Baby chicks seem to have a number sense and may be able to count from left to right just like humans, a new study suggests.
Scientists found that chicks seem to count upwards moving from left to right - they put smaller numbers on the left and larger numbers on the right, the same mental representation of the number line that humans use.
Most people learned about number lines in math class, with smaller numbers coming from the left and increasing as they go right, researchers said.
That same way of thinking about numbers seems to be embedded in people's mental representations of numbers, researchers added. However, the reason for this is not known.
To help understand mental representation of numbers better, lead author Rosa Rugani, a psychologist at the University of Padova in Italy and her colleagues trained 3-day-old chicks to travel around a screen panel with five dots on it to get to a tasty food treat behind it.
This made the five-dot panel an anchor number that the chicks could compare the other numbers to.
After the chicks learned that the five-dot panel meant food, the researchers removed that panel, and then placed the chicks in front of two panels, one off to the left and the other off to the right, that each had two dots, 'Live Science' reported.
They found that the chicks tended to go to the left panel, suggesting that the chicks mentally represent numbers smaller than five as being on the left of five.
When the researchers put the chicks in front of two panels that each had eight dots, the chicks walked to the panel on the right.
This suggests the chicks mentally represent numbers larger than five as being on the right of five, the researchers said.
In a second experiment, the researchers repeated the whole process, but started with a panel that had 20 dots (instead of five). They then added two other panels that had either eight or 32 dots.
The baby chicks tended to go to the left when the screens had just eight dots, and to the right when they had 32 dots, according to the study in the journal Science.
"They associate small numbers with the left space and larger number with the right space, and this resembles the humans' behaviour in responding to numbers," Rugani said.
The findings suggest the chicks were conceptualising the number line with smaller numbers on the left, just like humans, the researchers said.
That, in turn, may suggest the mental representation of numbers emerged many millions of years ago, in an organism that was a common ancestor to both birds and humans.
