Carla Krachun, a primate expert at Memorial University of Newfoundland, Canada, who was not involved in the study, and her colleagues had previously shown that chimpanzees could overcome an optical illusion of small grapes looking bigger due to magnifying lenses. "It's extremely interesting that they found similar performances across all species," she says in an email to The Dodo.
Apes that see through deception have a leg up, evolutionarily speaking - the natural world is full of things that aren't what they appear. "Camouflage and mimicry are obvious examples," Krachun says, or "objects appear bigger when immersed in water, or appear a different color under different lighting conditions." And mistaking a snake for a branch, for example, could have lethal consequences.
Krachun believes studies like these could help shed light on the way reality and appearance clash in the social world, too. "Other individuals may misrepresent their feelings, intentions, abilities, identity," she says. "And knowing this would allow one to avoid being misled by others, and also to mislead others to one's own advantage."