In the Sally-Anne false belief test conducted on children, a puppet named Sally places a marble in a box, then leaves the room. Next, a puppet named Anne enters the room and moves the marble to a cupboard. When Sally returns, the child is asked where Sally will look for the marble. Up to the age of three, children invariably　answer “the cupboard.” Between the ages of four and six, however, children begin to appreciate that Sally doesn't know that the marble has been moved. This demonstrates a concept referred to as “theory o mind”-the recognition that beliefs are based on experience, and therefore different people will interpret events differently.
   Are humans unique in possessing a theory of mind? An adapted form of the Sally-Anne test was recently conducted en dolphins at Sea World in Durban, South Africa. Two cooler boxes were placed next to the dolphin tank, hidden from the dolphins by a plastic screen. While head trainer Gabby Harris watched from nearby, another trainer placed a fish in one of the boxes. Then the screen was removed and Harris tapped on the box containing the fish. The dolphins soon learned that if they touched that box with their noses, they got to eat the fish.
   After several trials, the pattern changed. Harris turned away from the box and appeared to be distracted by something after the
screen was removed. Meanwhile another trainer switched the boxes so that when Harris turned around, she was tapping on the wrong box.
   Four different dolphins in four different trials all got it right-that is, they went to the box that Harris didn't tap. “They usually followed my commands,” says Hanis, `but they realized that, in this instance. I’d made a mistake.”
   These dolphins are the first nonhumans to pass a false-belief test, a generally recognized indicator of advanced cognitive abilities in humans. The ethical question is: If dolphins are able to show higher cognitive capacity, do they deserve to be treated more like humans?