Oral Maxillofac Surg DOI 10.1007/s10006-014-0441-x

ORIGINAL ARTICLE

Panel perception of facial appearance of cleft patients generated by use of a morphing technique Vedat Yildirim & Alexander Hemprich & Martin Gründl & Niels Christian Pausch

Received: 9 September 2013 / Accepted: 8 January 2014 # Springer-Verlag Berlin Heidelberg 2014

Abstract Objective Perception of the facial appearance of cleft patients has, until now, been evaluated on the basis of photographs of the patients. Research based on photographs generated by use of a morphing technique has not yet been reported. The purpose of this study was to investigate female and male raters’ panel perception with regard to the following: (1) patient age, (2) attractiveness, (3) gender appearance, and (4) likeability of faces of cleft patients generated by the use of a morphing technique. Setting The study was conducted at the Department of Oral, Craniomaxillofacial and Facial Plastic Surgery, University Hospital of Leipzig, Germany. Patients, participants We used photographs of 32 adult German nonsyndromic cleft patients, mean age 18.9±1.3 years, and surveyed 93 students, mean age 25.3±3.2 years, by use of a standardized questionnaire. Results All respondents rated the mean age of cleft patients equally in unmorphed and morphed pictures. For all respondents, attractiveness of morphed patient pictures was rated significantly higher than for unmorphed pictures (mean 4.8± 1.0 vs. 6.4±2.4; p<0.001), although significance was reached only if morphed pictures of eight patients were rated. Female respondents rated attractiveness significantly higher than did males, especially for pictures of female patients. Presented at the 12th International Congress on Cleft Lip/Palate and Related Craniofacial Anomalies, May 5–10, 2013, Orlando, Florida, USA V. Yildirim (*) : A. Hemprich : N. C. Pausch Department of Oral, Craniomaxillofacial and Facial Plastic Surgery, Faculty of Medicine, University Hospital of Leipzig, Liebigstr. 12 04103, Leipzig, Germany e-mail: [email protected] M. Gründl Institute for Psychology, University of Regensburg, Regensburg, Germany

Conclusion Facial morphing of patient pictures is a suitable method for creation of standard cleft faces. Despite the modification of the pictures, the faces generated remain human and assessable by panel members. Perception of faces of cleft patients’ depended on raters’ gender. Keywords Morphing . Perception of faces . Cleft lip palate

Introduction One the most common visible birth defects are orofacial clefts (cleft lip with or without cleft palate), which occur in 1 of every 500–1,000 live births worldwide [1]. They are the most stressful for patients and parents. With a prevalence of 9.92 per 10,000 births, orofacial clefts are among the most frequent congenital craniofacial deformities [2]. Treatment of these deformities requires several medical disciplines and often takes many years. Since the dawn of time, human faces have been of vital importance for communication and establishing contacts. Perception of faces is thus important and is the result of a complex cognitive process in specific areas of the brain [3]. Appearance, symmetry, and expression affect perception [4, 5]. In many cultures, attractive and symmetrical faces are extremely important for positive perception, and it has been shown that attractiveness and facial symmetry are closely related [6]. That negative impression of facial appearance effects private and professional outcomes has also been proved [7–9]. Studies show that most cleft patient faces lack attractiveness and symmetry [10], and the lack of these characteristics is a disadvantage to cleft patients in social integration. Macgregor showed that psychological problems are associated with facial deformities [11]. Subsequent studies showed that patients with facial deformities, for example cleft patients, suffer from social discrimination [12, 13], and a substantial

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number of patients reported they had been teased because of their cleft [9, 14, 15]. Even today, animal terms (i.e., harelip) are used to label oral cleft deformity [16]. This discrimination against cleft patients begins in early childhood and continues throughout life. According to Noar et al., cleft patients are, in general, satisfied with their overall facial appearance, but some individual facial features, for example nose, lips, profile, and smile, may cause dissatisfaction [17]. Little is known about the relationship between cleftcaused changes and social discrimination. How the faces of cleft patients are perceived is currently the subject of investigations [18]. As mentioned above, symmetry is important to positive perception of faces. After cleft rehabilitation, most asymmetry occurs in the midface of cleft patients, and a high percentage of patients were dissatisfied with their facial appearance [19]. There are significant differences between the perception of facial aesthetics by professionals and lay people [20]. Since the 1990s, processing of human faces and analysis of perception of faces have been the subject of much empirical work. One possibility is to use photographs of individual faces for assessment. The use of these photographs to analyze perception of faces is, in general, possible but has the flaw of being individually very subjective [21]. For most of these psychological studies, therefore, researchers have generated artificial faces, by use of several techniques. In some studies, facial attractiveness has been analyzed by use of generated composite faces and comparison of these with the faces used to create them [22]. More recently, morphing has been used to generate composite faces [23–25]. In 2010, Hamilton suggested morphing images to demonstrate potential surgical outcomes [26]. Some authors have analyzed whether perception of composite faces can be categorized [27]. As a result of work by the film industry, in 1992, the basic technique for 2D images was first described [28]. This technique has subsequently been broadened to enable the creation of 3D human head models [29]. Most studies on the perception of faces of cleft patients have used photographs of cleft faces [10, 21]; faces generated by morphing have not previously been used. In our study, we investigated perception of the faces of cleft patients by using images of faces created by use of a morphing technique and comparing these with unmorphed images of cleft individuals. The purpose of this study was construction of an average cleft face with typical cleft characteristics and without details which might distract the assessor. Known issues in the evaluation of images, for example distraction by individual characteristics (skin texture, hair), would be avoided. We wished to determine whether morphed images were useful for further analysis, for example perception studies and planning surgical outcome, and whether they are as assessable as photographs by a panel.

Material and methods Patients In our study, we used photographs of 32 adult German nonsyndromic cleft patients. Two groups were formed: group I: 16 adults (eight females (mean age 20.1±4.2 years) and eight males (mean age 17.3±0.7 years)) aged 16–27 years (mean age 18.7±3.2 years) with a complete unilateral cleft lip palate (UCLP) and group II: 16 adults (eight females (mean age 18.5±4.4 years) and eight males (mean age 19.9±4.9 years)) aged 14–30 years (mean age 19.2±4.6 years) with a complete bilateral cleft lip palate (BCLP). All patients were treated at the Department of Oral, Craniomaxillofacial, and Facial Plastic Surgery of the University Hospital of Leipzig between 1995 and 2012. Primary cleft rehabilitation was complete for all the patients included. Patients with severe facial asymmetry were excluded because of severe distortion during the morphing procedure. To make the cleft patients as homogeneous as possible, other exclusion criteria were syndromic clefts and those for whom secondary cleft lip nose correction had been performed. Participants gave written informed consent after the study had been explained to them in full detail. The study was approved by the Ethics Committee of the University of Leipzig and was conducted in accordance with relevant institutional and national regulations and legislation and in accordance with the World Medical Association Helsinki Declaration as revised in October 2008. Respondents The pictures were rated by 93 dental student volunteers (52 females and 41 males), mean age 25.3±3.2 years, from Leipzig, Germany. Generating facial morphs Facial morphs of the patients were created by use of digital image-morphing software (MorphMan 4.0; STOIK Imaging Ltd, Moscow, Russia) as described elsewhere [30, 31]. Morphing is a special effect that coalesces one image with another. By marking key points on one face, for example the contours of the nose, lips, and ears or the location of the eyes, and marking the positions of these same points on the other face, the software distorts the first face to give it the shape of the second face at the same time as it fades the two faces. The contours of the source and destination pictures become overlapped. If there is little difference between the source and destination pictures, realistic facial morphs are obtained. The morphing algorithm uses the steps of warping, tweening, and cross-dissolving. Warping is the first morphing algorithm and causes the drawing and extending of the picture

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[32, 33]. Every point in the source picture is given a new one in the destination picture. The new position depends on marked picture elements selected and on subsequently labeled pairs of reference lines. The second morphing algorithm uses tweening. By tweening, calculated points are converted by linear interpolation from the source picture into a new position. The last part of morphing is cross-dissolving or “color morphing.” Red, green, and blue (RGB) values for each pixel are linearly interpolated and mixed. Tweening and crossdissolving occur simultaneously. Every morph consists of at least two pictures (frontal/ profile); Fig. 1 depicts the genesis of a two-morph and a final eight-morph in frontal and profile views. Pictures 1 and 2 show two different BCLP patients. Picture 3 shows the morphed picture from these two patients; this is a twomorph picture. Picture 4 shows the final eight-morph obtained from patients 1 and 2 and six more BCLP patients. Two twomorphs can be combined to create a four-morph picture, and two four-morphs can be mixed to create an eight-morph picture. Accordingly, an eight-morph consists of pictures of eight patients (Fig. 2).

Picture rating task Thirty-two frontal and profile photographs of cleft patients (16 female (eight UCLP, eight BCLP); 16 male (eight UCLP, eight BCLP)) were selected for the survey, and two, four, and eightmorphs were created as described above. Four eight-morphs,

Fig. 1 Genesis of a two-morph and the final eight-morph in frontal and profile views

two four-morphs, two two-morphs, and two reference pictures of noncleft subjects were assembled for presentation. As reference, we used two morphs of our patients’ ages created from noncleft healthy persons (one female, one male, frontal and profile). The female face consisted of the faces of 64 females aged 17–30 years (mean age 23.3 years); the male face consisted of those of 32 males aged 21–30 years (mean age 25.1 years); these faces were from the study “Beautycheck” [34]. For rating, a Beamer PowerPoint presentation was prepared and shown to the respondents (details described above). The respondents rated the pictures in the context of a questionnaire. The authors developed a standardized, encoded, ratioscaled questionnaire. Panel options were the following: 0= very attractive vs. 10=not attractive, 0=masculine vs. 10= feminine, and 0=likeable vs. 10=unlikable. Frontal and profile photographs obtained from the 32 cleft patients were divided into eight UCLP female/male and eight BCLP female/male. Eight pictures were shown on each PowerPoint page (frontal and profile). Every page of the presentation was shown to the respondents for 20 s. The respondents were requested to give average values for age, attractiveness, gender specificity, and likeability for the eight pictures. They then viewed the morphed and unmorphed pictures and were asked to rate the age, and the attractiveness, gender specificity, and likeability of every face on a scale from 0 (very attractive, masculine, and likeable) to 10 (not attractive, feminine, and unlikable). During the presentation, the pictures appeared in random order, and the respondents were

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Fig. 2 Flow chart showing morphing sequence for patient pictures

not told whether an unmorphed face or one of the different morphs was being shown. Statistical analysis Differences between groups were assessed by use of the nonparametric Mann–Whitney U test or the Wilcoxon test. All statistical analyses were performed by use of SPSS 15.0 software. p values less than 0.05 were regarded as indicative of statistical significance. All variables were expressed as mean ± standard errors.

by use of the morphing technique as greater than that of unmorphed pictures. In detail, morphs created from only two (mean 6.0±1.2) or four (mean 5.8±1.5) individual pictures were rated equal to unmorphed pictures whereas morphs created from eight (mean 4.6±1.2) pictures were rated significantly (p<0.001) more attractive than unmorphed pictures. The two reference morphs were rated more attractive than all the other morphs (mean 1.9±0.8) (Fig. 3). Female respondents tended to rate the attractiveness of the pictures significantly higher than did male respondents (Figs. 3 and 4). For example, females rated unmorphed pictures of the faces of cleft patients as significantly more attractive than did male respondents (mean 5.7±1.1 vs. 7.4± 6.3; p<0.001); also, morphed pictures of patients were rated slightly more attractive by female respondents than by male respondents, although the difference was not significant (mean 4.6±0.9 vs. 5.1±1.1). Subanalysis revealed the interesting fact that female respondents rated facial morphs of female patients significantly more attractive than did male respondents (mean 4.9±0.9 vs. 5.7±1.2; p=0.001) (Fig. 4). Subanalysis also showed that female respondents rated morphs of female UCLP and BCLP patients as significantly more attractive than did male respondents (mean 3.9± 1.0 vs. 4.8±1.3; p=0.001 (UCLP); mean 5.6±1.1 vs. 6.3± 1.5; p=0.009 (BCLP)) (not shown). Rating of patients’ gender appearance Analysis of results for both groups revealed no difference between gender-specific rating of appearance.

Results

Rating of patients’ likeability

All 93 questionnaires were included in the study. There was no dropout for any reason.

The ratings for likeability were similar to those for attractiveness. Female and male respondents rated likeability for morphed patient pictures significantly higher than for unmorphed pictures (mean 4.1±1.0 vs. 4.8±1.0; p=0.004 (male); mean 3.8 ± 1.0 vs. 4.6 ± 1.0; p< 0.001 (female)). Unmorphed pictures of faces, and morphs created from two or four individual pictures of the faces of cleft patients, were rated equally. Morphs created from pictures of the faces of eight patients were rated significantly more likeable than unmorphed pictures or pictures morphed from two or four pictures (mean 3.9±1.1 vs. 4.8±1.0 vs. 4.8±1.3 vs. 4.9±1.4) (Fig. 5). Similarly to attractiveness, it was apparent that female respondents tended to rate likeability with the pictures (morphed and unmorphed) significantly more highly than did male respondents. Moreover, in comparison with attractiveness, female respondents rated morphed pictures of female (mean 3.9±1.1 vs. 4.6±1.0; p=0.001) and male (mean 5.1± 1.2 vs. 4.4±1.3; p=0.009) patients as significantly more likeable (Fig. 6). The UCLP patients (female and male) were also

Rating of patients’ ages All respondents rated mean age of unmorphed and morphed pictures of cleft patients equally (mean 22.9±2.4 vs. 22.2±2.3). There was also no difference between detailed analysis of female and male respondents (22.8±2.4 vs. 23.0±2.5). The two reference morphs were also rated equal in age (22.9±2.3) compared with all the patient morphs. The only difference we found was for the mean ages of unmorphed male patients with BCLP. These were rated higher than the ages of unmorphed female patients with BCLP (24.8±3.2 vs. 21.7±3.4), but the difference was not significant. Rating of patients’ attractiveness All respondents significantly (mean 4.8±1.0 vs. 6.4±2.4; p<0.001) rated the attractiveness of patient pictures generated

Oral Maxillofac Surg Fig. 3 Results from rating of attractiveness by female and male respondents

rated significantly more likeable by female respondents than by male respondents (mean 3.0±1.2 vs. 4.0±0.9; p=0.001); no difference was observed for the BCLP patients (not shown). Complete results are not shown, but are available on request.

Discussion The purpose of this work was to determine whether the morphing technique is suitable for study of perception of cleft patients’ faces and whether facial perception depends on raters’ gender. Pictures of cleft patients generated by morphing were, therefore, evaluated with regard to patient age, attractiveness, and gender appearance, and likeability with the patient. In addition, the effect on perception ratings of cleft location, gender of the cleft patients, and number of facial pictures used to create the morph was investigated. Our results showed that attractiveness and likeability ratings for pictures of faces generated by the morphing technique were higher than those for unmorphed pictures, although the difference was significant for eight-morph patient pictures

only. Further, it was apparent that ratings for noncleft controls were better than those for cleft patients or cleft morphs and that these results were gender-specific. Female respondents tended to rate attractiveness and likeability more positively than male respondents. The tendency for females to observe facial attractiveness differently from males is known from previous studies [35]. Our findings are in agreement with some of these previous findings; for example, females generally tended to rate targets as more attractive than did male participants. There may be different reasons for this effect. Same-sex solidarity, reduced social distance, or charity for cleft patients could be underlying aspects. Jones et al. found that women’s preferences for femininity in both male and female faces changed during the menstrual cycle [36]. Other authors suggest that females are more tolerant than men of facial distortion [37]. We assume that elements of socialization, for example compassion and liking other people, are present to a greater extent in females than in males. If the assessed images show patients with facial anomalies, commiseration is probably stronger than intersexual competitive behavior. However, to conclude, this rating tendency is female-specific and does not depend on morphing

Oral Maxillofac Surg Fig. 4 Comparison of ratings of attractiveness by female and male respondents

technique because female respondents rated morphed and unmorphed pictures of patients’ faces more attractive than did male respondents (Fig. 4). Our study showed there was no difference between rating of gender appearance (feminine or masculine). Female and male respondents in both groups rated gender appearance equal. So, we can assume that attractiveness is not affected by the gender appearance of patients. It could be claimed that young age is often connected with greater attractiveness, but our results showed there was no difference between evaluation of the ages of cleft patients in morphed and unmorphed pictures. So, we can say that patient age also had no effect on rating of attractiveness in our study. The ratings for likeability were similar to those for attractiveness. These results suggest that attractiveness is linked with likeability. Data exist that imply a correlation between likeability and attractiveness; the correlation was 0.9 for female faces and 0.81 for male faces, which confirms our findings [34]. We are aware that there is a fluid border between “attractive” and “likable.” The “beautiful is good” stereotype is omnipresent in society [4, 38]. An attractive face is not

necessarily likable, however. It might also appear arrogant or express other negative characteristics. That is why we investigated likeability and attractiveness as separate characteristics. Our findings confirm, however, the experience that young people do judge a book by its cover and associate a beautiful face with positive aspects. Several studies have shown that general judgment of the attractiveness of a face is affected by such details as, for example, hair, eyes, nose, or lips [39]. Some authors have, therefore, used the technique of masking or removing facial areas to reduce the effect of the surrounding facial features [40]. This modification may depersonalize and distort the faces investigated. Such problems can be avoided by use of the morphing technique. Another problem of conventional cleft face perception studies is that most investigations have used pictures of the faces of individual cleft patients. It is clear that every face of a cleft patient has its individual characteristics, so ratings are very subjective. The morphing technique offers the promising possibility of making photographs look more average which can reduce the subjectivity of assessment of images of the face.

Oral Maxillofac Surg Fig. 5 Results from rating of likeability by female and male respondents

Although our study was carefully prepared and planned, we are aware of its limitations. First, we included only respondents of similar age (21–34 years, mean 25.3±3.2 years) and similar background, so our respondents’ ratings do not reflect those of the general population. It would be interesting in further studies to investigate the effect of respondents’ age on rating tendencies. Second, the use of PowerPoint to present the pictures might negatively affect rating results, because of respondents’ different individual levels of concentration. Perhaps the defined time window of 20 s per picture is too short for respondents who need more time to register a face yet too long for respondents who decide quickly and therefore become bored. We also suspect that very long presentation of the pictures reduces the ability of the respondents to concentrate. In 1992, Reynolds and Pezdek showed that participants remembered faces exposed for 20 s significantly better than faces exposed for 3 s [41]. In our study, therefore, we decided to show every page of the presentation to the respondents for 20 s. The respondents could also be influenced by their neighbors. We observed some respondents discussing the pictures

with their neighbors during the presentation. However, PowerPoint presentation with a defined time window ensures that respondents’ ratings are based on their first impression, as intended. Finally, the morphing technique itself might affect our results negatively. It is known that the morphing technique generates faces which are more symmetric than unmorphed faces [25]. Some authors believe symmetry is extremely important for positive perception of faces [42], and therefore, one can suppose that morphed faces tend to be rated more positively than unmorphed faces. Recent studies, however, have shown that symmetry is not automatically linked with greater attractiveness [5, 34]. With regard to the special situation of cleft patients, it is obvious that symmetry does not guarantee attractiveness. Bilateral clefts, which are often symmetric, may detract significantly from facial appearance whereas attractive patients with unilateral clefts may have remarkable asymmetry in their face. As a result of the limitations of the morphing procedure, we concede that morphing of faces of cleft patients is not suitable for planning individual therapy in surgery

Oral Maxillofac Surg Fig. 6 Results from rating of likeability for morphed and unmorphed pictures of cleft patients

for secondary correction. Computer-aided cleft-simulation surgical systems are more suitable for this purpose [43, 44]. However, images, whether morphed or not, are simply images. As mentioned above, there are many diagnostic and treatment planning image techniques, but the underlying foundation of successful cleft lip/nose palate surgical correction is inextricably linked to accurate and adequate surgical reconstitution of the relevant anatomical structures and physiological function. Planning of individual therapy must be designed to meet the needs and wishes of every cleft patient. Morphing of the faces of cleft patients remains an experimental tool for visualization of the averaged facial characteristics of cleft patients.

Conclusion The faces of cleft patients are very variable and consist of numerous individual characteristics, which can affect our perception. Morphing reduces individual distracting details. What remains is what concerns and unites all cleft patients, namely the stigma of the scar and the

typical disfigurement of lip and nose. These characteristics of a cleft physiognomy are smoothed, but still present, after morphing. This unification offers new options for evaluation of the faces of cleft patients. As the individual features associated with the cleft disappear further into the background, the face becomes more average. By this means, cleft faces can be evaluated as a group in studies without these influencing factors. Our study has demonstrated that perception of cleft faces very much depends on the gender of the respondents, the location of the cleft, and patient gender. Morphed faces were rated more positively in our study. Women, here, are somewhat less critical than men, a phenomenon which is also known from ranking of attractiveness unrelated to malformation. The morphing technique is suitable for study of perception of cleft physiognomy; the modified photographs remain real and assessable. We are aware of the limitations of the technique and do not claim to have found the ideal tool for investigation of cleft patients’ faces. We believe this experimental approach has much potential for further development, however.

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