You better watch who you're calling "bird brain." A new study in the journal Science suggests that some birds are smarter than we realised.
The study, which was conducted by zoologists Antone Martinho III and Alex Kacelnik at Oxford University, found that newborn ducklings are capable of comprehending complex concepts such as "same" and "different" - abstractions that we typically think are beyond the capacity of most animals.
"The claim that abstract relational thinking is a unique ability of human beings can no longer be supported," University of Iowa experimental psychologist Edward Wasserman wrote in an accompanying analysis.
"Although animals may not be able to speak, studying their behaviour may be a suitable substitute for assaying their thoughts, and this in turn may allow us to jettison the stale canard that thought without language is impossible."
To interpret ducklings' thoughts, Martinho and Kacelnik tossed them into an experiment the day they were born. The experiment relied on the animals' ability to imprint - to identify such significant figures as their mothers, very soon after birth.
Once a duckling imprints, it sticks with that "mother" steadfastly, trailing her.
This is true even when that object is not actually a duck. In Martinho and Kalcelnik's study, the ducklings were introduced 24 hours after hatching to a pair of small, brightly coloured shapes that circled above their pens like objects on a mobile. Some pairs had identical shapes - two spheres, for example - while others had mismatched ones. This was the "priming period" for what the researchers termed a "same-different" test.
Next, the baby birds were exposed to two new pairs of objects, one with the same shapes, the other with different ones. The majority of ducklings followed the pair of shapes that had the same relationship as the pair with which they were primed.
The same principle held when the researchers tweaked the experiment, alternating the colour of the two objects in the pairing rather than the shapes. Ducklings that had been primed with objects of the same colour opted to follow a different one-colour pair later in the experiment; those that had been primed to recognise a pair with two colours did the same.
The results suggest that ducklings are able to recognise not only shape and colour but also sameness and difference - abstract concepts that require a complex understanding of the way things relate to one another. That the objects were in motion makes interpreting these relationships even more difficult.
"Even in a seemingly rigid and very rapid form of learning such as filial imprinting," the researchers wrote, "the brain operates with abstract conceptual reasoning, a faculty often assumed to be reserved to highly intelligent organisms."
According to Martinho and Kacelnik, previous studies have found that other animals, such as primates and crows, can understand these concepts. But they have to be taught.
"To our knowledge, this is the first demonstration of a non-human organism learning to discriminate between abstract relational concepts without any reinforcement training," Kacelnik said.
If the ducklings just had a visual 'snapshot' of their mother, they would lose her
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It's an impressive ability, Martinho added, but it also makes biological sense that ducklings would have it.
"Ducks walk, swim and fly and are constantly changing their exact shape and appearance as they extend their wings or become partially submerged. . . . If the ducklings just had a visual 'snapshot' of their mother, they would lose her," he said.
"They need to be able to flexibly and reliably identify her, and a library of concepts and characteristics describing her is a much more efficient way to do so, compared with a visual memory of every possible configuration of the mother and her environment."
Wasserman has said abstract thinking is far more widespread in the animal kingdom than we give other creatures credit for.
He has done research with rats showing they're capable of learning to understand sameness and difference and with crows suggesting they can be taught to match stimuli by colour, shape and number of objects.
Other examples are mounting: In one study, honeybees were taught to distinguish between paintings by Monet and Picasso.
"Our research and others suggest abstract concepts, as tools for thought, are not a luxury," Martinho told PBS. "A lot of vertebrates are going to need them if they're going to have a flexible, robust understanding of the world around them."