Are Animals People?

Research Blogging / by Dave Munger /

The disparity between experiments that suggest sophisticated cognition in animals and those that find hard limits to animal intelligence has created a debate over animal “personhood.”

The recent fatal attack of a SeaWorld trainer by the orca Tilikum has led to renewed questions about how humans should deal with potentially intelligent animals. Was Tilikum’s action premeditated, and how should that possibility influence decisions on the animal’s future treatment? Orcas, like their close relatives, dolphins, certainly seem smart, though researchers debate just how intelligent these cetaceans are and how similar their cognition is to humans. Should we ever treat such creatures like people?

For centuries it seemed obvious to most people what separated them from other animals: Humans have language, they use tools, they plan for the future, and do any number of things that other animals don’t seem to do. But gradually the line between “animal” and “human” has blurred. Some animals do use tools; others solve complicated problems. Some can even be taught to communicate using sign language or other systems. Could it be that there isn’t a clear difference separating humans from other life forms?

Last week, Brian Switek, a science writer who blogs about biology and paleontology, found a study demonstrating that tool use in chimpanzees isn’t a new phenomenon. For decades, scientists have been observing chimps using sticks and other objects as tools. They have even seen chimps modifying these tools and transporting them for anticipated use in the future. But until recently, there had been no evidence that tool use among chimps had a very long history. Wild chimpanzees in the Tai National Park in Côte d’Ivoire have been observed using stones as hammers and anvils for cracking large nuts. A team led by archaeologist Julio Mercador found evidence that these tools were being used as long as 4300 years ago: Ancient stones shaped similarly to those being used today as tools. Their research was published in PNAS in 2007.

But how did the scientists know that these were purpose-made tools and not just bits of rock that had been shaped by erosion or other means? The researchers created a test, mixing the “tools” with other similar rocks and showing them to other chimpanzee experts, who had to pick out the genuine tools. They were able to do this with over 90 percent accuracy, suggesting that the rocks Mercador’s team had found were legitimate tools, evidence of a chimpanzee “stone age” that continues to this day.

But evidence of human-like intelligence is found in other parts of the animal kingdom as well. Consider the case of dolphins. Graduate student Jason Goldman and post-doctoral fellow Daniel Bassett have both blogged about an article published in Science, recapping a session at their annual conference last month. Dolphins have very complex brains that, in proportion to body size, outclass even the large-brained great apes. They can be trained to communicate and have demonstrated very sophisticated problem-solving strategies. Dolphins also have spindle neurons, which are associated with emotion in humans. This led philosopher Thomas White to conclude that dolphins possess all the traits of personhood, and should be considered “non-human persons.”

Goldman isn’t so sure. Dolphins don’t appear to have a human sense of morality, as some have been witnessed regularly engaging in rape and infanticide. On the other hand, there are certainly unsavory and immoral human individuals as well. Spindle neurons might not serve the same function in dolphins as they do in humans—and, to my knowledge, no study has tested that they do.

Even though many animals have demonstrated some human-like abilities, other studies have shown their limitations. John Beetham writes a well-crafted blog about birding in New Jersey and Washington, DC, and last month he discussed a fascinating study of the very intelligent New Caledonian crow. The study, published in PLoS ONE in February, was led by Alex Taylor.

The researchers built a perch for the crows above a small hole. A string was fastened to a rod and dangled through the hole. The crow, standing on the perch, could see a piece of meat tied to the end of the string, but couldn’t tell how big or far away the meat was. Crows that had been presented with a similar conundrum in earlier experiments, where the meat and string were easier to see, readily solved the problem by hauling up the string using their feet and beaks. But naive crows struggled with the task, figuring out how to retrieve the meat only through an arduous process of trial and error. However, if a mirror was placed next to the apparatus so they could see how it worked, they figured it out just as quickly as the experienced crows. Thus, Taylor’s team argues, the crows aren’t using any special insight to solve the task, but relying either on visual feedback or conditioned learning. Maybe crows aren’t so smart after all.

Similarly, I reported on a study of chimps last year showing that while they have some ability to understand what other chimps are thinking, this ability appears only a bit more sophisticated than three-year-old humans, and is bested by human six-year-olds.

So while many animals display remarkable cognitive abilities, there are clearly limits to what they can do. Does this mean they aren’t entitled to be considered “non-human persons?” Is it even appropriate to judge non-human animals in such anthropomorphic terms? Suppose we decide it’s wrong to keep an orca in captivity because of its intelligence. Then what about a slightly less-intelligent animal like a pig or a dog? Where do you draw the line? These questions are still up for debate—and as the debate continues, you can follow along on

Front page image courtesy of Linda Tanner.

Originally published March 17, 2010


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