for belief are powerful, they are also subject to superstition, manipulation, and fallacy. This is not trivial stuff: beliefs, and the imperfect neural tools we use to evaluate them, can lead to family conflicts, religious disputes, and even war.
In principle, an organism that trafficked in beliefs ought to have a firm grasp on the origins of its beliefs and how strongly the evidence supports them. Does my belief that Colgate is a good brand of toothpaste derive from (1) my analysis of a double-blind test conducted and published by
*Animals often behave as if they too have beliefs, but scientific and philosophical opinion remains divided as to whether they really do. My interest here is the sort of belief that we humans can articulate, such as 'On rainy days, it is good to carry an umbrella' or 'Haste makes waste.' Such nuggets of conventional wisdom aren't necessarily true (if you accept 'Absence makes the heart grow fonder,' then what about 'Out of sight, out of mind'?), but they differ from the more implicit 'beliefs' of our sensorimotor system, which we cannot articulate. For example, our sensorimotor system behaves as if it believes that a certain amount of force is sufficient to lift our legs over a curb, but nonphysicists would be hard pressed to say how much force is actually required.) I strongly suspect that many animals have this sort of implicit beliefs, but my working assumption is that beliefs of the kind that we can articulate, judge, and reflect upon are restricted to humans and, at most, a handful of other species.
Because evolution built belief mainly out of off-the-shelf components that evolved for other purposes, we often lose track of where our beliefs come from — if we ever knew — and even worse, we are often completely unaware of how much we are influenced by irrelevant information.
Take, for example, the fact that students rate better-looking professors as teaching better classes. If we have positive feelings toward a given person in one respect, we tend to automatically generalize that positive regard to other traits, an illustration of what is known in psychology as the 'halo effect.' The opposite applies too: see one negative characteristic, and you expect all of an individual's traits to be negative, a sort of 'pitchfork effect.' Take, for example, the truly sad study in which people were shown pictures of one of two children, one more attractive, the other less so. The subjects were then told that the child, let's call him Junior, had just thrown a snowball, with a rock inside it, at another child; the test subjects then were asked to interpret the boy's behavior. People who saw the unattractive picture characterized Junior as a thug, perhaps headed to reform school; those shown the more attractive picture delivered judgments that were rather more mild, suggesting, for example, that Junior was merely 'having a bad day.' Study after study has shown that attractive people get better breaks in job interviews, promotions, admissions interviews, and so on, each one an illustration of how aesthetics creates noise in the channel of belief.
In the same vein, we are more likely to vote for candidates who (physically) 'look more competent' than the others. And, as advertisers know all too well, we are more likely to buy a particular brand of beer if we see an attractive person drinking it, more likely to want a pair of sneakers if we see a successful athlete like Michael Jordan wearing them. And though it may be irrational for a bunch of teenagers to buy a particular brand of sneakers so they can 'be like Mike,' the halo effect, ironically, makes it entirely rational for Nike to spend millions of dollars to secure His Airness's endorsement. And, in a particularly shocking recent study, children of ages three to five gave have higher ratings to foods like carrots, milk, and apple juice if they came in McDonald's packaging. Books and covers, carrots and Styrofoam packaging. We are born to be suckered.
The halo effect (and its devilish opposite) is really just a special case of a more general phenomenon: just about anything that hangs around in our mind, even a stray word or two, can influence how we perceive the world and what we believe. Take, for example, what happens if I ask you to memorize this list of words:
Now read the following sketch, about a man named Donald:
Donald spent a great amount of his time in search of what he liked to call excitement. He had already climbed Mt. McKinley, shot the Colorado rapids in a kayak, driven in a demolition derby, and piloted a jet-powered boat — without knowing very much about boats. He had risked injury, and even death, a number of times. Now he was in search of new excitement. He was thinking, perhaps, he would do some skydiving or maybe cross the Atlantic in a sailboat.
To test your comprehension, I ask you to sum up Donald in a single word. And the word that pops into your mind is . . . (see the footnote).* Had you memorized a slightly different list, say,
*Due to the effects of memory priming,
ferent — and people tend to pick a characterization that relates to what was already on their mind (in this case, slyly implanted by the memory list). Which is to say that your impression of Donald is swayed by a bit of information (the words in the memory list) that ought to be entirely irrelevant.
Another phenomenon, called the 'focusing illusion,' shows how easy it is to manipulate people simply by directing their attention to one bit of information or another. In one simple but telling study, college students were asked to answer two questions: 'How happy are you with your life in general?' and 'How many dates did you have last month?' One group heard the questions in exactly that order, while another heard them in the opposite order, second question first. In the group that heard the question about happiness first, there was almost no correlation between the people's answers; some people who had few dates reported that they were happy, some people with many dates reported that they were sad, and so forth. Flipping the order of the questions, however, put people's focus squarely on romance; suddenly, they could not see their happiness as independent of their love life. People with lots of dates saw themselves as happy, people with few dates viewed themselves as sad. Period. People's judgments in the dates-first condition (but not in the happiness-first condition) were strongly correlated with the number of dates they'd had. This may not surprise you, but it ought to, because it highlights just how malleable our beliefs really are. Even our own internal sense of self can be influenced by what we happen to focus on at a given moment.
The bottom line is that every belief passes through the unpredictable filter of contextual memory. Either we directly recall a belief that we formed earlier, or we calculate what we believe based on whatever memories we happen to bring to mind.
Yet few people realize the extent to which beliefs can be contaminated by vagaries of memory. Take the students who heard the dating question first. They presumably
