Elephants keep surprising us.

They live complex social lives, cooperate, show altruism and grieve their dead. And now in the latest evidence of their sophisticated cognitive abilities, elephants appear to be able to distinguish relative amounts of food merely by smell, researchers say. The finding, reported Monday in Proceedings of the National Academy of Sciences, suggests that elephants’ olfactory worlds are richer and more informative than ours.

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Many tests of animal cognition rely on vision — an elephant or a crow is shown, say, two buckets with different amounts of food, and prompted to choose between them. Some species do quite well at this task, suggesting they can make visual estimates of quantity. Others don’t seem to notice the difference. But such visual tests overlook that other senses, like smell and hearing, may be even more important to how some animals navigate the world.

Elephants raise their trunks up like a submarine periscope to sniff their environment, potentially gathering information to aid in decision making, said Joshua Plotnik, a professor of psychology at Hunter College in New York, an author of the new study. To see if elephants could distinguish different amounts of food using only scent, Dr. Plotnik and his colleagues devised a series of experiments that were performed at the Anantara Golden Triangle Elephant Camp and Resort in Chiang Rai, Thailand.

Six Asian elephants were presented with pairs of plastic buckets, one of which had more sunflower seeds than the other, in a range of ratios. The buckets were covered with lids that the elephants could not see through, but with holes that smells could escape through. The elephants were allowed to choose one bucket to open and eat.