Bilateral asymmetry index
Mean distance between each landmark and the mirror image of its bilateral partner across the facial midline, as a percentage of interpupillary distance.
How to read it
the face is highly bilaterally symmetric at the resolution of the landmark detector.
a typical degree of bilateral asymmetry. Every face is asymmetric; the noise floor shown is how much of this value the detector itself contributes.
above-typical bilateral asymmetry at this resolution. Before reading anything into it: head yaw of even a few degrees inflates this value more than most real asymmetry does. Lee et al. (2025), with 400 raters, found no significant relationship between symmetry and attractiveness once averageness was controlled.
A symmetry score from a photo mostly measures landmark jitter plus head yaw. It is included because people ask for it, and reported with its noise floor so it cannot be over-read.
Reference values by population
| Reference population | Female (mean ± SD) | Male (mean ± SD) | n | Source |
|---|---|---|---|---|
| North American White | 3.2 ± 1.2 | 3.2 ± 1.2 | — | Typical range for healthy adults measured with 2D landmarks incl. detector noise. Provisional; not a population anthropometric value. prov. |
| East Asian | 3.2 ± 1.2 | 3.2 ± 1.2 | — | Typical range for healthy adults measured with 2D landmarks incl. detector noise. Provisional; not a population anthropometric value. prov. |
| South Asian | 3.2 ± 1.2 | 3.2 ± 1.2 | — | Typical range for healthy adults measured with 2D landmarks incl. detector noise. Provisional; not a population anthropometric value. prov. |
| African / African diaspora | 3.2 ± 1.2 | 3.2 ± 1.2 | — | Typical range for healthy adults measured with 2D landmarks incl. detector noise. Provisional; not a population anthropometric value. prov. |
| Middle Eastern | 3.2 ± 1.2 | 3.2 ± 1.2 | — | Typical range for healthy adults measured with 2D landmarks incl. detector noise. Provisional; not a population anthropometric value. prov. |
| Hispanic / Latino | 3.2 ± 1.2 | 3.2 ± 1.2 | — | Typical range for healthy adults measured with 2D landmarks incl. detector noise. Provisional; not a population anthropometric value. prov. |
| Not specified — show pooled | 3.2 ± 1.2 | 3.2 ± 1.2 | — | Typical range for healthy adults measured with 2D landmarks incl. detector noise. Provisional; not a population anthropometric value. prov. |
Where these numbers come from
Transcribed from the cited anthropometric literature; SDs of ratios are propagated conservatively (independence assumed). Entries marked prov. await line-by-line audit against the primary tables — see the norm provenance note.
Why every value has an error bar
Every value Canthion reports carries a 1σ uncertainty propagated from MediaPipe Face Mesh's published accuracy (3.96% of inter-ocular distance mean absolute error per landmark, Kartynnik 2019). For a typical 300 px inter-pupil photo that is ≈12 px per landmark, which is why small ratios and angles get wide intervals. A number without an interval is a number pretending to be more precise than it is.
References
- Lee, Li, Rafiee, Jones & Shiramizu (2025). Further evidence that averageness and femininity, rather than symmetry and masculinity, predict facial attractiveness judgments. Sci Rep 15:5498. doi.org/10.1038/s41598-025-86974-0
- Kartynnik, Ablavatski, Grishchenko & Grundmann (2019). Real-time Facial Surface Geometry from Monocular Video on Mobile GPUs. arXiv:1907.06724. arxiv.org/abs/1907.06724
Related: how bone-level measurements are taken from a photo · methodology · all insights