10 things that can change a parent-child face comparison

A parent-child resemblance test compares images taken from people at very different stages of facial development. These ten factors can influence what the model sees and how the result should be interpreted.

1. The child's age

A baby's facial proportions differ substantially from those of an older child. The face continues to develop, so resemblance visible at one age may appear differently later.

2. The parent's age in the chosen photo

Comparing a current child photo with a current adult portrait is different from comparing the child with a photo of the parent at a similar childhood age. Neither approach proves anything biologically; they simply present different visual conditions.

3. Head angle

Strongly different angles can make facial proportions appear less comparable. Near-frontal photos usually provide a more balanced view of both sides of the face.

4. Lighting

Uneven light can hide contours around the eyes, cheeks and jaw. Similar, soft lighting generally makes visual comparison easier.

5. Expression

Smiles and exaggerated expressions change the geometry of the mouth, cheeks and eyes. Neutral or mild expressions often reduce this source of variation.

6. Camera distance

A close selfie and a portrait taken from farther away can have noticeably different perspective. Central facial features may appear larger in close images.

7. Image resolution

Blur, compression and tiny faces reduce visible detail. A model cannot recover information that is not present in the image.

8. Filters and editing

Beauty filters may reshape facial features. If one family member's photo is edited and another is natural, the comparison includes those editing differences.

9. Natural family variation

A child can inherit visible traits from both sides of the family. Eyes may remind people of one parent while face shape or smile resembles the other.

10. The scoring mode

Different scoring modes can map the same underlying comparison differently. A stricter mode may display a more conservative percentage than a normal mode.