Procedure

All the photographs were made ready for use with the same process in Stage 1 (black-whiting, placing into the oval frame and smoothing), and the participants (who signed informed consent) evaluated the photographs for neutrality and attractiveness. But, the number of photographs (507 photographs) had prolonged the evaluation process. Therefore, it was difficult to find a volunteer for evaluation. Due to a large number of photographs, most participants quit the study even though they initially volunteered. The data of the participants with incomplete evaluation were not included in the analyses. As a result, all of the photographs were rated by 26 participants. When the data were examined, it was seen that the left symmetrical photographs (this actually corresponds to the right side of the model’s face) tend to be perceived as more attractive by the participants. In addition to the average faces in the set, there should be an equal number of attractive faces as much as possible. As the number of attractive faces in the original and the right symmetrical versions of the photographs is insufficient, Stage 2 was continued with the evaluation of only the left symmetrical versions (169 photographs). In this way, the loss of participants due to the long-term evaluation process was prevented. Thus, all of the photographs in the set consist of the left symmetrical faces. According to the evaluation of 41 new participants, 29% of the 169 photographs were rated as average with a score of 2.5 to 4.5, and 15.4% of them were rated as attractive with a score of 5 or more. Remaining unattractive photographs with a score of less than 2.5 (55.4 % of all photographs) were not included in the face-set due to the ethical concerns mentioned earlier. After excluding unattractive photographs, the distribution of attractive and average photographs was shown by a bar graph in percentiles (Figure 1). All participants evaluated the photographs of both male and female models. No information was obtained about the sexual orientation of the participants. As a result, a total of 52 photographs were selected, including attractive women, attractive men, average women, and average men categories. Examples of photographs of each category are presented in Figure 2.

The percentage distribution of the attractive and average photographs by gender groups

Samples of the male and female photographs of each category in the FaceSet (the approval of the models was obtained).

Although the symmetrical versions of faces considered more attractive than the originals (t(103)= 2.56, p < .05), not all of them are rated attractive (half of the face-set consists of attractive faces) even all of the faces in the set are symmetrical. The finding suggests that only symmetry may not play a role in the perception of attractiveness, and secondary sexual characteristics of the faces in the set (eye width, nasal area width, chin length, etc.) were also be examined. Based on the study of Cunningham (25) and Grammer &Thornhill (26), the secondary facial characteristics of the attractive and average female/male faces were measured using the ImageJ 1.46r software (Figure 3).

The parameters and schematic representation of the secondary sexual characteristics

The parameters of the secondary sexual characteristics: 1) width of eyes (distance between the inner and outer corner of the eye), 2) width of the pupil (ratio of the measured diameter of the pupil to the measured diameter of the iris – width of the face at cheekbones), 3) width of iris (measured diameter – width of the face at cheekbones), 4) width of face at cheekbones (distance between the right and the left of the face at cheekbones), 5) width of the nose (width of nose at outer edges of nostrils at widest point), 6) length of the nose (measured from forehead bridge at level of upper edge of visible eye to nose tip), 7) length of the chin (distance from lower edge of lower lip to base of chin – length of face), 8) width of face at mouth (distance between the right and the left of the face at mouth), 9) length of the face (distance from top of the forehead to base of chin), 10) nose area (the product of the length of the nose and width of the nose – length of the face), 11) cheekbone prominence (difference between the width of the face at the cheekbones, and the width of the face at the mouth –length of the face). A photograph in the FaceSet that approval by the model is used as a background.

All participants who were photographed in the first and second stage of the study have given a written and signed approval for the use of their photographs within the scope of a photo set or face database for scientific purposes.