Il problema che viene sollevato nel precedente post Effetto stroop e freccia è capire quando la linea comincia a indicare in quale dei due versi viene seguita.
Ho provato a proporre la questione a John Ptak, che ne sa molto. Mi ha risposto (spero non si arrabbierà se lo cito) :
«The index finger as part of an entire hand is seen often, especially in early works (through the Renaissance and into the Baroque) but I must say that I’ve not seen the arrow sign used in its place early, even in the 19th century. When looking at annotated works in the 19th century and earlier it’s mostly lines or dots or dashes and even the drawn finger/hand, but not arrows. Good question! I don’t have an answer, but I suspect that the use of the arrow is very (100-150 years?) recent».
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Sinsemia 
