Asymmetries for hemiface size and mobility

Determination of Facial Symmetry in Unilateral Cleft Lip and Palate Patients from Three-Dimensional Data: Technical Report and Assessment of Measurement Errors

Objective

To assess measurement errors of a novel technique for the three-dimensional determination of the degree of facial symmetry in patients suffering from unilateral cleft lip and palate malformations.

Design

Technical report, reliability study.

Setting

Cleft Lip and Palate Center of the University of Erlangen-Nuremberg, Erlangen, Germany.

Patients

The three-dimensional facial surface data of five 10-year-old unilateral cleft lip and palate patients were subjected to the analysis. Distances, angles, surface areas, and volumes were assessed twice.

Main Outcome Measures

Calculations were made for method error, intraclass correlation coefficient, and repeatability of the measurements of distances, angles, surface areas, and volumes.

Results

The method errors were less than 1 mm for distances and less than 1.5° for angles. The intraclass correlation coefficients showed values greater than .90 for all parameters. The repeatability values were comparable for cleft and noncleft sides.

Conclusion

The small method errors, high intraclass correlation coefficients, and comparable repeatability values for cleft and noncleft sides reveal that the new technique is appropriate for clinical use.

Importance of the brow in facial expressiveness during human communication

OBJECTIVE

The objective of this study was to evaluate laterality and upper/lower face dominance of expressiveness during prescribed speech using a unique validated image subtraction system capable of sensitive and reliable measurement of facial surface deformation.

RATIONALE

Observations and experiments of central control of facial expressions during speech and social utterances in humans and animals suggest that the right mouth moves more than the left during nonemotional speech. However, proficient lip readers seem to attend to the whole face to interpret meaning from expressed facial cues, also implicating a horizontal (upper face-lower face) axis.

STUDY DESIGN

Prospective experimental design. Experimental maneuver: recited speech.

OUTCOME MEASURE

image-subtraction strength-duration curve amplitude.

METHODS

Thirty normal human adults were evaluated during memorized nonemotional recitation of 2 short sentences. Facial movements were assessed using a video-image subtractions system capable of simultaneously measuring upper and lower specific areas of each hemiface.

RESULTS

The results demonstrate both axes influence facial expressiveness in human communication; however, the horizontal axis (upper versus lower face) would appear dominant, especially during what would appear to be spontaneous breakthrough unplanned expressiveness.

CONCLUSION

These data are congruent with the concept that the left cerebral hemisphere has control over nonemotionally stimulated speech; however, the multisynaptic brainstem extrapyramidal pathways may override hemiface laterality and preferentially take control of the upper face. Additionally, these data demonstrate the importance of the often-ignored brow in facial expressiveness.

LEVEL OF EVIDENCE

Experimental study. EBM levels not applicable.

Three-dimensional gender differences in facial form of children in the North East of England

The aim of the prospective cross-sectional morphometric study was to explore three dimensional (3D) facial shape and form (shape plus size) variation within and between 8- and 12-year-old Caucasian children; 39 males age-matched with 41 females. The 3D images were captured using a stereophotogrammeteric system, and facial form was recorded by digitizing 39 anthropometric landmarks for each scan. The x, y, z coordinates of each landmark were extracted and used to calculate linear and angular measurements. 3D landmark asymmetry was quantified using Generalized Procrustes Analysis (GPA) and an average face was constructed for each gender. The average faces were superimposed and differences were visualized and quantified. Shape variations were explored using GPA and PrincipalComponent Analysis. Analysis of covariance and Pearson correlation coefficients were used to explore gender differences and to determine any correlation between facial measurements and height or weight. Multivariate analysis was used to ascertain differences in facial measurements or 3D landmark asymmetry. There were no differences in height or weight between genders. There was a significant positive correlation between facial measurements and height and weight and statistically significant differences in linear facial width measurements between genders. These differences were related to the larger size of males rather than differences in shape. There were no age- or gender-linked significant differences in 3D landmark asymmetry. Shape analysis confirmed similarities between both males and females for facial shape and form in 8- to 12-year-old children. Any differences found were related to differences in facial size rather than shape.

Asymmetry of the Face in Orthodontic Patients

Objective: To investigate the laterality of the normal asymmetry of the human face, examining differences in laterality in relation to sex, growth stage, and skeletal classification.

Materials and Methods: A total of 1800 Japanese subjects (651 males and 1149 females; mean age, 15 years 3 months; range, 4 years 2 months to 59 years 11 months) were selected. Individuals in the sample were categorized according to sex, one of three growth stages, and one of three skeletal patterns. Differences in length between distances from the points at which ear rods were inserted to the facial midline and the perpendicular distance from the soft-tissue menton to the facial midline were measured on a frontal facial photograph. Subjects with a discrepancy of more than 3 standard deviations of the measurement error were categorized as having left- or right-sided laterality.

Results: Of subjects with facial asymmetry, 79.7% had a wider right hemiface, and 79.3% of those with chin deviation had left-sided laterality. These tendencies were independent of sex, age, or skeletal jaw relationships. In this regard, during pubertal growth, the proportion of subjects with wider right hemiface decreased (P < .0001), whereas the proportion of those with a wider left hemiface increased (P < .01), despite a consistent tendency for right-sided dominance.

Conclusion: These results suggest that laterality in the normal asymmetry of the face, which is consistently found in humans, is likely to be a hereditary rather than an acquired trait.

The role of structural facial asymmetry in asymmetry of peak facial expressions

Asymmetric facial expression is generally attributed to asymmetry in movement, but structural asymmetry in the face may also affect asymmetry of expression. Asymmetry in posed expressions was measured using image-based approaches in digitised sequences of facial expression in 55 individuals, N=16 men, N=39 women. Structural asymmetry (at neutral expression) was higher in men than women and accounted for .54, .62, and .66 of the variance in asymmetry at peak expression for joy, anger, and disgust expressions, respectively. Movement asymmetry (measured by change in pixel values over time) was found, but was unrelated to peak asymmetry in joy or anger expressions over the whole face and in facial subregions relevant to the expression. Movement asymmetry was negatively related to peak asymmetry in disgust expressions. Sidedness of movement asymmetry (defined as the ratio of summed movement on the left to movement on the right) was consistent across emotions within individuals. Sidedness was found only for joy expressions, which had significantly more movement on the left. The significant role of structural asymmetry in asymmetry of emotion expression and the exploration of facial expression asymmetry have important implications for evolutionary interpretations of facial signalling and facial expressions in general.

Nasolabial symmetry following Tennison-Randall lip repair: a three-dimensional approach in 10-year-old patients with unilateral clefts of lip, alveolus and palate

AIM

To assess the degree of facial symmetry in patients suffering from unilateral cleft lip, alveolus and palate (UCLAP) by determining differences between the cleft and the non-cleft hemifaces from 3D surface data.

PATIENTS AND METHODS

In twenty-two 10-year-old UCLAP patients, who had the lip repaired using the Tennison-Randall technique and did not undergo further revisional surgery, differences were determined between landmarks, surface areas of the upper lip vermilion and nostrils and virtual volumes of midface, nose and upper lip for cleft and non-cleft sides, separately, after having established a plane of symmetry calculated from optical 3D facial surface data.

RESULTS

Statistically significant differences could be found between cleft and non-cleft sides for the nasal landmarks G(lat), G(sup) and La(med), the nostril angle and the virtual volume of the nose (p(Glat)=0.011, p(Gsup)<0.0005, p(Lamed)=0.002, p(nostril angle)=0.036 and p(nose volume)<0.0005, resp.).

CONCLUSION

Analysis of 3D data shows that complete nasal symmetry is difficult to achieve with Tennison-Randall's lip repair without revisional surgery. Further trials on larger populations of patients will allow a more comprehensive and consistent analysis of the consequence of different methods for cp repair in order to identify the techniques with the best outcome in terms of facial symmetry.

Detecting hemifacial asymmetries in emotional expression with three-dimensional computerized image analysis

Emotions are expressed more clearly on the left side of the face than the right: an asymmetry that probably stems from right hemisphere dominance for emotional expression (right hemisphere model). More controversially, it has been suggested that the left hemiface bias is stronger for negative emotions and weaker or reversed for positive emotions (valence model). We examined the veracity of the right hemisphere and valence models by measuring asymmetries in: (i) movement of the face; and (ii) observer's rating of emotionality. The study uses a precise three-dimensional (3D) imaging technique to measure facial movement and to provide images that simultaneously capture the left or right hemifaces. Models (n = 16) with happy, sad and neutral expressions were digitally captured and manipulated. Comparison of the neutral and happy or sad images revealed greater movement of the left hemiface, regardless of the valence of the emotion, supporting the right hemisphere model. There was a trend, however, for left-sided movement to be more pronounced for negative than positive emotions. Participants (n = 357) reported that portraits rotated so that the left hemiface was featured, were more expressive of negative emotions whereas right hemiface portraits were more expressive for positive emotions, supporting the valence model. The effect of valence was moderated when the images were mirror-reversed. The data demonstrate that relatively small rotations of the head have a dramatic effect on the expression of positive and negative emotions. The fact that the effect of valence was not captured by the movement analysis demonstrates that subtle movements can have a strong effect on the expression of emotion.

Three-dimensional quantification of the symmetry of normal facial movement

OBJECTIVE

This study examined the right to left symmetry of the displacement of three-dimensional movement of the human face.

METHODS

Displacement data on 42 subjects was collected and analyzed with the Expert Vision Motion Analysis System. Right and left three-dimensional facial displacements were quantified.

RESULTS

Significantly greater left than right three-dimensional displacement across the whole face was measured. The three-dimensional displacement difference ranged from 0.48 mm to 2.28 mm between the right and left sides of the face. The 2-cm inferior pupil markers during the nose wrinkle expression had significantly greater left than right displacement.

CONCLUSION

The ranges of displacement differences, along with the mean three-dimensional displacement measures, must be accounted for in the creation of a baseline of the range of normal facial movement.

Three-dimensional nasolabial displacement during movement in repaired cleft lip and palate patients

The objective of this study was two-fold: (1) to explore the suitability of a novel modified Procrustes fit method to adjust data for head motion during instructed facial movements, and (2) to compare the adjusted data among repaired unilateral (n = 4) and bilateral (n = 5) cleft lip and palate patients and noncleft control subjects (n = 50). Using a video-based tracking system, three-dimensional displacement of 14 well-defined nasolabial landmarks was measured during four set facial animations without controlling for head motion. The modified Procrustes fit method eliminated the contributions of head motion by matching the most stable landmarks of each video-recorded frame of the face during function to frames at rest. Its effectiveness was found to approximate that of a previous method (i.e., use of a maxillary occlusal splint to which stable dentition-based markers were attached). Data from both the unilateral and bilateral cleft lip and palate patients fell outside the normal range of maximum displacements and of asymmetry, and individual patients demonstrated greater right-versus-left asymmetry in maximum displacement than did individual noncleft subjects. It is concluded that the modified Procrustes fit method is fast, is easy to apply, and allows subjects to move the head naturally without the inconvenience of a splint while facial movement data are being collected. Results obtained using this method support the view that facial movements in cleft patients may be severely hampered and that assessment of facial animation should be strongly considered when contemplating surgical lip revisions.

Asymmetry of left versus right unilateral cleft impairments: an experimental study of face perception

OBJECTIVE

Previous psychosocial studies of adults born with cleft lip and palate have provided circumstantial evidence that surgically repaired right-sided unilateral clefts may be more disfiguring than left-sided clefts. The present study asked if such asymmetries are physiognomic asymmetries or arise "in the eye of the beholder," representing perceptual processes in face recognition.

DESIGN

Color slides of 160 children (6 years of age) and young teenagers (16 years of age) were rated by subjects for perceived disfigurement. Sixty of the subjects had unilateral complete cleft lip and palate (30 had a right-sided cleft and 30 had a left-sided cleft), 60 had unilateral cleft lip/alveolus (30 right-sided and 30 left-sided clefts), 32 children had bilateral cleft lip and palate, and 8 children had cleft palate only. Faces were shown in normal and in mirror-reversed versions; the order in which faces were shown was randomized, as were other stimulus factors such as cleft type, age, and gender.

SETTING

The study was conducted as a classroom-type experiment at the Vision Laboratory, Department of Psychology, Oslo, Norway.

PARTICIPANTS

Thirty-seven students of psychology at the University of Oslo, who were ignorant of the purpose of the study, acted as subjects.

MAIN OUTCOME MEASURE

Subjects rated perceived disfigurement using a visual analog scale.

RESULTS

Modest but highly consistent hemifacial asymmetries in judged disfigurement were found, with left-sided unilateral clefts rated as less disfiguring than right-sided unilateral clefts. Unilateral clefts were judged as being less disfiguring than the bilateral clefts, and cleft lip/alveolus was judged as being less disfiguring than cleft lip and palate. The patterns of facial judgments were almost identical in the normal and reversed-slides conditions.

CONCLUSIONS

Asymmetries between left- and right-sided clefts reside in physiognomic factors rather than in hemispheric asymmetries controlling the perceptual process of face judgment.

Neuropsychological aspects of facial asymmetry during emotional expression: a review of the normal adult literature

This review focuses on facial asymmetries during emotional expression. Facial asymmetry is defined as the expression intensity or muscular involvement on one side of the face ("hemiface") relative to the other side and has been used as a behavioral index of hemispheric specialization for facial emotional expression. This paper presents a history of the neuropsychological study of facial asymmetry, originating with Darwin. Both quantitative and qualitative aspects of asymmetry are addressed. Next, neuroanatomical bases for facial expression are elucidated, separately for posed/voluntary and spontaneous/involuntary elicitation conditions. This is followed by a comprehensive review of 49 experiments of facial asymmetry in the adult literature, oriented around emotional valence (pleasantness/unpleasantness), elicitation condition, facial part, social display rules, and demographic factors. Results of this review indicate that the left hemiface is more involved than the right hemiface in the expression of facial emotion. From a neuropsychological perspective, these findings implicate the right cerebral hemisphere as dominant for the facial expression of emotion. In spite of the compelling evidence for right-hemispheric specialization, some data point to the possibility of differential hemispheric involvement as a function of emotional valence.

Laterality in facial expressions and its effect on attributions of emotion and personality: a reconsideration

Are there consistent differences between the emotions attributed to the right and left hemiface? Six studies investigated this old question, using a new technique of computerized image reconstruction that eliminates several confounding factors common in previous studies. Findings suggest that there are no consistent differences between the emotions and personality attributed to the right and the left hemiface. Nevertheless, when the two hemifaces were simultaneously compared on intensity, the left hemiface showed greater intensity in posed smiles. As a whole, the present study suggests the possibility of a slight inference of brain laterality in posed expressions, but not in resting faces.

Facial asymmetry in partial epilepsies

Fifty-six consecutive epileptic patients with partial seizures (30 temporal, 26 extratemporal) and facial asymmetry were studied. Facial asymmetry was compared with EEG, radiologic, and other clinical findings. Thirty patients had a lesional epilepsy whereas 26 were considered cryptogenic. In lesional epilepsies, 60% of patients had EEG foci ipsilateral to the smaller hemiface and only 20% had EEG foci contralaterally. In the cryptogenic group, the EEG focus was ipsilateral in 50% and contralateral to the facial smallness in 46%. No differences were noted between temporal and extratemporal epilepsies. Early acquired cerebral lesions may modify development of the hemisphere involved, leading to a small ipsilateral hemiface and seizures originating from the same side.

Spontaneous facial expression of emotions in brain-damaged patients

Spontaneous facial expression of emotion was studied in two groups of right (N = 23) and left (N = 39) brain-damaged patients and in a control group of normal subjects (N = 28). To elicit emotions four short movies, constructed to produce positive, negative or neutral emotional responses, were used. The method used to assess the facial expression of emotions was the Facial Action Coding System. Brain-damaged patients showed less facial responses to emotional stimuli than normal controls, but no difference was observed between subjects with right and left-sided lesions either with global or disaggregated data analyses, inconsistent with the hypothesis of a specialization of the right hemisphere for facial emotional expressions. An unexpected difference was observed in response to the unpleasant movie. Both normal controls and left brain-damaged patients often averted their gaze from the screen when unpleasant material was displayed, whereas right brain-damaged patients rarely showed gaze aversion. This finding suggests that the degree of emotional involvement or manner of coping with stressful input may be reduced as a result of right brain damage.

Emotional and non-emotional facial behaviour in patients with unilateral brain damage

Aspects of emotional facial expression (responsivity, appropriateness, intensity) were examined in brain-damaged adults with right or left hemisphere cerebrovascular lesions and in normal controls. Subjects were videotaped during experimental procedures designed to elicit emotional facial expression and non-emotional facial movement (paralysis, mobility, praxis). On tasks of emotional facial expression, patients with right hemisphere pathology were less responsive and less appropriate than patients with left hemisphere pathology or normal controls. These results corroborate other research findings that the right cerebral hemisphere is dominant for the expression of facial emotion. Both brain-damaged groups had substantial facial paralysis and impairment in muscular mobility on the hemiface contralateral to site of lesion, and the left brain-damaged group had bucco-facial apraxia. Performance measures of emotional expression and non-emotional movement were uncorrelated, suggesting a dissociation between these two systems of facial behaviour.

Left-sided oral asymmetries in spontaneous but not posed smiles

To investigate possible facial asymmetries during the production of posed and spontaneous smiles, the displacement of various reference points on the mouth were measured as subjects produced both kinds of smiles. Strobe cameras were used in combination with a computer-based analysis to record the smiles of left- and right-handed males and females. The analysis revealed that the left side of the mouth moved more than the right side during spontaneous but not posed smiles, supporting the notion that the right hemisphere may play a special role in emotional expression. This asymmetry was most apparent in left-handed females and right-handed males. These sex and handedness differences are discussed with reference to apparent inconsistencies in previous research on asymmetries in emotional expression.

Morphologic asymmetries of the face: a review

It has been suggested that asymmetries in the morphological properties of the face contribute to or produce asymmetries in facial emotional expression. Over 50 years of research on hard tissue, soft tissue, and facial surface asymmetries is reviewed here. Generally, it appears that if consistent asymmetry characterizes facial morphology, it is extremely small in magnitude or characterizes regions yet to be examined. In contrast, marked homology and asymmetry in regional size and area has been noted often. At present, it does not appear that asymmetry in facial morphology is associated with facial expressive asymmetry, with the latter more likely to be an outcome of functional brain asymmetry.

Right brain, left brain; left face, right face: hemisphericity and the expression of facial emotion

Research on the asymmetry of facial expressions is reviewed in terms of neuroanatomy, qualitative and quantitative measures of asymmetrical expression, method of expression elicitation (spontaneous, posed, imagery-based), type of expression (happy, sad, etc.), and expression rating procedures. Neuroanatomical evidence indicated that contralateral control of facial musculature exists only for the lower face and that different motor pathways are responsible for spontaneous versus posed expressions. Empirical research on the differential assignment of qualitative trait attributes to facial regions was judged to be meagre and data on quantitative differences in the asymmetry of facial expressions was inconclusive because of the wide variability in methodology across past investigations. Specific suggestions for future investigations in this area are offered and alternative conceptualizations of hemisphericity and facial asymmetry proposed.

Development of hemiface size asymmetry

Facial size asymmetries for the upper and lower face were measured from photographs of 40 neonates (3 days old), 40 preschoolers (2-4 years), and 40 young adults (18-24 years), approximately equally divided by sex. The right hemiface was significantly larger than the left in the three age groups, and there were no differences in the distributions of asymmetry as a function of age.

Asymmetry of facial expression in spontaneous emotion

The observation that emotional expressions are more intense on the left side of the face is consistent with other evidence of the importance of the right hemisphere in emotional communication. However, the question has been raised whether it is truly spontaneous emotional expressions or only posed facial displays that show a left-sided asymmetry. We surreptitiously examined facial asymmetry during spontaneous emotional expressions as subjects remembered happy or sad experiences. These were contrasted with the subjects' posed expressions of happy or sad emotions. Both of these procedures resulted in more intense expressions on the left side of the face. The left-sided advantage was stronger during the spontaneous than the posed displays, and was observed for both happy and sad emotions.

Hemiface mobility and facial expression asymmetry

Thirty-seven right-handed college-aged males and females were assessed for facial asymmetry during emotional expression and for nonemotional hemiface mobility. Objective, subjective, and undirected measures of facial mobility were obtained, separately for the upper and lower face. While judges rated mobility of the lower face as left-sided, subjects declared themselves to be as facile on the right as on the left side of the face. When asked to move a side of the lower face, subjects moved the right side more frequently than the left. For the upper face, none of the measures of mobility were significantly left- or right-sided. Facial expression asymmetries (which were observed to be left-sided) were not significantly related to any measures of hemiface mobility.

Is there a bias in size measurements taken from mirror-reversed photographs of body parts?

This study compared measurements of hands, feet, and hemifaces taken from original and mirror-reversed photographs to determine whether a hemispace-bias exists in size measurements. Posers were adult right- and left-handers (50% female). In 80% of the measurement comparisons (total N = 84), there was complete agreement; there were no instances of right-left reversals among the discrepant comparisons. The side of the body measured as larger was independent of the side of space in which it appeared. The lack of such bias in physical measurements is discrepant with data suggesting a left-hemispace preference in psychological judgments of visual material.

Facial asymmetry in posed and spontaneous expressions of emotion

Patterns of facial asymmetry (i.e., extent of movement) as a function of elicitation condition, emotional valence, and sex of subjects are examined. Thirty-seven right-handed adult males and females were videotaped making positive and negative expressions of emotion under posed (verbal, visual) and spontaneous conditions. There were no differences in facial asymmetry as a function of condition. Overall, expressions were significantly left-sided, a finding implicating the right hemisphere. When sex and valence were considered, negative expressions were left-sided for all subjects, while positive expressions were left-sided for males only. Further, positive expressions were significantly less lateralized than negative ones for females. Measures of hemiface mobility and ocular dominance did not mediate these patterns of facial lateralization.