Increased attractiveness through facial similarity ?

Procedure Participants first underwent an affective startle modulation paradigm, viewing three subsets of pictures of erotic female nudes and standard IAPS neutral pictures while startle eye blink responses to binaural burst of white noise (105 db, 50 ms) were recorded. The erotic female nude pictures were digitally altered, so that the face either resembled the male participant, another participant or were not altered (the last two being the control conditions). After completing the affective startle modulation paradigm, the participants were asked to evaluate each picture for perceived pleasure and arousal using Self-Assessment-Manikin ratings ranging from 1 to 9 (1 indicates very low pleasure and arousal, and 9 very high pleasure and arousal).


Procedure
Participants first underwent an affective startle modulation paradigm, viewing three subsets of pictures of erotic female nudes and standard IAPS neutral pictures while startle eye blink responses to binaural burst of white noise (105 db, 50 ms) were recorded.The erotic female nude pictures were digitally altered, so that the face either resembled the male participant, another participant or were not altered (the last two being the control conditions).After completing the affective startle modulation paradigm, the participants were asked to evaluate each picture for perceived pleasure and arousal using Self-Assessment-Manikin ratings ranging from 1 to 9 (1 indicates very low pleasure and arousal, and 9 very high pleasure and arousal).

Background
Facial similarity is known to induce sympathy and is predicted to increase the prosocial behaviour.However, the effects of similarity on human mating preference remain controversial.While some studies show increased attractiveness ratings for similar faces [1], other studies reach opposite conclusions or show no difference [2].In order to assess the influence of facial similarity on sexual approach motivation we measured eyelid startle response as well as subjective ratings.Therefore, we employed implicit and explicit measures of preference?

Magnitude
Compared to neutral pictures, startle magnitude in the presence of erotic pictures was significantly lower (p < .01).Self-resembling erotic female nudes led to a larger inhibition of the startle reflex compared to other-resembling erotic female nudes (p <. 05) and not manipulated erotic female nudes (p <.05).

Self Report
Analysis of picture valence and arousal ratings revealed a main effect of content (p < .001).All three erotic picture categories were rated to be more pleasant than the neutral pictures (p < .001).However, there was no difference in valence ratings between the three erotic categories (p = 1.00).
Figure 1.Image editing procedure: The nude woman's detailed face (1) was morphed with the portrait picture of the participant (2).The morphing software produces two output images, a shape-only morph (3a) and a combined shape-colour morph (3b).In a second step the shape-colour morph is used as a semi-transparent layer on top of the shape-only morph.All artefacts of the morphing procedure are eliminated.The resulting image (4) was photo-mounted on the woman's body in a last step (5).The resulting image was used as a stimulus (the image was not masked in the experiment).

Cover Story
To be able to morph the participants faces into the faces of the erotic female nudes, we had to gather a standardized photograph of each participant's face.For the nature of the experiment it was necessary that participants did not know about the true purpose of the experiment.To assure this, we used the following cover story: Participants were told that for a payment of 20 € they could participate in two unrelated studies in our lab: The experimenter told participants that the first study was to establish a new emotional face data base that would be used for psychophysiological research in our lab.The second study would analyze emotional and physiological reactions to erotic pictures.Furthermore, the experimenter explained that both studies were run together for economic reasons.

Figure 2 .
Figure 2. T-scored startle magnitude for different stimulus material