The paper by Meares and colleagues1 in this issue of J Neurol Neurosurg Psychiatry concerns the implications of defining a syndrome by symptoms that have a high base rate of occurrence in the general population or in other syndromes (see page 300). The issue of neglect of base rates was raised five decades ago in the seminal work of Paul Meehl,2 who pointed out that “the chief reason for our ignorance of the base rates is nothing more subtle than our failure to compute them” (page 234). There are now systematic collections of base rate data in the general population3 and in groups relevant to neuropsychology, …