Abstract
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 among high quality individuals, allowing easy assessment of individual quality and influencing the perception of attractiveness? We tested the latter by manipulating the position of the nose tip or, as a control, the mouth in facial pictures and had the pictures rated for attractiveness. Our results show that facial attractiveness failed to be influenced by mouth manipulations. Yet, facial attractiveness increased when the nose tip was artificially centered according to other facial features. Conversely, attractiveness decreased when the nose tip was displaced away from its central position. Our results suggest that our evaluation of attractiveness is clearly sensitive to the centering of the nose tip, possibly because it affects our perception of the face’s symmetry and/or averageness. However, whether such centering is related to individual quality remains unclear.
Highlights
There is no agreed upon definition of biological communication (Scott-Phillips, 2007), a signal may be defined as any act or structure that has evolved because it alters the behavior of other organisms and this response has co-evolved with signal evolution (Maynard-Smith & Harper, 2003)
Effects on perceived attractiveness were clearly found when the nose was the manipulated feature, while none were found for the mouth manipulations, despite these were of the same magnitude than that used for the nose
The association between attractiveness and nose tip position, but not of mouth position, suggests a bias in perception of the two traits which might be mirrored in the common occurrence of rhinoplasty, mainly occurring among young unmarried women and men (Babuccu et al, 2003)
Summary
There is no agreed upon definition of biological communication (Scott-Phillips, 2007), a signal may be defined as any act or structure that has evolved because it alters the behavior of other organisms and this response has co-evolved with signal evolution (Maynard-Smith & Harper, 2003). It is likely that no single mechanism can explain the enormous variety of signals. Several mechanisms are likely to function simultaneously. There are at least three ways by which signals may be reliable, either by convention, by cost or by design (Hasson, 1990; Hasson, 1997). Signals reliable by convention are cost-free symbols and icons, and have evolved because there exists a mutual interest between signalers and recipients in information transfer (Silk, Kaldor & Boyd, 2000). Signals reliable by cost are costly to produce or maintain and the intensity of the signal strength is proportional to the resources invested in the signal by the
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