Hands

Hand morphology: hand size, palm shape, finger length proportions (digit ratio 2D:4D), finger morphology, nail morphology, knuckle prominence. The 2D:4D digit ratio is the most-cited individual hand-anthropometry dimension; Manning's prenatal-androgen-exposure hypothesis remains debated but the ratio itself is a well-established measurement with population-level variation.

Dimensions

• Hand size (relative to body)

  partly photo-observable

  ordinal · hand_size_qualitative

  Hand length relative to body height, captured qualitatively.

  Aligned with anthropometric descriptors of hand-length proportional to height (typical ratio ~10.4-11.0%).

  Valid values (3)

  • smallSmall
  • averageAverage
  • largeLarge

• Palm shape

  photo-observable

  categorical · palm_shape_qualitative

  Shape of the palm in proportional terms.

  Aligned with descriptors used in chiromancy-adjacent hand-anthropometry literature.

  Valid values (3)

  • squareSquare— Palm length approximately equal to palm width.
  • rectangular_longRectangular / long— Palm length substantially exceeds width.
  • wide_shortWide / short— Palm width approaches or exceeds length.

• 2D:4D digit ratio

  partly photo-observable

  categorical · manning_2D_4D

  Ratio of index-finger length (2D) to ring-finger length (4D). Sex-dimorphic on average (males ~0.95-0.98, females ~0.97-1.00) with substantial individual variation.

  Manning JT, Scutt D, Wilson J, Lewis-Jones DI (1998). The ratio of 2nd to 4th digit length: a predictor of sperm numbers and concentrations of testosterone, luteinizing hormone and oestrogen. Human Reproduction, 13(11): 3000-3004.

  Valid values (3)

  • low_4D_dominantLow (ring finger longer)— 2D:4D ratio < ~0.95; ring finger clearly longer than index. More common in males.
  • balancedBalanced— 2D:4D ratio ~0.95-1.00; subtle or no length difference.
  • high_2D_dominantHigh (index finger longer)— 2D:4D ratio > ~1.00; index finger clearly longer than ring. Less common; more common in females.

• Finger morphology

  photo-observable

  categorical · finger_thickness_qualitative

  Overall thickness and shape of the fingers.

  Aligned with hand-anthropometry descriptors used in glove-fitting and ergonomics literature.

  Valid values (5)

  • slenderSlender— Long, thin fingers; narrow fingertips.
  • balancedBalanced— Average finger thickness.
  • thickThick— Substantial finger girth.
  • taperedTapered— Wider at the base, narrower at the tips.
  • spatulateSpatulate— Widening at the fingertips.

• Knuckle prominence

  photo-observable

  ordinal · knuckle_prominence_qualitative

  Visibility of the metacarpophalangeal joints as surface landmarks.

  Aligned with surface-anatomy descriptors of metacarpophalangeal-joint visibility.

  Valid values (3)

  • subtleSubtle— Knuckles barely visible; soft-tissue coverage smooth.
  • moderateModerate
  • prominentProminent— Clear knuckle landmarks even at rest.

• Nail shape (when ungroomed)

  photo-observable

  categorical · nail_shape_qualitative

  Native fingernail shape when not artificially shaped.

  Aligned with descriptors used in dermatology and manicure literature.

  Valid values (7)

  • squareSquare
  • roundRound
  • ovalOval
  • almondAlmond
  • stilettoStiletto / pointed— Often artificial; native nails rarely take this shape.
  • groomed_artificialGroomed / artificial— Visible manicure or artificial nails; native shape not assessable.
  • not_visibleNot visible

• Wrist breadth (relative)

  partly photo-observable

  ordinal · wrist_breadth_qualitative

  Wrist circumference relative to body proportions. Different from but related to body-shape.json's frame_size_estimate.

  Aligned with frame-size literature; wrist circumference is the standard Frisancho frame-size proxy.

  Valid values (3)

  • narrowNarrow
  • averageAverage
  • wideWide