If sensory biases led animals to choose lower-fitness animals over higher-fitness animals, I suspect that the biases would be eliminated rather quickly. It seems unlikely that an ornament could persist as a pure sensory bias effect that does not convey any fitness information. That grants too much evolutionary power to males evolving ornaments and not enough to females evolving sensory discrimination abilities. Animals choosing mates do not want their senses subverted by meaningless ornaments. They may like fitness indicators that have a lot of sensory appeal, but they should not be favoring sensory appeal over fitness information.
Often there may be no conflict between sensory bias theory and fitness indicator theory. They are complementary perspectives on sexual selection. Sensory bias theory reminds us that mate choice is mediated by perceptual abilities, and that as new perceptual abilities evolve, the way is opened for new kinds of sexual ornaments to evolve. With the evolution of eyes came the possibility of visual ornaments. With the evolution of bird ears came the possibility of bird song. And perhaps, with the evolution of language comprehension abilities in our ancestors, came the possibility of sexual selection for much more complicated thoughts and feelings expressed through language.
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