Dear Mr. Moreland,
With respect to your query, although all of the explanations forwarded
so far are definitely correct, I do believe that the source of the
problem is something else, and under certain limited conditions can be
debilitating for the very "theoretical" reasons you originally cited.
The reason is that prolonged fixation creates a "long-lasting" image on
the retina, the after effect, which can be visited by closing the eye or
fixating a dark background. The longer the fixation, the stronger the
image, and due to continuous micro movements of the eye, the unsharper
its boundaries.
Under steady lighting conditions, however, this basically weaker,
imprinted-on-the-retina image never competes with the brighter actual
image of the target. But were background lighting conditions to change,
becoming dimmer, the unsharp imprinted image could come to the fore,
regardless of the actual locus of fixation, and thus possibly compete
with the true image. I have in fact often tested it; it is nonsense, and
certainly NOT the reasons for adopting short fixation times.
I have compared 10 shots made with short fixation times, with 10 made
after fixations of 10-15 sec., with no appreciable difference in
accuracy.
Another reason, taught by Japanese masters of archery, is that every
aspect of the shooting act (taking stance, lifting the bow, pulling and
holding the straining taut bow, and finally releasing the arrow) must
find the entire body in a super-relaxed condition.
Our eyes rarely fixate any source unflinchingly for long. It is
unnatural to do so, and will lead to stress, which may increase the
frequency of the normal micro-saccades to avoid the fatigue, and this
last, could possibly account for the ensuing inaccuracy.
Sincerely, S. Rasmjou