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Science Communication


Equine e-readers and Paleolithic calendars

by Katherine Bourzac
January 29, 2023 | A version of this story appeared in Volume 101, Issue 4


Horses get screen time

A brown horse stretches its nose toward a touchscreen. The screen is bisected by a wooden stick and displays the letter "V" on one side and the letter "X" on the other. The horse's nose is on the "X" side. Below the screen, a tube leads to a small food bowl. A wall made of wooden planks is in the background.
Credit: Animals
Pony picks: A horse hoping for a carrot treat selects the letter X.

After more than 5,500 years of domestication, horses have gotten good at reading human faces. Their social skills can even interfere with scientific studies of their cognition. Humans often accidentally cue horses on the right answers to cognitive tests, an effect called the Clever Hans Phenomenon. Hans, a horse that lived in Berlin in the early 20th century, appeared to be able to perform arithmetic, tapping his hoof to give answers. But in 1907, psychologists discovered that he was deciphering signals in questioners’ facial expressions to provide the correct sum. When a questioner’s face was hidden, Hans was not so clever.

California Institute of Technology psychologist Tetsuro Matsuzawa is experimenting with technological fixes to take human bias out of horse cognition studies. Instead of tapping their hooves, horses in his study tap their noses to touchscreens (Animals 2022, DOI: 10.3390/ani12243514). Unlike people, the screens don’t give the animals any untoward clues.

Researchers tested the equine e-reader in a group of five endangered ponies called Garrano horses. The scientists first taught the horses how to use the touchscreen: if they touched a black dot with their noses, a carrot cube of about 2 g was dispensed into a feeder bowl.

The researchers then tested whether the animals could distinguish the letters O, B, V, Z, and X in Arial font (the ponies’ potential preferences for other fonts were not investigated). A wooden divider bisected the touchscreen, so the horses could touch only one side at a time. The letters were introduced one at a time, with one or the other of a pair of letters cued as the right answer with a chime and a carrot snack. If the horse touched the wrong letter, it triggered a buzzer sound—and no treat.

The four female ponies in the group shone at the letter discrimination task. Even Kiki, a 2-year-old who still needed care from her mother, and Flore, who had no sight in her right eye, could do it. The researchers write that Boneko, a castrated male who “behaved like a stallion in a feral group,” didn’t perform as well. But more data are needed to draw any conclusions about how age or sex affects horses’ visual cognition and reading skills.


Decoding Paleolithic art

A drawing of a cow-ike animal with long horns. The animal is drawn in outline in black and has four black dots in a horizontal row in the middle of its back.
Credit: JoJan/Wikimedia Commons
Ancestral accounting: Anthropologists are studying paintings like this aurochs in Lascaux cave in France.

For Paleolithic humans, horses were an important food source and an artistic inspiration. Dating as far back as 37,000 years ago, people decorated European caves with hauntingly beautiful images of horses, mammoths, ancestral cattle called aurochs, salmon, and other prey.

These animals are often decorated with abstract signs. Lines, dots, and Y-shaped symbols occur in about 66% of animal art from the late Paleolithic. Anthropologists have puzzled over their meaning for 150 years.

In a painting of a horse in the Chauvet cave in France, for example, the delicately shaded creature sports three red splotches on its muzzle. Another horse, found in the country’s Lascaux cave, has two Y-shaped signs along its hairy belly. A red deer bounding along the wall has seven red dots in a straight horizontal line over its antlers.

What were our hunter-gatherer ancestors trying to convey with these marks? A new paper proposes that these illustrations are a kind of calendar. A group led by University of Durham psychologist Robert Kentridge hypothesizes that the marks record information about the life cycles of these prey animals. “Information pertinent to predicting their migratory movements and periods of aggregation, i.e. mating and birthing . . . would be of greatest importance for survival,” the authors write (Cambridge Archeol. J. 2023, DOI: 10.1017/S0959774322000415).

They suggest that the total number of marks could denote the number of months after the start of the year that an event such as breeding season occurs. Hunter-gatherers could have counted months by observing the moon’s cycle and might have marked the beginning of the year as the time when the snow began to melt.

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