Perception Of Smile Research Articles

Spatial and Temporal Linearities in Posed and Spontaneous Smiles

Creating facial animations that convey an animator’s intent is a difficult task because animation techniques are necessarily an approximation of the subtle motion of the face. Some animation techniques may result in linearization of the motion of vertices in space (blendshapes, for example), and other, simpler techniques may result in linearization of the motion in time. In this article, we consider the problem of animating smiles and explore how these simplifications in space and time affect the perceived genuineness of smiles. We create realistic animations of spontaneous and posed smiles from high-resolution motion capture data for two computer-generated characters. The motion capture data is processed to linearize the spatial or temporal properties of the original animation. Through perceptual experiments, we evaluate the genuineness of the resulting smiles. Both space and time impact the perceived genuineness. We also investigate the effect of head motion in the perception of smiles and show similar results for the impact of linearization on animations with and without head motion. Our results indicate that spontaneous smiles are more heavily affected by linearizing the spatial and temporal properties than posed smiles. Moreover, the spontaneous smiles were more affected by temporal linearization than spatial linearization. Our results are in accordance with previous research on linearities in facial animation and allow us to conclude that a model of smiles must include a nonlinear model of velocities.

The perception and mimicry of facial movements predict judgments of smile authenticity.

The mechanisms through which people perceive different types of smiles and judge their authenticity remain unclear. Here, 19 different types of smiles were created based on the Facial Action Coding System (FACS), using highly controlled, dynamic avatar faces. Participants observed short videos of smiles while their facial mimicry was measured with electromyography (EMG) over four facial muscles. Smile authenticity was judged after each trial. Avatar attractiveness was judged once in response to each avatar’s neutral face. Results suggest that, in contrast to most earlier work using static pictures as stimuli, participants relied less on the Duchenne marker (the presence of crow’s feet wrinkles around the eyes) in their judgments of authenticity. Furthermore, mimicry of smiles occurred in the Zygomaticus Major, Orbicularis Oculi, and Corrugator muscles. Consistent with theories of embodied cognition, activity in these muscles predicted authenticity judgments, suggesting that facial mimicry influences the perception of smiles. However, no significant mediation effect of facial mimicry was found. Avatar attractiveness did not predict authenticity judgments or mimicry patterns.

Effect of Changes in Divine Proportion on Esthetic Perception of Smile in Frontal View

In orthognathic surgery, the surgeon is capable of creating new dimensions to the patient's face. Because a beautiful smile could be related to the divine proportion, the purpose of the current study was to evaluate the changes in the perception of smile after approximating some components of smile to the divine proportion orthodontically or surgically. Ten 20- to 25-year-old women with pleasant smiles and no obvious malocclusions participated in this study. Five standard photographs were taken from each participant in a posed smile, and the most natural one was selected and scanned into black and white pictures. Ten anthropometric landmarks were detected on each image and 10 ratios including Labial inferioris (Li)/right chelion (RCh)-right antegonion (RAgo), subnasale (Sn)-Li/left chelion (LCh)-left antegonion (LAgo), RCh-RAgo/labial superioris (Ls)-Li, LCh-LAgo/Ls-Li, Ch-Ch/Ls-Li,stomion (St)-Sn/St-Li, the maxillary central incisor width/maxillary centralincisor height, Ls-right cuspid (RCus)/RCh-RCus, Ls-left cuspid (LCus)/LCh-LCus, and LCus-RCus/Ch-Ch were measured on each picture. The numerators or denominators of the mentioned ratios were then changed in a way that mentioned the divine proportion (1/1.618) was approximated. All the 110 pictures were evaluated by 40 judges in 2 sessions using a visual analog scale. Intraclass correlation coefficient was also calculated (single measure, 0.644; F = 26.27; P < 0.001). The level of significance for this study was P = 0.05. The tests used to analyze the data were general linear model, the Friedman, and Wilcoxon tests. This study showed that LCus-RCus/Ch-Ch, Ls-Lcus/LCh-Lcus, and Ls-RCus/RCh-RCus (with mean scores of 64.2, 57.2, and 56.1, respectively) had the most positive effects on the esthetic perception of smile. However, RCh-RAgo/Ls-Li with a mean score of 29.1 and LCh-LAgo/Ls-Li with a mean score of 24.5 had the mostnegative effects. There were significant differences among the variables with each other except for A0 to J0 and A6 to J6 (F = 450.6; P = 0.001). Approximating the ratio RCus-LCus/Ch-Ch to the divine proportion may definitely help in achieving a more pleasant smile. On the next level, altering the ratios Ls-LCus/LCh-LCus and Ls-RCus/RCh-RCus could also play a role in making a beautiful smile.

Perceptions of dental professionals and laypeople to altered dental esthetics in cases with congenitally missing maxillary lateral incisors

BackgroundThe smile perception of patients is not strictly related to standardized protocols and technical implications which certainly affect clinicians' decisions. The absence of maxillary lateral incisors could affect smile esthetics either with treatment or not. The aim of the present study was to investigate if different perceptions on altered smiles due to missing maxillary lateral incisors, with or without treatment, exist among different groups of people (laypersons, adult orthodontic patients, general dentists, and orthodontists).MethodsAn ideal smile model was selected and altered simulating different malocclusions and treatment options. Twelve simulations were submitted to four categories of respondents: laypeople, adult orthodontic patients, general dentists and orthodontists. They were asked to express smile perception for each simulation by ranking and rating simulations using a 0 to 100 visual analog scale. Analysis of variance was used to determine if there were statistically significant differences in values assigned among the four categories of respondents for each simulation.ResultsSignificant differences in smile perceptions were found between professionals (dentists and orthodontists) and laypeople. Presence of dental tipping and marked diastema in the arch were disharmonious aspects less tolerated in a smile by all categories of evaluators. Simulations associated with space closure orthodontic treatment were ranked as the most attractive smile and significantly ranked higher by dental professionals than patients and laypeople.ConclusionsTreatment, absence of diastema, and symmetry were the most accepted characteristics by all categories of respondents. Ideal orthodontic treatment options might be overestimated by clinicians when compared to laypeople's smile perception.

Turning subjective into objective: Profile smile perception of I2(incisor inclination) and its impact on treatment planning

Objectives: (1) To evaluate the impact of maxillary incisor inclination on the aesthetics of the profile view of a smile, (2) to determine the most aesthetic inclination in the profile view of a smile and correlate it with facial features and (3) to determine whether dentists, orthodontists and laypeople appreciate differently the incisor inclination in smile aesthetics. Materials and Methods: A smiling photograph of a female subject (23 years of age) who fulfilled the criteria of soft tissue normative values and a balanced smile was obtained. The photograph was manipulated to simulate six lingual and labial inclinations at 5-degree increments to a maximum of 15 degrees. The seven photographs were randomly distributed in a binder to three groups of raters (20 dentists, 20 orthodontists and 20 laypeople) who scored the attractiveness of the photographic variations using a visual analogue scale (VAS). Comparisons of the mean scores were carried out by repeated analysis of variance, univariate tests and multiple Bonferroni comparisons. Results: The results showed a statistically significant interaction between the rater's profession and the aesthetic preference of incisor inclination. The profile smile corresponding to an increase in a labial direction had the highest score among all professions and among male and female raters. Conclusions: Orthodontists preferred the labial crown torque; dentists preferred the lingual crown torque; and laypeople appreciated the mild to moderate incisor inclination in both the lingual and the labial directions. The most preferred smile matched with a maxillary incisor inclined 98° to the horizontal line and +8° to the lower third of the face.

Smile characterization by U.S. white, U.S. Asian Indian, and Indian populations

With growing demand for high esthetic standards, dentists must understand patient perception and incorporate their preferences into treatment. However, little is known about how cultural and ethnic differences influence esthetic perception. The purpose of this study was to determine whether differences in ethnic background, including the possibility of assimilation, affected a layperson's perception of esthetic and smile characteristics. A survey was developed containing images that were digitally manipulated into a series of barely perceptible steps, changing 1 smile parameter to form a strip of images that displayed that parameter over a wide range. Data were collected with a customized program which randomly displayed a single image and allowed the subject to use the mouse to adjust an on-screen slider according to displayed instructions, that is, "Please move the slider to select the image you find to be most ideal"; or "Please move the slider to select the first image that you find unattractive." A convenience sample (n=288) comprised of U.S. whites, U.S. Asian Indians, and Indians living in India was surveyed. This sample provided a power of .86 to detect a difference of ±1.5 mm. Subjects evaluated images showing the smile arc, buccal corridor, gingival display, vertical overlap, lateral incisal step, maxillary midline to midface, and maxillary to mandibular midline. Rater reliability was assessed with the Fleiss-Cohen weighted Kappa (Kw) statistic and corresponding 95% confidence interval after each question was repeated in a random sequence. Choice differences due to ethnicity were assessed with a multiple randomization test and the adjusted P value with the step-down Bonferrroni method of Holm (α=.05). The Kw for the 17 variables in all 3 groups ranged from 0.11 for ideal vertical overlap to 0.64 for ideal buccal corridor space. Overall reliability was fair to moderate. Differences attributed to ethnicity were demonstrated between the Asian Indians and U.S. whites. Differences attributed to assimilation were demonstrated between U.S. Asian Indians and Asian Indians. Differences between U.S. Asian Indians and U.S. whites can be instructive and demonstrate the relative power of ethnicity and assimilation. A difference between these groups shows the power of ethnicity and no difference between these groups shows the power of assimilation. The ratings of the Asian Indians and the U.S. whites showed a clinically significant difference for Ideal Buccal Corridor and Maximum Smile Arc. There were no significant differences between the U.S. Asian Indians and Asian Indians. There were clinically significant differences between the U.S. Asian Indians and U.S. whites only for Ideal Buccal Corridor. Ethnicity had a significant effect on the esthetic choices for Buccal Corridor and Smile Arc. There is no conclusive evidence for assimilation.

Smile esthetics from the layperson’s perspective

Computer-based smile esthetic surveys based on slider technology allow more precise control of variables and the possibility of obtaining continuous data. Variations in the perception of smiles from different facial perspectives have not been resolved. The objective of this study was to quantify the ideal and the range of acceptable values for smile variables judged by laypersons from a full-face perspective for comparison with lower-face data. Mirrored and symmetric male and female full faces previously determined by peers to be of average attractiveness were used. Ninety-six laypersons judged these smile variables: smile arc, buccal corridor fill, maxillary gingival display, maxillary midline to face, maxillary to mandibular midline discrepancy, overbite, central incisor gingival margin discrepancy, maxillary anterior gingival height discrepancy, incisal edge discrepancy, and cant. The judges manipulated the variables using adjustable image technology that allowed the variable to morph and appear continuous on a computer monitor. Medians for each smile variable were compiled, and the Fleiss-Cohen weighted kappa statistic was calculated to measure reliability. Multiple randomization tests with adjusted P values were used to compare these data with those for lower-face views. Reliability ranged from 0.25 for ideal overbite to 0.60 for upper midline to face, except for upper and lower buccal corridor limits, which each had a kappa value near 0. There were no statistically significant differences between the ratings of male and female raters. The following variables showed statistically and clinically significant differences (>1 mm) when compared with the lower-face view: ideal smile arc, ideal buccal corridor, maximum gingival display, upper to lower midline, and occlusal cant. Although the smile arc values differed because of model lip curvature variations, the principle of tracking the curve of the lower lip was confirmed. For the full-face view, the raters preferred less maximum gingival display, less buccal corridor, more upper to lower midline discrepancy, and less cant of the occlusal plane. Reliability was fair to moderate with the exception of the buccal corridor limits. Most variables showed no clinically meaningful differences from the lower-face view. The acceptable range was quite large for most variables. Detailed knowledge of the ideal values of the various variables is important and can be incorporated into orthodontic treatment to produce an optimal esthetic smile.

Grounding the meaning of non-prototypical smiles on motor behavior

AbstractWe address how the motor system can contribute to the “meaning” component of smile perception. A smile perceiver can ground the meaning of non-prototypical smiles by interacting with the presenter to maintain the presenter's type of smile. In this case, the meaning of that smile is congruent with the motor behavior that elicits that smile (such as a funny gesture).

Influence of anterior tooth alignment on peer perception in 8- to 10-year-old children

The purpose of this research was to investigate whether anterior dental alignment in 8- to 10-year-old children influences the first impressions of their peers, and to verify the validity of the tested method. From colour photographs of two attractive children, one male and one female, Adobe Photoshop 5.0 was used to alter the images and create three versions of each photograph: one with good anterior dental alignment (OK smile), a second with proclination of the upper incisors (P-type smile), and finally one with moderate-to-severe anterior crowding (C-type smile). The six different photographs were shown to 121 subjects with mean age of 9.2 years (65 females and 56 males). Each subject was asked to view one photograph and subsequently respond to a questionnaire, the 'Smile perception questionnaire for children between the ages of 8 and 10' (SPQ 8-10), composed of 13 questions with graded responses. The responses for each photograph were analysed using linear regression analysis to determine the questionnaires validity as a whole and to investigate five area of common interest (honesty, intelligence, personal happiness, pleasantness, and extroversion). The results demonstrated that the questionnaire was reliable both from an internal coherence standpoint and from a test-retest reliability perspective. Data regarding the five areas of interest showed that 8- to 10-year-olds viewed their peers with well-aligned teeth more favourably as far as honesty, personal happiness, and intelligence were concerned. However, there was no statistically significant difference with regard to pleasantness and extroversion in children with harmonious, as opposed to crowded or proclined anterior teeth.

Mona Lisa’s Smile—Perception or Deception?

What gives Mona Lisa s smile such a mysterious quality? Livingstone (2000) has suggested that the portrait changes its expression depending on where on the portrait the observer looks. The mouth, which is the essential feature of Mona Lisa s remarkable expression (Kontsevich & Tyler, 2004), appears to form an enigmatic smile. Due to sfumato technique (Gombrich, 2005), this impression of a smile is more prominent in the gradual luminance changes that observers perceive mainly in the periphery of their vision— that is, in low spatial-frequency ranges. It is less prominent in the fine details that observers perceive only at the center of their gaze, in high spatial-frequency ranges. Consequently, the subtle smile one perceives while looking at Mona Lisa s eyes (when her mouth appears blurred) vanishes when one attempts to verify this impression by looking at the mouth with maximum visual acuity. Hence, the proposed basis for the elusive quality of Mona Lisa s smile is that ‘‘you can t catch her smile by looking at her mouth. She smiles until you look at her mouth’’ (Livingstone, 2000, p. 1299). In this study, we simulated the phenomenon for the first time experimentally via a saccade-contingent display-change technique that allowed us to subliminally alter the expression of faces depending on the beholder s gaze position.

Impact of dental asymmetries on the perception of smile esthetics

The purpose of this study was to evaluate the impact of anterior tooth asymmetries on the perception of smile esthetics. Three pleasant female smiles were digitally altered to simulate several degrees of asymmetry of the gingival margin of a maxillary central incisor, wear of a maxillary canine cusp, and a dental midline shift. Three groups of 50 raters--laypersons, orthodontists, and prosthodontists--evaluated the original and the altered images and used a visual analog scale to score smile esthetics. The threshold of the orthodontists and the prosthodontists for asymmetry of the gingival margin of a maxillary central incisor was 0.5 mm; the threshold for laypersons, who were less perceptive, was 2.0 mm. Wear of a maxillary canine cusp had no esthetic impact for any group of raters. Midline shifts became perceptible when equal to or greater than 1.0 mm for orthodontists and 3.0 mm for prosthodontists; laypersons saw no alteration. Laypersons, orthodontists, and prosthodontists have different perceptions of attractiveness when evaluating gingival margin height of a maxillary central incisor and a dental midline shift. These findings might help dental specialists to consider the patient's esthetic expectations when planning treatment.

Brief report: perception of genuine and posed smiles by individuals with autism.

Individuals with autism are impaired in the recognition of fear, which may be due to their reduced tendency to look at the eyes. Here we investigated another potential perceptual and social consequence of reduced eye fixation. The eye region of the face is critical for identifying genuine, or sincere, smiles. We therefore investigated this ability in adults with autism. We used eye-tracking to measure gaze behaviour to faces displaying posed and genuine smiles. Adults with autism were impaired on the posed/genuine smile task and looked at the eyes significantly less than did controls. Also, within the autism group, task performance correlated with social interaction ability. We conclude that reduced eye contact in autism leads to reduced ability to discriminate genuine from posed smiles with downstream effects on social interaction.

Convergence of receptive and expressive emotional communication in the human amygdala: an fMRI-study of pleasant facial emotion

Introduction: Facial expressions play an important role in the coordination of everyday social behaviour. Social interaction thereby depends on a person's ability both to send and receive emotional signals which can be selectively impaired for distinct emotions as we have previously shown for asymptomatic Huntington's gene carriers and deep brain stimulated Parkinsons's disease patients [1, 2]. The amygdala has emerged as a key structure in receptive processing of mainly negative emotions. However, its role in both, appraisal and expression of positive facial emotion remains unclear. We hypothesized that activation of the amygdala occurs both during perception and execution of smiles.

Perception of Genuine and Masking Smiles in Children and Adults: Sensitivity to Traces of Anger

The authors examined children's and adults' sensitivity to traces of anger in masking smiles by presenting participants with short video excerpts of smiles that differed by the intensity of an anger component. Fifty-two children, aged 6 to 12 years, and 26 adults were asked to judge whether a stimulus person was really happy or pretending to be happy. Six- and 7-year-old children were found to be sensitive to traces of anger, but less so than older children and adults. Researchers found evidence of explicit knowledge of the emotion hidden in masking smiles only in adult participants.

The perception of smiles

Os made magnitude estimates of the smiles on photographs of faces exposed for various durations. Very brief exposures (.02 sec) resulted in discriminability of smiles equivalent to that obtained with unlimited exposure. Repeated presentation of a face did not alter the magnitude estimates, and the high level of discriminability under brief exposures occurred even when recognition of the faces (old-new) was poor. Perception of a smile appears to occur extremely rapidly, perhaps as a wholistic process.