Is the N170 face specific? Controversy, context, and theory
Earp B., Everett JAC.
In cognitive science, there is an ongoing debate about the architecture of the mind: does it consist of a number of mental “organs” each managing a different function in isolation, or is it more of general processor, adaptable to a wide range of tasks? One corner of this debate has centered on face processing. This is because face-perception is crucial to normal human functioning and some evidence shows that faces may be processed by the brain in a privileged way compared to other types of stimuli. For example, in EEG brain recordings, the N170 is a characteristic signal that occurs after a participant is exposed to an image of a face, but it is much less pronounced when other stimuli are shown. More than 15 years of research on the “N170 face effect” have yielded the standard view that the N170 is at the very least face-sensitive, and possibly even face-specific, that is, indexing modular processes tied exclusively to facial geometries. The specificity claim is clearly stronger, and hence subject to significant controversy; while the more conservative “sensitivity” claim had been regarded (until recently) as effectively settled. Nevertheless, Thierry and colleagues, in a contentious 2007 article, sought to undermine even this ‘conservative’ consensus: they argued that the apparent face-responsiveness of the N170 in prior research was due to systematic flaws in experimental design. Fiery debate has followed. In this review, we put the debate in its historical and philosophical context, and try to spell out some of the theoretical and logical assumptions that underlie the claims of the competing camps. We then show that the best available evidence counts, at least partially, against the Thierry et al. construal of the N170. Accordingly, it would be premature to abandon the “conservative” account of the N170, according to which it is— minimally—responsive to faces. We conclude by returning to the more controversial claim about face-specificity, and try to clarify what such a view would entail from a theoretical standpoint.