Even animals can make rational decisions

These animals exhibit so-called "executive control" when it comes to making decisions, consciously considering their goals and ways to achieve them before acting, according to researchers at the University of Houston in the US.

Previous research has shown that animals can remember specific events, use tools and solve problems.

However, exactly what that means – whether they are making rational decisions or simply reacting to their environment through mindless reflex – remains a matter of scientific dispute.

Language is required for some sophisticated forms of metacognition, or thinking about thinking, said Cameron Buckner, assistant professor at the University of Houston.

However, bolstered by a review of previously published research, Buckner concluded that a wide variety of animals – elephants, chimpanzees, ravens and lions, among others – engage in rational decision-making.

"These data suggest that not only do some animals have a subjective take on the suitability of the option they are evaluating for their goal, they possess a subjective, internal signal regarding their confidence in this take that can be deployed to select amongst different options," he said.

Language remains a key differentiator, and Buckner noted that serious attempts in the 1970s and '80s to teach animals human language found that although they were able to express simple ideas, they did not engage in complex thought and language structures.

Ancient philosophers relied upon anecdotal evidence to study the issue, but today's researchers conduct sophisticated controlled experiments.

In the new study published in the journal Philosophy and Phenomenological Research, Buckner offers several examples to support his argument.

Matriarchal elephants in Kenya's Amboseli National Park are able to determine the threat level of human intruders by differentiating ethnicity, gender and age, Buckner said.

This suggests an understanding that adult Maasai tribesmen sometimes kill elephants in competition for grazing or in retaliation for attacks against humans, while Kamba tribesmen and women and children from both tribes do not pose a threat, he said.

In another example, Buckner noted that giraffes are not generally considered prey by lions in Africa, due to the long-necked animals' ability to deliver skull-crushing kicks.

However, lions in South Africa's Selous Game Reserve are reported to have learned that giraffes found in a sandy river bed can get stuck and even trip, making them suitable prey.

This suggests an understanding that adult Maasai tribesmen sometimes kill elephants in competition for grazing or in retaliation for attacks against humans, while Kamba tribesmen and women and children from both tribes do not pose a threat, he said.