This is despite the fact that when the same report is presented in another format (as an essay, for example) it is assumed to be neutral, or even supportive of the reader’s view.
The effect is particularly apparent when the report concerns some sort of conflict and the viewer is already aligned to one side. Interestingly, it doesn’t matter which side, the bias will be attributed to the opposition regardless. When neutral people view the report, bias is rarely reported.
Serious psychological study of perceived media bias began in the mid-1980s with studies by Vallone, Ross, and Lepper, and by Perloff. In both studies, pro-Israeli and pro-Palestinian participants were presented with television news coverage of Israel’s invasion of Lebanon and subsequent fighting. The pro-Israeli participants believed that the coverage was biased in favor of the Palestinians, and that it would make neutral observers feel less favorable towards their side, while the pro-Palestinians were convinced the coverage was biased in favor of the Israeli side, and that it would hurt their image in the eyes of neutral observers. This is despite the fact that when neutral observers did view the coverage, in Perloff’s study, they failed to perceive any bias, and their opinions of the two sides stayed the same.
As always, there’s more careful analysis and detailed references to the supporting research in the full post on Mixing Memory.
Link to ‘Hostile Media Effects’ on Mixing Memory.