The spectacular human nose: an amplifier of individual quality?

Background: Amplifiers are signals that improve the perception of underlying differences in quality. They are cost free and advantageous to high quality individuals, but disadvantageous to low quality individuals, as poor quality is easier perceived because of the amplifier. For an amplifier to evolve, the average fitness benefit to the high quality individuals should be higher than the average cost for the low quality individuals. The human nose is, compared to the nose of most other primates, extraordinary large, fragile and easily broken – especially in male-male interactions. May it have evolved as an amplifier, allowing easy assessment of individual quality and influencing the perception of attractiveness? Methods: We tested whether nose tip centrality had a particular influence on attractiveness by manipulating the position of the nose tip or, as a control, the mouth in facial pictures and had the pictures rated for attractiveness. Results: Our results show that facial attractiveness is not influenced by mouth manipulations. Yet, facial attractiveness increased when the nose tip was artificially centered according to other facial features. Conversely, facial attractiveness decreased when the nose tip was displaced away from its central position. Discussion: Our results suggest that the centering of the nose tip is important for evaluation of attractiveness, maybe because it has a particularly strong effect on our perception of facial symmetry or averageness. However, whether such centering is related to individual quality remains unclear.