would go for that def. ,, no farmer has yet bought a chicken that lays more eggs than others , by handling or looks , or no farmer can buy a cow that can have more milk than another by looks [was going to say or by handling ;D] they come n all shapes and sizes and looks,, if anything i would go more by there actions , vibrant , bouncy , bright , but even that is just a guess ,, sometimes i think you can get a hunch , through experience, again this is not fool proof , by the proer management ,the good bird will show itself, by results