The Role of Eyebrows in Face Recognition

Abstract

The face recognition process in psychology is a highly prospective and relevant topic since many technologies are attempting to emulate this natural human ability. An examination of the literature reveals that eyebrows play a major role in the face as well as in the emotion recognition processes alongside the eyes. These two facial features are considered fundamentals for the recognition of any human face, both familiar and unfamiliar. Although peripheral facial features have a role for unfamiliar faces, they are still superseded by eyebrows in terms of importance. Eyes and eyebrows are constants in a familiar face recognition process, but distinctive and deviant facial features can become the third determinant in significance as well. Both human face recognition and face recognition simulated by computer systems significantly rely on eyebrows to recognize faces successfully.

Introduction

It is important to note that the face recognition process is a complex set of psychological and cognitive responses. The given analysis will primarily focus on how eyebrows impact the rate and level of facial recognition in terms of being exposed to familiar faces, such as celebrities. Eyebrows play a significant role in facial recognition since they mediate the recognition through kinematics, emotion, and structural specificities, always remaining critical alongside the eyes.

Literature Review

Detailed Introduction to Past Research #1

Although the topic of face recognition is vast and expansive, there is a rather limited amount of literature with an emphasis on psychology within recent publication dates. The first study of interest primarily focuses on identifying key super-recognizers of the face recognition process in human cognition. The sample size consisted of 106 (n = 106) participants whose face-processing abilities were measured through the Cambridge Face Memory Test (CFMT) (Tardif et al., 2018). The researchers used popular celebrity faces as stimuli, where the identification was marked as true positive. The findings suggest that the “use of both eyes or eyebrows as well as the mouth was a statistically significant predictor of face-recognition ability” (Tardif et al., 2018, p. 5). It should be noted that both eyes and eyebrows were equally critical in face recognition processing, followed by mouth. This means that eyebrows play a significant role in facial recognition. Recognition of familiar faces, such as celebrities, significantly decreases when the eyebrows are removed.

Detailed Introduction to Past Research #2

The second research of interest is focused on emotional expression kinematics and recognition. The study is conducted on the basis of earlier findings on the role of the eye and eyebrows in expressing facial emotion (Sowden et al., 2021). In other words, a greater degree of emphasis is put on eyebrows and eyes during face recognition because their kinematics and movements are the primary means of communicating emotions through facial expressions. The authors of the publications conducted a series of four experiments with sample sizes between 27 and 67, depending on the setup (Sowden et al., 2021). The participants were asked to rate each face on the basis of their emotional perception when they were presented with a video. The findings suggest that there were “significant differences, whereas both eyebrow and mouth movements significantly differentiated posed emotions, this was not the case for spontaneous expressions, which could only be differentiated by eyebrow movements” (Sowden et al., 2021, p. 1047). In other words, for all facial expressions, only eyebrows were relevant in terms of kinematics, which explains why eyebrows play a significant role in face recognition.

Detailed Introduction to Past Research #3

The third study of interest focuses on facial expression recognition from the standpoint of a psychological perspective. Similar to the previous study, it bases its direction of research on previous literature, where an emphasis is made on the connection between facial recognition and emotional expression (Liliana et al., 2019). In order to test the best parameters for fuzzy emotion and face recognition framework, a wide range of facial features were identified in terms of their significance to successful recognition (Liliana et al., 2019). The fuzzy emotion inference system process diagram shows that the top priority parameters were eyebrows, such as left eyebrow, right eyebrow, and inner eyebrow.

Out of ten different facial feature parameters used on the framework, three were eyebrow-related, while only two were eye-related. Other factors were the inner mouth, outer mouth, inner lips, and nose (Liliana et al., 2019). Eyebrows were the most critical for face recognition, and they were essential for emotion recognition as well. Results indicate that the face “recognition result was correct if the system accurately captured the emotion which was crosschecked to the image label on the dataset and the expert rater validation” (Liliana et al., 2019, p. 400). Therefore, the interconnectedness between emotion processing and face recognition was substantiated by the findings. This means that eyebrows play a significant role in facial recognition.

Detailed Introduction to Past Research #4

The fourth study’s purpose was to analyze the face recognition of unfamiliar faces. The researchers wanted to understand how face recognition proceeds when a person is presented with a new and unfamiliar face. They recruited 60 participants (n = 60) and provided them with stimuli of faces, the peripheries of which were altered through masking, gapping, and mismatching (García-Zurdo et al., 2020). The ANOVA test was conducted to determine the accuracy rates and reaction times as well as true positive instances. The findings suggest that unfamiliar face-matching recognition can be impacted by peripheries, but the recognition is mainly mediated by eyes and eyebrows, followed by mouth (García-Zurdo et al., 2020). This goes alongside the first research study presented above, meaning both familiar and unfamiliar face recognition depend on eye and eyebrows, with a periphery being slightly more critical for the latter. It is stated that “eyebrows should also be considered an important internal feature, given their importance in identification” (García-Zurdo et al., 2020, p. 1768). In other words, eyebrows play a significant role in facial recognition.

Detailed Introduction to Past Research #5

The fifth study focuses on cognitive discriminant features in the face recognition process. It essentially tests the hypothesis that subjectively abnormal or deviant facial features are used to recognize familiar faces, such as having a big nose or noticeable mole. The researchers use the Gaussian kernel face recognition classifier system with the database to determine the degree of significance of discriminant features. It is stated: “Suppose a person whose eyes, eyebrows, nose are close to the average respective facial feature, but his/her mouth feature considerably deviates with respect to the deviations of other subject’s mouths” (Firouzian & Firouzian, 2020, p. 11). Under such conditions, “the mouth feature will be an appropriate discriminating feature for this subject” (Firouzian & Firouzian, 2020, p. 11). Therefore, face recognition is primarily mediated by eyes and eyebrows, but if there is an element of facial feature deviance by a substantial margin, then it will be used for recognition as well. However, the basis for face recognition remains the same in terms of fundamentals, which includes both eyes and eyebrows. Thus, eyebrows play a critical role in facial recognition.

General Literature Review

In order to comprehensively determine the significance and role of eyebrows in the face recognition process, it is essential to review the existing body of recent general literature on the subject. The recent COVID-19 pandemic and the extensive use of masks revitalized the research on the role of eyes and eyebrows in face recognition. A study found that “the highest accuracy results were 76.04% and 98.61% for the limited dataset and 96.88% and 93.22% for the larger dataset for the eye and eyebrow images, respectively” (Lionnie et al., 2022, p. 208). In other words, there is a greater level of accuracy in face recognition when eyebrows are the prime focus of interest compared to using the eyes themselves. This observation is substantiated by another research, where the findings suggest that eyebrows as “facial features are critical for familiar face recognition” (Abudarhama et al., 2019, p. 73). Thus, familiar faces tend to be better recognized through eyebrows compared to eyes.

Literature from plastic surgery research and facial beautification provides valuable insight on the topic as well. It is stated that the process of facial beautification greatly alters the face recognition rate, but if eyebrows remain similar before the change, then face recognition is minimally impacted (Rathgeb et al., 2019). The finding is an interesting and relevant one since it means that despite massive changes to the eyes, such as eyelid surgery, the retention of an eyebrow composition preserves the face recognition capabilities. Other researchers found that it is not only the eyebrow composition and structure that matters, but rather, it is a functional role in emotional messaging and accentuation of expressions of an individual (Hwang, 2021). Therefore, how a person uses his or her eyebrows, in addition to the structural specifics, is what makes eyebrow-mediated face recognition superior to the eye-mediated version.

Findings in the field of facial biometry provide an interesting insight into the role of eyebrows in facial recognition as well. As with the fuzzy emotion inference system process diagram mentioned above, a study on faces with smiles found a similar pattern. It identified 27 different facial distance parameters, among which the eyebrows were significant predictors of smiley face recognition’s true positive outcome (Taskirar et al., 2019). The most accurate identifications and measurements were made when eyes, eyebrows, and mouth were given the highest weight in the factorial analysis.

Limitations

It should be noted that the existing body of evidence on the significance of eyebrows in face recognition is large and substantive. However, some limitations can be identified, especially with respect to eye and eyebrow distinction. There seems to be a lack of specifically focused studies that comparatively examine the role of eye and eyebrows in face recognition by solely assessing these two facial features. The vast majority of studies focus on these two together, emphasizing that both are critical at being a top priority, which is followed by mouth or deviant factors. In addition, there seems to be a limitation when it comes to distinguishing between emotion recognition and face recognition, which is further complicated by familiarity or unfamiliarity with a particular face.

Potential Future Research Areas

By accounting for the identified sources of evidence as well as the minor limitations above, one can propose that potential future research areas should focus on eyes and eyebrows exclusively. They need to be comparatively examined in terms of significance, such as using images with either eyes or eyebrows removed. In addition, there needs to be research focused on examining the role of eyebrows in face recognition compared to emotion recognition since these two are difficult to distinguish.

Conclusion

In conclusion, eyebrows, alongside eyes, play a significant role in facial recognition because they mediate face recognition through kinematics, emotion, and structural specificities. It should be noted that both eyes and eyebrows are equally critical in face recognition processing, followed by the mouth. Only eyebrows are relevant for all facial expressions in terms of kinematics, which explains why eyebrows play a significant role in face recognition. In addition, eyebrows are the most critical for face recognition because they are vital for emotion recognition as well. Both familiar and unfamiliar face recognition depends on eye and eyebrows, with a periphery being slightly more critical for the latter. If there is a facial feature deviant by a substantial margin, then it will be used for recognition as well alongside the eyes and eyebrows. The ability to recognize faces is maintained by maintaining the composition of the eyebrows, even in the face of significant ocular modifications like eyelid surgery. Studies that compare the function of the eye and eyebrows in face identification by evaluating these two facial features alone, however, appear to be lacking.

References

Abudarhama, N., Shkillera, L., & Yovel, G. (2019). Critical features for face recognition. Cognition, 182, 73-83. Web.

Firouzian, I., & Firouzian, N. (2020). Face recognition by cognitive discriminant features. International Journal of Nonlinear Analysis and Applications, 11(1), 7-20. Web.

García-Zurdo, R., Frowd, C. D., & Manzanero, A. L. (2020). Effects of the facial periphery on unfamiliar face recognition. Current Psychology, 39, 1767–1773. Web.

Hwang, K. (2021). Eyebrows, facial expression, and ‘Poem to the Eyebrow (Blason du Sourcil).’ Journal of Craniofacial Surgery, 32(8), 784-787. Web.

Liliana, D. Y., Basaruddin, T., Widyanto, M. R., & Oriza, I. I. D. (2019). Fuzzy emotion: A natural approach to automatic facial expression recognition from a psychological perspective using a fuzzy system. Cognitive Processing, 20, 391-403. Web.

Lionnie, R., Apriono, C., & Gunawan, D. (2022). Eyes versus eyebrows: A comprehensive evaluation using the multiscale analysis and curvature-based combination methods in partial face recognition. Algorithms, 15(6), 208. Web.

Rathgeb, C., Dantcheva, & Busch, C. (2019). Impact and detection of facial beautification in face recognition: An overview. Journals & Magazines: IEEE Access, 7, 152667-152678. Web.

Sowden, S., Schuster, B. A., Keating, C. T., Fraser, D. S., & Cook, J. L. (2021). The role of movement kinematics in facial emotion expression production and recognition. American Psychological Association, 21(5), 1041-1061. Web.

Tardif, J., Duchesne, X. M., Cohan, S., Royer, J., Blais, C., Fiset, D., Duchaine, B., & Gosselin, F. (2018). Use of face information varies systematically from developmental prosopagnosics to super-recognizers. Psychological Science, 30(2), 1-9. Web.

Taskirar, M., Killioglu, M., Kahraman, N., & Erdem, C. E. (2019). Face recognition using dynamic features extracted from smile videos. IEEE International Symposium on Innovations in Intelligent Systems and Applications, 18869192, 1-6. Web.