Comparing cognition in humans and other animals
“When a worm is suddenly illuminated,” Charles Darwin wrote, it “dashes like a rabbit into its burrow.” But if you keep scaring it, the worm stops withdrawing. Such apparent learning suggested to Darwin “the presence of a mind of some kind.” Watching as worms evaluated the suitability of objects for plugging their burrows, Darwin offered that worms “deserve to be called intelligent, for they then act in nearly the same manner as a man under similar circumstances.”
But what is intelligence? Nearly everyone agrees that dolphins are intelligent, but not everyone agrees on what intelligent means, or what intelligence is.
In the 1970s, Louis Herman’s group showed that Hawaiian bottlenose dolphins can respond correctly when shown an arbitrary symbol (not a literal picture) for “ball,” followed by a symbol for “question.” If there was no ball, they would press a “No” lever. This demonstrated that a dolphin can form a concept of a ball, and use a symbol to represent “ball.” It showed that dolphins are, as long suspected, very intelligent. Whatever “intelligent” means.