Chicks count from left to right

02 February 2015

Interview with

Dr Hannah Rowland, University of Cambridge

Humans do it. Primates do it. And now it's been found out that birds can also do it:  3-day-old chickens have been shown to order numbers - low to high - from left to right - just like on a ruler! The findings, published in the journal Science, could indicate that this Counting chicknumerical ability is a feature of evolution, rather than culture - and could help explain why we pay more attention to things presented on our left... Zoologist Hannah Rowland from the University of Cambridge put Graihagh Jackson's numerical skills to the test...

Hannah - Plenty of people have been very interested in whether counting is a uniquely human behaviour. Lots of research has been done to figure out if animals have a sense of number. A really famous one that all students are taught is that peahens like to mate with peacocks that have about 150 eyes in their tail. If you take about 5 eyes out, the male peacock becomes far less attractive to the female. Now, people might think she is standing there going, "1,2,3,4..., 149, 150." But to actually tell the difference between a tail that has a 150 eyespots and 145, she doesn't have to count. So, she can pay attention to the asymmetry of the tail, or the density of spots in their tail. And so, while it might look like she's counting, she doesn't have to actually count at all.

Graihagh - Is there any way that you can tell if an animal can count because I imagine it's quite hard to disentangle what you're talking about and also, the whole, 1, 2, 3, 4, 5, 6, 7, 8?

Hannah - So, to actually test whether animals can count, you have to look for whether they can pay attention to the order of numbers or dots, or symbols. And there's lots of research been done on this with primates.

Graihagh - What about birds?

Hannah - Birds can certainly tell the difference between patches that have a lot of items or fewer items, but that's not counting as such. That's more numerical discrimination.

Graihagh - Given that the paper looked at domestic chickens, we thought it only appropriate to go and see some chickens ourselves. The only problem was, they were very scared of us. So, we had to feed them a bit of my pack lunch to get them to say hello.


"Now, look they're eating the peas."

Graihagh - So, my lunch didn't go to waste then. What are these guys called? Are they named after the colours because they're beautiful colours? You've got a grey one and sort of very warm orange then a light orange and a black with flex of teal almost.

Hannah - So, the black one is called Brumble and the grey is called Teazel and the yellowy and the brown ones are Heather and Bracken. Yeah, it's after their colours.

Graihagh - Let's talk a bit about this paper. What about the idea that if they can count, there is a tendency to count from left to right, just like humans do?

Hannah - So, this paper that's come out in science, it's based upon research that actually was right back in the 19th century. So, Francis Galton was one of the first people to realise that when we think of numbers, we generally order them on a horizontal line so across the page and usually from left to right.  So maybe I can actually get you to do it.  So, think of a ruler. Think of where number 6 is in the position on the ruler. Now, I'm going to tell you a number. If the number is smaller than the number 6, I want you to raise your left hand. If it's larger than the number 6, I want you to raise your right hand. So, think of number 6, 8. Now...

Graihagh - I raised my right hand. I did it right?

Hannah - You did and you were really fast. Now, think of number 6. If the number I say is smaller, I want you to raise your right hand. If the number is larger, I want you to raise your left hand. 4...

Graihagh - I did have to think about it this time though. I raised my right hand, but I did have to think about it.

Hannah - Exactly! That's because it's much easier for people to order things that get larger so that grow in magnitude from left to right.

Graihagh - And that's the same in chicks as well then.

Hannah - Yes. It turns out that they show the same behaviour.

Graihagh - Imagine you're in a box. There's a card in the middle of the box which 5 dots on it. Behind it is a tasty treat. This happened again, and again, and again. A card with 5 dots is always in the middle. Then one day, there's two cards - one on your left, one on your right, both have two dots on them. Which one do you look behind for your tasty meal worm reward? Well, the chicks nearly always picked the one on the left. Maybe chicks are all left-winged. So, in the next tests, they added two cards with 8 dots on them - one on the left, one on the right, same layout, different dots. Guess what? They looked behind the right card for their reward. This shows that chicks like humans associate lower numbers on the left and higher numbers on the right.

Hannah - In humans, we know that this is because the right hand side of our brain is very dominant. So, we pay attention to the left hand side of pictures. This seems to be the same in chickens as well.

Graihagh - I find this quite surprising that we share this attribute with chicks because surely, that means that the reading of numbers from left to right isn't a cultural thing. It's built in us because we split from birds 300 million years ago or something. Why might we share this with birds?

Hannah - Well, I think that's a question that those researchers are still going to try and find out. It may be that we have some very ancient shared ancestry where the wiring of our brain is very similar way back in evolutionary history.

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