Facial Emotion Processing in the Laboratory (and elsewhere): Tradeoffs between Stimulus Control and Ecological Validity

1] demonstrates that simple schematic faces evoke neural responses comparable to those evoked by photographic face stimuli. The authors argue that this shows that schematic visual stimuli may still validly represent face processing, although it has been argued that such non-photographic faces lack many of the visual properties of the human face. In this commentary I would like to elaborate on this issue. Indeed similar claims of lack of ecological validity have been made to photographic face stimuli as well. It is true that viewing faces and facial expressions of emotion in natural contexts is quite different from the viewing conditions usually present in face perception experiments in the laboratory. But this is not a problem that is specific to face processing studies and stimuli. Indeed any laboratory study is faced with issues of ecological validity. Ultimately it is a matter of the tradeoff between ecological validity and control of experimental conditions and extraneous variables. For face processing in particular, many different kinds of stimuli have been used in the literature, with varying degrees of proximity to natural viewing conditions. Simplified stimuli like schematic faces, as those used by Maratos et al [1] have featured in some studies on face processing (e.g., [2]). Photographic faces, on the other hand, retain most of the actual visual features of faces and have