The human mind is a strange and wonderful thing.  Not only can we learn to consciously perform complex tasks, but we can teach ourselves to perform seemingly impossible tasks without ever knowing the steps to do so.  Take the example of chicken sexers, as examined in the September 2011 edition of Discover Magazine:

When chicken hatchlings are born, large commercial hatcheries usually set about dividing them into males and females, and the practice of distinguishing gender is known as chick sexing. Sexing is necessary because the two genders receive different feeding programs: one for the females, which will eventually produce eggs, and another for the males, which are typically destined to be disposed of because of their uselessness in the commerce of producing eggs; only a few males are kept and fattened for meat. So the job of the chick sexer is to pick up each hatchling and quickly determine its sex in order to choose the correct bin to put it in. The problem is that the task is famously difficult: male and female chicks look exactly alike.

Well, almost exactly. The Japanese invented a method of sexing chicks known as vent sexing, by which experts could rapidly ascertain the sex of one-day-old hatchlings. Beginning in the 1930s, poultry breeders from around the world traveled to the Zen-Nippon Chick Sexing School in Japan to learn the technique.

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.


This seems very much akin to athletes being able to instinctively execute split second plays without completely understanding the mechanics of what they are accomplishing, only slightly more voodoo.  A similar technique was used during World War 2 by British plane spotters:

During World War II, under constant threat of bombings, the British had a great need to distinguish incoming aircraft quickly and accurately. Which aircraft were British planes coming home and which were German planes coming to bomb? Several airplane enthusiasts had proved to be excellent “spotters,” so the military eagerly employed their services. These spotters were so valuable that the government quickly tried to enlist more spotters—but they turned out to be rare and difficult to find. The government therefore tasked the spotters with training others.

It was a grim attempt. The spotters tried to explain their strategies but failed. No one got it, not even the spotters themselves. Like the chicken sexers, the spotters had little idea how they did what they did—they simply saw the right answer.

With a little ingenuity, the British finally figured out how to successfully train new spotters: by trial-and-error feedback. A novice would hazard a guess and an expert would say yes or no. Eventually the novices became, like their mentors, vessels of the mysterious, ineffable expertise.

The fact that our unconscious minds can learn how to perform tasks that our conscious minds have no ability to grasp is equal parts fascinating and creepy.

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6 Responses to “Sexing chickens”

  1. Lovely post. Now I want to try the technique put for myself.All I have to do is find some kind of zen master who will do the training with me.

  2. That’s incredibly interesting! I’d love to see studies using this as a teaching method for other complex tasks, I wonder just how far it can go?

    Goes to show, though, that despite having a fair grasp of how our brains are wired and how they function, we’ve only scratched the surface of what they are capable of.

  3. Although not a direct analogue, this pits me in mind of the mentats from Dune.

  4. I don’t know about plane spotting but when it comes to Chicken Sexing there was no mystery, no esoteric or intuitive gift. Just scientific discovery that required learning and practice like any skill. It is the same today see

    I have seen archive film from 1930s at Nagoya University, they dissected chicks and put the chick’s ‘parts’ under a microscope to confirm what they could see with their eyes under bright lights and the speed of distinguishing sex came with practice. The rest is Myth!

    Also see –

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