French artist Albert Sauteur suggested in 2014 that differences between the paintings were accounted for not only by the model having aged, but that the narrower face and closer eyes in the Louvre painting could be accounted for by Leonardo experimenting with painting from a binocular visual perspective, rather than the traditional monocular perspective. British fine arts consultant Archibald Cecil Chappelow of the Royal Society of Arts, wrote in 1956 that "the face is superbly painted, and the hands more neatly defined than those in the Louvre painting". Asmus specifically asserted that "portions of the hands in the Louvre painting have been criticized as being 'fat and ugly'", while "it is intriguing to note that the Isleworth thumb is more slender and closer to what would be expected from Leonardo".
The differences between the paintings were attributed not only to the model's aging, but also to Leonardo experimenting with a binocular visual perspective instead of the traditional monocular perspective.