Echo Chamber Confidence
We should realize that we gain far less info in an echo chamber than from being around folks with diverse views. The latest Journal of Experimental Psychology says we just don't get this:
The experimental task involved estimating the number of calories in measured quantities of different foods (e.g., a cup of yogurt, a bowl of cooked rice). … Participants were asked to generate a calorie estimate for each food and then indicate their confidence in it. … [Then] they were provided with the opinions of three advisors, and were given the opportunity to revise their initial estimates. They were told that they would receive a bonus for making accurate judgments, … [and] were also asked to indicate their confidence in their final (revised) estimates and to bet on their accuracy. …
On half the trials (independent condition) the [screen] header stated that “these estimates were randomly drawn from a pool of 100 estimates made by participants in a previous study,” whereas on the remaining trials (opinion-dependent condition) the header stated that “these estimates were selected from those closest to your own initial opinion in a pool of 100 estimates made by participants in a previous study.” …
Receiving advice increased participants’ confidence in the dependent condition, but not in the independent condition. Participants indicated greater confidence in their final estimates in the opinion-dependent than in the independent condition. In accord with the confidence results, the participants bet more often in the dependent (58%) than in the independent condition (42%).
Please, please, don't let yourself succumb to the very common bias to confidence in views because "everyone" at your favorite website agrees with them, if those people have been selected for this very agreement! Once you realize that many others elsewhere disagree, that disagreement should weigh heavily on your estimation.
There's a key bit of missing information in your original extract of the study. You mention the heading of where the opinions came from, as presented to the subjects of the study. What isn't mentioned is where the opinions actually came from, and how similar or dissimilar the opinions actually were to the subject's opinions. We are left wondering whether the outcome of the study was due to the headings, or due to the opinions.
Hal, the approach very clearly doesn't work in this context. If it seems to, that suggests an error of reasoning.