We showed that composites (several faces morphed together) are rated generally more attractive by test subjects. But it still remains unclear whether this is due to the averaged proportions of the resulting face (=averageness hypothesis) or whether the skin-smoothing side effect of the morphing procedure causes this increase in attractiveness. 

Therefore, we conducted another experiment: For each three unattractive and three attractive faces of both sexes, we blended their proportions into the average shape by 50%. 
Colour information, i.e. the surface of the face, was kept constant, solely the shape was manipulated. The original as well as the transformed faces were rated for attractiveness by using a two-alternatives forced choice design. 

Examples: 

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Left picture: The prototype of an unattractive female face blended into the shape of the average female face by 50%. The transformed face is rated more attractive than the original (right picture). 
Since the surfaces of both faces were kept constant and only differed in shape, it can be concluded that the proportions of the average female face are rated more attractive than the proportions of the prototypic unattractive face.
 

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Left picture: The prototype of an attractive female face blended into the shape of the average female face by 50%. The transformed face is not rated more attractive than the original (right picture). 
Since the surfaces of both faces were kept constant and only differed in shape, it can be concluded that the proportions of the average female face are not rated more attractive than the proportions of the prototypic attractive face.

The result contradicts the predictions of the averageness hypothesis: The proportions of the average face are perceived as being more attractive compared to the proportions of unattractive faces, but not compared to the proportions of attractive faces. Thus, there are characteristic features that deviate from the average shape (e.g. narrow face, high cheek bones) and might make a face seem more attractive (see also characteristics of beautiful faces!). 

So if it is not the facial proportions that make average faces look more beautiful, then it must be the skin that accounts for the shift in attractiveness. In order to find an answer to that problem, we created two pairs of faces (for each sex), which were identical in their face proportions. By keeping the face proportions constant we could compare different face surfaces (skin) with respect to their attractiveness. We let subjects compare the skin of the average face combined with the proportions of the prototypically attractive face as well as with the prototypically unattractive one (for details see report!) 

It could be shown that it is the young appearing and smooth skin of the computed average faces, which make them so attractive. Interestingly enough, the same applies for male faces. 
 

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In this experiment different facial surfaces were compared with one another keeping their facial proportions constant. 
The difference: The left face has the surface (skin) of the prototypical unattractive face - the right face has the surface of the average face. 
Although the skin of the average face looks much more artificial, it is rated more attractive, probably because the skin looks suntanned and smooth.

Our conducted experiments regarding the shape adaptions of the faces clearly show that it is not the facial proportions but the skin that makes average faces more attractive. Thus, the averageness hypothesis can be refuted with respect to facial proportions!