I'm still on the fence. Years ago I rented a room in my house to an immigrant from South Korea who got his work visa (and later his green card) because he could sex chickens and the local farmers couldn't get anybody local who knew how to do it. He got great pay, and relatively easy work hours since as the taskers became tired, their error rate went up. He worked with several other sexers who were all either from South Korea or Japan.
He could never quite explain how he did it, but he did teach a few Americans at the poultry plant how to do it via the technique described in the article before moving on to some different trades.
I think another factor is almost certainly sound. The study I just cited dealt with photographs, but the plane watchers in the story would also have been able to hear the sounds of the planes. There are certain models of aircraft I can identify by the sounds of their engines alone because I have been around (or in) them so much. However, to most people they just sound like "jet noise" or "prop noise." Even though I can tell the difference, I would have a hard time explaining it because the vocabulary we have for describing sounds is not nearly as complete as the vocabulary we have for describing images (or at least my vocabulary is that way).
1: http://cognitrn.psych.indiana.edu/rgoldsto/courses/concepts/...
I believe the operator really doesn't know how he parses the information, and at these speed and error rates it must be something more than seeing bumps or not.
Could it be that this method would not be efficient, economical?
I remember an anecdotal story of how, in the old days, the great players of chess could tell you if the move just made was good or not but could not explain why. They somehow just knew.
The mystery was that no one could explain exactly how it was done. It was somehow based on very subtle visual cues, but the professional sexers could not say what those cues were. They would look at the chick’s rear (where the vent is) and simply seem to know the correct bin to throw it in.
And this is how the professionals taught the student sexers. The master would stand over the apprentice and watch. The student would pick up a chick, examine its rear, and toss it into one bin or the other. The master would give feedback: yes or no. After weeks on end of this activity, the student’s brain was trained to a masterful—albeit unconscious—level.
Huh? "Subtle visual cues" that seemingly cannot be described, but can somehow be taught and passed on? I call bs.
Just googled it, here's the technique:
Vent sexing, also known simply as venting, involves literally squeezing the feces out of the chick, which opens up the chick's anal vent (called a cloaca) slightly, allowing the chicken sexer to see if the chick has a small "bump", which would indicate that the chick is a male. Some females have very small bumps, but rarely do they have the large bumps male chicks possess.