Thumb's rule tested: visual angle of thumb's width is about 2 deg.
Measures of the size of various hand parts and their viewing distance when held at arm's length were made on one hundred and eighteen undergraduate students. A simple rule of thumb can be confirmed: Visual angle of the width of the thumb held at arm's length is about 2 deg. The thumbnail subtends about 1.5 deg and the index fingernail about 1 deg in width, when both are held at arm's length. These figures are good approximations for males and females, although a significant, direct, linear relationship exists between hand-part size and the visual angle of the part at arm's length.
O'Shea
R P
RP
Department of Psychology, University of Otago, Dunedin, New Zealand.
D000328:Adult; D000886:Anthropometry; D004215:Distance Perception / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009949:Orientation / Q000502:physiology*; D011601:Psychophysics; D012858:Size Perception / Q000502:physiology*; D013933:Thumb / Q000033:anatomy & histology*