Baby Chicks Prefer Smaller Numbers on the Left

Posted on January 31, 2015

Scientists have discovered that baby chicks prefer it when smaller numbers are on the left. This is similar to the way humans like to have numbers lined up. The researchers theorize that the number-space mapping in a newborn chick resembles the mental number line (MNL) in humans. This number alignment preference could be a common trait in animals.

In the unusual study scientists from the University of Padova trained 3-day old baby chicks to find mealworms hidden behind white cards that contained small red squares. The researchers then conducted a series of experiments and found that the little chicks tended to go to the left if the card had less red squares than the card they were trained on. They also tended to go right when there were more red squares on the card. For example, if a baby chick was trained on card with five red squares they tended go left (70% of the time) to get the mealworm if presented with a card with fewer squares and right to get the food if presented with a card containing more than five squares.

The scientists say in their report, "The origin of the MNL and its connections with cultural experience are unclear: Pre-verbal infants and nonhuman species master a variety of numerical abilities, supporting the existence of evolutionary ancient precursor systems." The researchers conclude, "Similarly to humans, chicks associate smaller numbers with the left space and larger numbers with the right space."

Tyler Marghetis, a doctoral candidate in psychology at the University of California, San Diego, calls the study "very cool" in a New York Times article. He notes, however, that the finding does not mean the chicks are putting precise numbers in a line but that they are associating "rough quantities" that are smaller or larger with left or right.

A research paper on the baby chicks mental number-line study can be found here in the journal Science.

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