美国科学60秒 SSS 2013-08-07（在线收听）

　　have you ever run into a former companion and discover you can't remember his name? this awkward situation is apparently alien to dolphin, who can recall old companions up to 2 decades later. as a recent 60 second science xx explained, dolphins have signature resource that may serve individual names. but how long do they remember their friends titles? to find out, researchers looked at 43 captured dolphins that have moved among the same 6 facilities, living together in different combinations experience times. when the scientist play unfamiliar signature resource for each dolphin, the test subject quickly xx bored. but when the dolphins have recalled the signature resource of the former companion, they move towards the speakers and even xx back of them. the study is in proceeding xx the real society of London b. not even a separation of 20 years could dim the memory of one particular dolphin, which suggests these mammals may have lifelong social memories. perhaps it's time to change the old deccim about elephants to a dolphin never forgets.