Pigeons learn to put complicated images into categories by focusing on details that matter and ignoring irrelevant features.
The ability to extract important information from a busy environment has long been thought to be a hallmark of human intelligence. The new findings suggest that pigeons, and likely other creatures too, are also able to make quick decisions about which objects belong in certain groups.
By helping animals distinguish between predators and harmless creatures or between nutritious food and poison, the skill can be a matter of survival.
"If you learn that cats and dogs are more or less dangerous, you won't have to worry about the breed of cat or color of dog," said Edward Wasserman, a psychologist at the University of Iowa in Iowa City. "You can attend to the dogness or catness and you don't have to use all of your memory on individual examples. You can use these essences and say, 'That has catness. That's good enough. I'm out of here.'"
"Most people would credit pigeons with little intelligence, but we've been studying them for 40 years and they seem to engage in highly complex visual tasks that require a considerable amount of learning," he added. "We need a dose of humility in our evaluation of other species."
When people determine whether an object belongs to a group such as "chair," "car" or "bread," they pick out the features that object shares in common with others in the group while filtering out all the things that make each member of the group different from all the others.
The ability to categorize allows for efficient decision-making and even paves the way for language, allowing us to distinguish between units of sound.
Previous studies have demonstrated that pigeons can put objects into groups but it's been unclear how they do it. To find out, Wasserman and colleague Leyre Castro used a touch screen to show a series of images to eight pigeons.