By Kim Tae-gyu
Staff reporter
A multinational investigation team composed of experts from the United States, the United Kingdom, Sweden and Australia, as well as South Korea concluded late last month that the Navy frigate Cheonan sank on March 26 due to a North Korean torpedo attack.
A vast majority of countries accepted the explanation backed by convincing evidence but many South Koreans seemingly remained doubtful. Rather, they turned to online posts, which alleged the Seoul administration fabricated evidence.
Domestic observers point out that the phenomenon is caused by the "sleeper effect," under which people tend to trust a message from low-credibility sources some time after they learned of it.
"Most people do not advocate even a persuasive message if it comes together with a discounting cue, or incredible sources, such as rumors on the Web," said a professor at a Seoul-based university.
"After some time passes, however, people forget about the source and remember just the persuasiveness of the message. Then, they believe in it and this is called the sleeper effect. I think the effect is behind the distrust on the Cheonan case."
Media Research, a local public opinion pollster, commissioned a survey in late May on the announcement of the sunken navy ship. To the surprise of the government, 24 percent of respondents said that they did not trust the official report.
This means that more than 10 million of the country's 48 million population are suspicious about the in-depth investigation by a multinational team, comprising both private experts and government officials.
North Korea reportedly used identity theft of South Korean people to upload a flurry of posts to contend that the South manipulated the evidence and the North had nothing to do with the case. The anonymous professor said that such a maneuver would have also played a role in creating the sleeper effect.
The sleeper effect, discovered by Yale University psychologist Carl Iver Hovland in the early 1950s, has also been seen nationwide in the lead up to Wednesday's local elections.
"During the election campaigns, various rumors circulate about candidates. At first people typically do not believe them. But when they are casting votes, they often find themselves affected by hearsay," the professor said.
Ever since the idea of the sleeper effect appeared around 60 years ago, debate has continued as to whether the phenomena take place often or is observed under only very unusual circumstances.
Some contend that the hypothesis is seen across the world while others discount the assumption, claiming that it is too counterintuitive that low-credibility sources eventually win out.