The measured findings about communication share one uncomfortable conclusion: a message is not a parcel delivered intact. It changes in transit, it changes in memory, and it lands differently depending on who receives it. The entries in this group are mostly about that gap between what was said and what arrives.
The oldest line of evidence concerns transmission. Bartlett's serial-reproduction experiments of the 1930s, filed here as Chinese Whispers, showed stories growing shorter and more conventional with each retelling. Allport and Postman found rumour following the same path, spreading in proportion to its importance and to the lack of better information. The recent entries extend the pattern to quotation itself: Beam Me Up, Scotty records how the best-known version of a line is often one nobody said. The theme is that retelling edits, and it edits towards the memorable rather than the accurate.
A second group of findings concerns memory, and here the evidence becomes stranger. The Sleeper Effect shows a discounted message gaining force as its source is forgotten. The Illusory Truth Effect shows repetition raising belief even in claims people know to be false. The Continued Influence Effect shows corrected misinformation still shaping inference after the correction is accepted. Read together, they suggest that what a person remembers of a message is its familiarity and its gist, while the label saying whether to trust it fades first.
The third theme is the audience. Partisans on opposite sides rate the same balanced coverage as biased against them, which is the Hostile Media Effect. People believe media influence others more than themselves. A single vivid case outweighs the statistics printed beside it, and a story lowers resistance where an argument would raise it. None of this is peculiar to the uneducated or the credulous; the studies find it across the board.
Where it applies
The practical uses are unusually direct. A reporter choosing which individual to profile is, on the exemplification evidence, choosing how common the audience will think the problem is. A public-health campaign deciding whether to repeat a myth in order to correct it faces a live research question, since the Backfire Effect that once argued against repetition has largely failed to replicate. An advertiser setting a budget meets Peckham's Rule, the observation that a new brand needs more than its target share of advertising voice. A censor meets the Streisand Effect.
The most useful application is personal. Gell-Mann Amnesia, Crichton's name for trusting coverage in fields one does not know after seeing its errors in a field one does, is less a finding than a prompt. Every entry here describes something that happens to the reader, and the third-person effect predicts that the reader will assume it happens mainly to others.
Where it is argued over
The group contains some of the best-replicated results in the subject and some of the least. Illusory truth and continued influence have held up well. The backfire effect is now cited chiefly as a caution about how fast a striking finding travels. Selective Exposure is real as a preference, but researchers who study actual media diets argue that popular talk of echo chambers overstates it.
Two entries carry a different kind of dispute. Sealioning names a tactic of exhausting an opponent with polite demands for evidence; its critics point out that the label can itself be used to dismiss legitimate questions. Sailer's Law of Neologisms makes a testable claim about which coinages spread and has not yet been tested. Both show the ledger's rule at work: a claim is filed with its standing, whoever made it.
Why it is worth knowing
These findings form the evidential floor of the subject. The models in the next essay make large claims about media power; the evidence here says what has been measured, and so which of those claims have something to stand on. They also correct a common picture of persuasion as a contest of arguments. Much of what moves belief is repetition, vividness, familiarity and the fading of a source, none of which is an argument at all.
Knowing this does not grant immunity. It does give a reader a short list of questions worth asking about any claim they find themselves believing: where it came from, how often they have heard it, and whether they remember the correction as clearly as the claim.
The entries behind this essay: Evidence in Communication & Media. Every subject has its essays on the essays page.