Dolphins perform analogous task to pigeons. One object is placed in the water and then they have a choice of three objects. Dolphin obtains information about the identity of the objects using its biological sonar.
Dolphins also show evidence of accumulating information over successive glimpses of the object.
Wearing soft removeable eyecups, the dolphin stationed under water and directed its echolocation clicks at a submerged target located in front of it. Following the dolphin's examination of this target, the object was removed from the water and three other targets were lowered. The dolphin then echolocated on these targets and selected the target that most resembled the sample. The identity of the sample varied randomly from trial to trial and the location of the matching alternative also varied randomly from trial to trial, so the dolphin had to identify and remember the sample in order to correctly chose the matching comparison target.