The field of cognitive psychology has had a great deal of success in understanding the mind as an abstract information processing system, without regard to its actual instantiation in the human nervous system. One benefit of this approach is that principles articulated in terms of information can then be implemented on any sort of hardware, and this surely has facilitated the rapid development of artificial intelligence systems. However, as psychologists, our primary interest is in human cognition which is mediated by a specific piece of hardware, the brain. Because our brain is the result of evolutionary pressures that select for biological fitness and reproductive success we can expect that the human mind will have some design features that may not be predictable from an information engineering standpoint. Thus, the most elegant model of some cognitive process, even if it predicts a range of behavioral data, may not be the right model unless it is also neurologically plausible.