Facial symmetry
Encyclopedia
Facial symmetry, is one element of bodily symmetry, including fluctuating asymmetry
. Along with traits such as averageness
and youthfulness it influences judgements of aesthetic traits of physical attractiveness
and beauty
, and is associated with fitness-linked traits including health
, It is also hypothesized as a factor in both interpersonal attraction
and interpersonal chemistry.
, and not deliberate asymmetrical structures found in some animals, develops throughout the lifespan of the individual and is a sign of the phenotype
being subjected to some levels of stress.
Biologists, based on work with animals mostly, are exploring new links between facial symmetry and physical attractiveness
. When a face is symmetrical vertically, so that left and right sides mirror each other along a vertical axis, the mirroring makes it easy cognitively
and perceptively
for a human mind to tell if the two sides match. There is a visual copy of each side in plain view making it easy for a person to judge if left matches right. The mind can make this mental comparison in a split second to look for aberrations, distortions, or lopsided features. If faces were not symmetrical, then the mind would have a more challenging cognitive task of comparing the seen face with a remembered standard face. The split-second analysis of symmetry is a reproductive advantage, particularly for males, since a male can decide quickly who are the most beautiful females and court them first and spend more time with them. An additional benefit to symmetry is because it takes less information storage since one strand does double duty; in effect, less DNA is needed to make more of a human being and brings the benefit of shorter DNA strands and biological efficiency. Overall, symmetry is a rather difficult challenge to achieve biologically since the body has to coordinate a perfect match for each side when literally billions of cells are reproducing over years. Cell growth must happen in exactly the right order and speed so that left and right sides match exactly. If the left side rushes ahead even slightly faster than the right side, distortion can result. Inner structures must be built first, followed by intermediate and later tertiary structures such as the skin. Any weird biological experiences -- a wound, disease, malnutrition, a mutation -- can throw off this sequence on one side. When symmetry is achieved successfully despite numerous challenges, it is a visible signal of genetic health and is attractive physically.
The ability to cope with these pressures is partly reflected in the levels of symmetry. A higher degree of symmetry indicates a better coping system for environmental factors. While the visible signs of this may not be particularly apparent, it is thought that they have at least an unconscious
effect on people's perception of their beauty. Zaidel et al. in an empirical study upholds the claim that facial symmetry may be critical for the appearance of health. Their study disputes, however, the beauty or attractiveness claim.
Experimentally, when the shape of facial features is varied (with skin textures held constant), increasing symmetry of face shape increases ratings of attractiveness for both male and female faces . These findings imply facial symmetry may have a positive impact on mate selection in humans.
Non-scientific theories of attraction and symmetry abound. For instance the conjunction "of similar and related parts that are to some extent contrasted to one another" has been considered to have the most aesthetic appeal. Likewise shared features echoism
, proportions and similarity to people the person bonded to early in life (prima copulism) have been suggested as relevant.
b- Hyperplasia of masseter muscle in clenching habit.
c- Patients using only one side in chewing
Fluctuating asymmetry
Fluctuating asymmetry is an organism’s deviation from bilateral symmetry. It can be measured in the body—as in bilateral symmetry of finger lengths—or in a particular organ...
. Along with traits such as averageness
Averageness
In attractiveness studies, averageness is one of the characteristics of physical beauty in which the average phenotype, i.e. outward appearance, of the individual theoretically characterizes averaged genotypes, thus indicating health and fertility. The majority of averageness studies and theories...
and youthfulness it influences judgements of aesthetic traits of physical attractiveness
Physical attractiveness
Physical attractiveness refers to a person's physical traits which are perceived to be aesthetically pleasing or beautiful. The term often implies sexual attractiveness or desirability, but can also be distinct from the two; for example, humans may regard the young as attractive for various...
and beauty
Beauty
Beauty is a characteristic of a person, animal, place, object, or idea that provides a perceptual experience of pleasure, meaning, or satisfaction. Beauty is studied as part of aesthetics, sociology, social psychology, and culture...
, and is associated with fitness-linked traits including health
Health
Health is the level of functional or metabolic efficiency of a living being. In humans, it is the general condition of a person's mind, body and spirit, usually meaning to be free from illness, injury or pain...
, It is also hypothesized as a factor in both interpersonal attraction
Interpersonal attraction
Interpersonal attraction is the attraction between people which leads to friendships and romantic relationships. Interpersonal attraction, the process, is distinct from perceptions of physical attractiveness which involves views of what is and is not considered beautiful or attractive.The study of...
and interpersonal chemistry.
Health and physical attractiveness
Edler cited research supporting the claim that bilateral symmetry is an important indicator of freedom from disease, and worthiness for mating. Random differences between the two sides, known in biological terms as Fluctuating asymmetryFluctuating asymmetry
Fluctuating asymmetry is an organism’s deviation from bilateral symmetry. It can be measured in the body—as in bilateral symmetry of finger lengths—or in a particular organ...
, and not deliberate asymmetrical structures found in some animals, develops throughout the lifespan of the individual and is a sign of the phenotype
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
being subjected to some levels of stress.
Biologists, based on work with animals mostly, are exploring new links between facial symmetry and physical attractiveness
Physical attractiveness
Physical attractiveness refers to a person's physical traits which are perceived to be aesthetically pleasing or beautiful. The term often implies sexual attractiveness or desirability, but can also be distinct from the two; for example, humans may regard the young as attractive for various...
. When a face is symmetrical vertically, so that left and right sides mirror each other along a vertical axis, the mirroring makes it easy cognitively
Cognition
In science, cognition refers to mental processes. These processes include attention, remembering, producing and understanding language, solving problems, and making decisions. Cognition is studied in various disciplines such as psychology, philosophy, linguistics, and computer science...
and perceptively
Perception
Perception is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information. All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs...
for a human mind to tell if the two sides match. There is a visual copy of each side in plain view making it easy for a person to judge if left matches right. The mind can make this mental comparison in a split second to look for aberrations, distortions, or lopsided features. If faces were not symmetrical, then the mind would have a more challenging cognitive task of comparing the seen face with a remembered standard face. The split-second analysis of symmetry is a reproductive advantage, particularly for males, since a male can decide quickly who are the most beautiful females and court them first and spend more time with them. An additional benefit to symmetry is because it takes less information storage since one strand does double duty; in effect, less DNA is needed to make more of a human being and brings the benefit of shorter DNA strands and biological efficiency. Overall, symmetry is a rather difficult challenge to achieve biologically since the body has to coordinate a perfect match for each side when literally billions of cells are reproducing over years. Cell growth must happen in exactly the right order and speed so that left and right sides match exactly. If the left side rushes ahead even slightly faster than the right side, distortion can result. Inner structures must be built first, followed by intermediate and later tertiary structures such as the skin. Any weird biological experiences -- a wound, disease, malnutrition, a mutation -- can throw off this sequence on one side. When symmetry is achieved successfully despite numerous challenges, it is a visible signal of genetic health and is attractive physically.
The ability to cope with these pressures is partly reflected in the levels of symmetry. A higher degree of symmetry indicates a better coping system for environmental factors. While the visible signs of this may not be particularly apparent, it is thought that they have at least an unconscious
Unconscious
Unconscious might refer to:In physiology:* unconsciousness, the lack of consciousness or responsiveness to people and other environmental stimuliIn psychology:...
effect on people's perception of their beauty. Zaidel et al. in an empirical study upholds the claim that facial symmetry may be critical for the appearance of health. Their study disputes, however, the beauty or attractiveness claim.
Interpersonal attraction
A large body of work has been conducted relating symmetry to attractiveness, though this is not yet incorporated in this article. Symmetry may act as a marker of phenotypic and genetic quality and is preferred during mate selection in a variety of species .Experimentally, when the shape of facial features is varied (with skin textures held constant), increasing symmetry of face shape increases ratings of attractiveness for both male and female faces . These findings imply facial symmetry may have a positive impact on mate selection in humans.
Non-scientific theories of attraction and symmetry abound. For instance the conjunction "of similar and related parts that are to some extent contrasted to one another" has been considered to have the most aesthetic appeal. Likewise shared features echoism
Echoism
Echoism may refer to:*The formation of words by imitating sounds *A theorised aspect of facial symmetry...
, proportions and similarity to people the person bonded to early in life (prima copulism) have been suggested as relevant.
Congenital defect
- Facial hemi-trophy or hypertrophy of superfacial tissue , muscle & bone.
- Mandibular Condylar hypoplasia due to intrauterine or birth trauma.
- TMJ Ankylosis, the mandible moves to the affected side.
- Mandibular body or ramus hyperplasia, the mandible moves to the unaffected side.
Muscular
a- Atrophy of facial musculature following Bell's palsy.b- Hyperplasia of masseter muscle in clenching habit.
c- Patients using only one side in chewing
External links
- "Teeth, Beauty, Biology, and Health" – a class handout on dentition and facial symmetry at the College of Dentistry – University of Illinois at Chicago.
- "Chimeric Face Experiment" – Perform a facial symmetry and attractiveness experiment by uploading a photo
- FaceResearch – Online studies on facial symmetry by researchers affiliated with University of Aberdeen (Scotland) School of Psychology, and University of St. Andrews (Scotland).
- "A facial symmetry plugin for the GIMP" -- Try experimenting with facial symmetry, using open source software.