Mediated facial expressions do not elicit emotions as strongly as real-life facial expressions. In particular, 2D photographs of facial expressions fail to evoke emotions as strongly as live faces, possibly due to the low fidelity of the pictorial presentation. However, we found that 3D facial expressions evoke stronger emotions than their 2D counterparts. Due to the illusion of non-mediation, natural depth levels create the strongest emotional amplifications. In this experiment, we manipulated depth magnitude by varying the distance between the two cameras providing the left and right images for the 3D presentation.

Facial expressions are commonly studied with 2D photographs, while the results are generalized to the real world. Yet stereoscopic images replicate reality more faithfully and thus are more valid stimuli. One could say that 3D photographs trick the brain into thinking that the face in a 3D photograph is more real than in the 2D photograph

Whereas the negative valence and arousal elicited by angry expressions was most significantly amplified at the most natural depth magnitude, the positive valence elicited by happy expressions was amplified in both narrowed and natural depth conditions. The findings are relevant for virtual and augmented reality 3D displays such as Oculus Rift, indicating that 3D content must preferably provide a natural depth percept to provide emotion-evoking experiences.

Currently, 3D is mostly used in action films to emphasize the effects, but it could be also employed to enhance the emotions conveyed by the actors. The article was published in the open-access journal i-Perception: http://ipe.sagepub.com/content/6/6/2041669515615071.