March 4, 2019
Usually, the term, “bird-brain,” is used as an insult—but, at Harvard University, an African Grey parrot named Griffin is rewriting the rules when it comes to avian intelligence, according to a February 25 report by the Harvard Gazette.
It’s not that parrots have been undervalued to date. In fact, talkative and empathetic African Greys are known as the Einsteins of the parrot population.
Now, a study by Harvard psychologists has determined that the African Grey can perform some cognitive tasks with mental agility beyond that of five-year-old humans.
The results not only suggest that humans aren’t the only species capable of making complex inferences, but also point to flaws in a widely used test of animal intelligence. The study is described in a November 2018 paper published online in Behaviour.
The paper arose from a collaboration led by Irene Pepperberg, a research associate in Harvard’s Psychology Department.
The team first employed a classic challenge that uses two cups. A reward is hidden in one of the cups; subjects are then shown that one cup is empty, and those that successfully choose the other cup are thought to employ a process known as “inference by exclusion”—reasoning that if the reward is not in A, it must be in B.
For years, researchers have argued that young children—including infants as young as 17 months, and animals from a wide number of species, including Grey parrots—understand this process.
“This is really about logic,” Pepperberg said. “In the wild, nonhumans must make these kinds of choices when they decide on things like, ‘Where should I forage? I saw other creatures eating food in this area. … If there’s nothing right here, I should deduce that something is nearby.’”
But what’s important about this study is not just that Griffin is, in some ways, as smart as a five-year-old, but, said Pepperberg, “We also argue that this two-cup task, which has been the gold standard, only tells you about a certain level of ability. If you really want to study inference by exclusion, you have to go to the more complicated three- and four-cup tasks.”
Based on the theory that the two-cup task wasn’t an effective test of human cognition—that subjects could be choosing that B cup simply by default, not because they think the reward must be there—the researchers decided to put Griffin’s apparent smarts to a more challenging test.
They performed a three-cup test in which one reward was hidden in a single cup, and another was placed in one of two additional cups to one side of the first cup. When faced with a choice, participants should pick the single cup, as it is the only cup guaranteed to have a reward. This task doesn’t test inference by exclusion, but does test understanding of certainty versus mere possibility — a precursor to exclusion.
A four-cup test worked similarly: Rewards were placed in one cup of each pair; then one cup in a pair was shown to be empty. Successful subjects would then pick the other cup in that pair, understanding that it must hold the reward, and that they had only a 50-50 chance of finding the reward in the other pair. The 30-month-old children again failed, showing that they do not fully understand inference by exclusion.
Although Griffin passed both tests “with flying colors,” the research team still wanted to be sure that he hadn’t simply learned to choose whichever cup was next to the empty one; so they designed a series of additional trials to test this possibility.
“Basically, we forced him to gamble,” Pepperberg said. “For a small percentage of trials, we would put nothing on one side and show him an empty cup on that side … so he if wanted a reward, and understood the system, he’d know that now he couldn’t go to the cup next to the empty one; instead he’d have to gamble on the 50-50 side. And he hated it, but he did it on all the trials in the subset.”
The researchers even developed a test in which he had the choice between the guaranteed small reward of a nut or, in a small percentage of trials, gambling and potentially receiving one of his favorite treats—a Skittle.
“We wanted to make sure he wasn’t just avoiding the empty side completely … and, again, that he didn’t always pick the cup next to the one that was empty,” Pepperberg said. “If he wanted that very special candy, he’d have to go to the 50-50 side. A good-enough percentage of the time, he gambled. But what was interesting was that if he lost, he wouldn’t gamble on the next trial.”
“Birds are separated from us by 300 million years of evolution, and their brains are organized differently than ours,” Pepperberg said. “That’s why this was so exciting — because we were able to show that Griffin was working at the level of a five-year-old, on a task at which even apes would not likely succeed.”
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