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"Scientific findings have reinforced the thoughts of Atherton and those before him, shoring up the empirical theories resulting from nearly five centuries of careful observations by the best original thinkers in fly fishing. In addition to investigating the visual acuity of trout, scientists have also studied the ability of the fish to respond to various traits of the food item. It is eminently clear from these technical experiments, as well as observations made by fly fishers, that the four characteristics which most strongly represent the essence of life, and therefore trigger the trout's feeding response, are size, shape, color, and behavior. Trout respond to these four traits of the food item whether feeding opportunistically or selectively."