Bayes' Rule

How do people integrate or ignore new information based on their existing beliefs? Bayes' Rule. Or at least that's according to a study I'm reading that offers a mathematical formula to sum it all up:

P(A/B) = P(B/A) P(A) P(B)

That settles everything. Right? Wait, don't click that mouse!

Let's break it down, at least according to the article (abstract here). A = your existing belief, B = new information. The new belief, the stuff to the left of the equals sign above, is equal to the product of our prior belief and "the likelihood that B would occur if A was true."

Confused? Me too. Forget the math. Thankfully a graph or two later the authors tell us Bayes' Rule "does not provide a complete normative standard." Translation: it doesn't work all that well in the real world.

The study as a whole has to do with discomfirmation biases, how we selectively deal with information, which is obviously of interest to anyone studying political communication and how people make sense of their political world. Basically they find people cannot ignore their prior beliefs when dealing with new information. People see congruent arguments (ones that fit their own beliefs, called congruence bias) to be stronger -- even if they're not.

Some other interesting results: sophistication (often a function of political knowledge) can moderate disconfirmation bias (but not congruence bias). In other words, politically knowledgeable folks are a little less likely to disbelieve a message that is against their beliefs as compared to those who are less knowledgeable, but it plays no role in how people judged messages that agreed with their point of view as being stronger than it actually is.

I hope that made sense.

Meaning Making

We all engage in meaning making. Scholars from widely different fields have widely different approaches to the question of how people make sense of their social and political world. Most of us use some form of heuristics, rules-of-thumb, shortcuts, schemata, chronically accessible constructs, and a host of other theoretical fictions to help us tame the information tide (to borrow a book title). I'm sure there are others I've missed, but they all share in common the idea that we can't possibly cope with the world in all its complexity, so we find shortcuts to help us make sense of what we see and hear (and taste, and smell, and feel, if I want to be fair to all the senses).

These are more than mere shortcuts -- they come rich with meaning. We impress meaning on what we see and hear and then fit it to our own expectations and predispositions. Doesn't fit? Oh, we'll make it fit, we'll get that round peg into a square hole even if we have to change what we actually heard or saw. Selective attention, meet selective memory.

Why am I going on about this? In part because I've been reading student papers from my Public Opinion graduate seminar, in part because I've been reading the "who hates the most, liberals or conservatives?" nonsense on the web and papers, and in part because I needed blog material for today.

But it comes down to this: What people know, unfortunately, is often a function of what they want to know, or what they want it to mean.