抄録
Dolphins are known to exhibit highly developed social interactions, and numerous high advanced social behaviors have been observed in their school. We conducted a variety of tasks to understand the cognitive abilities of beluga (Delphinapterus leucas). Symmetry, a cognitive ability that is only present in a few nonhuman animals, was tested in a male beluga ten years ago (1997). At that time, however, it was found that the subject performed poorly. Here we report the results of our observations which set about to determine whether cognitive mechanisms, such as symmetry, could be altered or developed over a relatively long period of time (i.e. 10 years). We used the same beluga that was used for the symmetry tests conducted 10 years previously. Using the same procedures employed in the first test, the subject was observed to exhibit symmetry. Since the subject has been engaged in a variety of cognitive tasks other than tests of symmetry over the past 10 years, it is proposed that these experiences have positively influenced the development of symmetry in this animal.
