Abstract

Comparative psychology experiments typically test a null statistical hypothesis against an alternative. Coupled with Morgan’s canon, this is often taken to imply that the model positing the simpler psychological capacity should be treated as a ‘default’ that must be ruled out before any other model can be accepted. It has been posited that this practice neglects evidence. I argue that the problem is deeper, including the way it structures the evaluation of evidence that is considered; it frames model choice around the acceptance or rejection of a default. I oppose this default framing in all its forms and develop an evidentialist alternative. Default framing fails to respect the difference between experimental statistical hypotheses and substantive hypotheses such as models. It is not actually supported by the use of null hypothesis significance testing (which I retain), it distorts the weighting of evidence, and it systematically biases practice.