are not just capable of this simple form of learning, but whether they have the more complex capacity to comprehend that some events cause others. When the experimental data support both a simple hypothesis and a more complex one, it is standard among scientists to prefer the simpler explanation. For instance, some have argued that the experiments done to test whether animals are capable of metacognition (or thinking about their thoughts) can in fact be passed by reasoning solely in first-order terms (or thinking about the world). Since first-order thinking is assumed to be a simpler explanation of the data, it has been argued that this explanation ought to be favored (e.g., Carruthers 2003; Hampton 2009).