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Saturday, January 07, 2017

# Weird science news: Can chickens really do arithmetic?

Maybe, but they can't do calculus. Reason: they are chicken.

ll this week I've been struggling with bad science. First it was a 2010 paper in Science that has a flaw in their data analysis that changes their result from one thing to its opposite. That one paper has been cited over and over in my field. It has probably set back a cure for this particular disease by ten years.

So I wasn't in the most forgiving mood when I tried to relax this weekend and stumbled across an article titled “Number-space mapping in the newborn chick resembles humans' mental number line[1] where they claim that baby chickens can not only count, but they perceive integers as a sequence from left to right, just like humans.

It took a while to get the original paper, because sciencemag.org has either been hacked by the Russians or they've redesigned their website (which, really, amounts to the same thing). So at the moment every article is a 404. But there's a summary here; I got a copy a different way.

In an earlier paper Rugani et al. lined up 16 crackers from front to back, then trained the chicks to peck at the fourth cracker from the front. The row was then rotated and they found that the chickens now (mostly) pecked on the fourth cracker from the left. Conclusion: chickens put low numbers on the left, just like humans.

Heaven knows chickens can do chicken scratching. So maybe it's not so far-fetched to think three-day-old chickens can read and do arithmetic. But it's not clear why this is counting and not shape-matching. Then the authors did a follow-up experiment:

The authors write:

In our experiments, 3-day-old domestic chicks, once familiarized with a target number (5), spontaneously associated a smaller number (2) with the left space and a larger number (8) with the right space. The same number (8), though, was associated with the left space when the target number was 20. Similarly to humans, chicks associate smaller numbers with the left space and larger numbers with the right space.

To rephrase, baby chickens were trained to walk around a panel showing five squares to get to some food. Then they were presented with two identical panels with a certain number of black squares on them. If the number of squares was 2, the chickens walked around to the left. If the number was 8, they walked around it to the right. When they trained them with 20 squares, instead of walking around the right when shown a panel of 8, the chickens went left.

Before I switched to human diseases, I did animal learning experiments for decades. Animals, bless their little hearts, will do amazing things for food—we trained rats to swim in a little swimming pool, which they seem to enjoy, though not to the extent of putting up little umbrellas like us humans. The findings tell us something new about the brains of chickens, but we have no way of knowing whether the chickens see them as multiple objects or as a single composite object of different visual complexity.

The idea of a number line in chickens is highly implausible. It's like saying they read from left and right. Even all humans don't do that: as the authors admit, Semitic cultures read right to left, top to bottom. Chinese read top to bottom, right to left. I'm left-handed, and writing left to right has always felt unnatural to me, mainly because it smudges whatever I just wrote. Since there is evidence of visual lateralization in birds[2], which is induced by asymmetrical light stimulation during ontogeny, brain asymmetry in visual processing sounds like a better explanation for the chickens as well.

And now, if you'll excuse me, I've gotten hungry for crackers for some reason. But first I have to go around this obstacle which has, roughly, 20 things on it. For some odd reason I feel compelled to go counterclockwise.

1. Science. 2015 Jan 30;347(6221):534–536. doi: 10.1126/science.aaa1379. Number-space mapping in the newborn chick resembles humans' mental number line. Rugani R, Vallortigara G, Priftis K, Regolin L.

2. Front Psychol. 2014 Mar 25;5:206. doi: 10.3389/fpsyg.2014.00206. Functional and structural comparison of visual lateralization in birds - similar but still different. Manns M, Ströckens F.

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