I am, by nature, an optimist. I almost always think things will turn out well, and even when they break I am confident that I can fix them. My optimism, however, has not always served me well. Twice I have been hit by cars while cycling—full-on, through-the-windshield impacts that were entirely the result of my blissful attitude that the street corners I had successfully negotiated hundreds of times before would not suddenly materialize an automobile in my path. Such high-impact, unpredictable and rare events are what author Nassim Nicholas Taleb calls “black swans.” Given enough time, no upward sloping trend line is immune from dramatic collapse.

A bike crash as a black swan is, in fact, an apt metaphor for what the investigative journalist and natural-born skeptic Barbara Ehrenreich believes happened to America as a result of the positive-thinking movement. In her engaging and tightly reasoned book Bright-Sided (Metropolitan Books, 2009), she shows how the positive-psychology movement was born in the halcyon days of the 1990s when the economy was soaring, housing prices were skyrocketing, and positive-thinking gurus were cashing in on the motivation business. Academic psychologists, armed with a veneer of scientific jargon, wanted in on the action.

The shallow bafflegab of such positive-thinking pioneers as Norman Vincent Peale (The Power of Positive Thinking, 1952) and Napoleon Hill (Think and Grow Rich, 1937) or the “prosperity gospel” preachings of such contemporary “pastorpreneurs” as Frederick “Reverend Ike” Eikerenkoetter, Robert H. Schuller and Joel Osteen are predictably data-light and anecdote-heavy. But one expects better of respected experimental psychologists such as Martin E. P. Seligman, who almost single-handedly launched the positive-psychology movement in academia that is, according to the Positive Psychology Center Web page (www.ppc.sas.upenn.edu), “the scientific study of the strengths and virtues that enable individuals and communities to thrive.” Ehrenreich systematically deconstructs—and then demolishes—what little science there is behind the positive-psychology movement and the allegedly salubrious effects of positive thinking. Evidence is thin. Statistical significance levels are narrow. What few robust findings there are often prove to be either nonreplicable or contradicted by later research. And correlations (between, say, happiness and health) are not causations. Seligman and his colleagues drank the positive-thinking Kool-Aid, Ehrenreich shows, but she provides the antidote.

Take Seligman’s “happiness equation” (physics envy lives!): H = S + C + V (Happiness = your Set range + the Circumstances of your life + the factors under your Voluntary control). As Ehrenreich notes, “if you’re going to add these things up you will have to have the same units [of measurement] for H (happy thoughts per day?) as for V, S, and C.” When she confronted Seligman with this problem in an interview, “his face twisted into a scowl, and he told me that I didn’t understand ‘beta weighting’ and should go home and Google it.” She did, “finding that ‘beta weights’ are the coefficients of the ‘predictors’ in a regression equation used to find statistical correlations between variables. But Seligman had presented his formula as an ordinary equation, like E = mc2, not as an oversimplified regression analysis, leaving himself open to literal-minded questions like: How do we know H is a simple sum of the variables, rather than some more complicated relationship, possibly involving ‘second order’ effects such as ... C times V?” We don’t know, thereby rendering the equation nothing more than a slogan gussied up in math.

Isn’t positive thinking better than negative thinking? All other things being equal, sure, but the alternative to being either an optimist or a pessimist is to be a realist. “Human intellectual progress, such as it has been, results from our long struggle to see things ‘as they are,’ or in the most universally comprehensible way, and not as projections of our own emotions,” Ehrenreich concludes. “What we call the Enlightenment and hold on to only tenuously, by our fingernails, is the slow-dawning understanding that the world is unfolding according to its own inner algorithms of cause and effect, probability and chance, without any regard for human feelings.”

Feelings matter, of course, but the first principle of skepticism is not to fool ourselves, and feelings—both positive and negative—too often trump reason. In the end, reality must take precedence over fantasy, regardless of how it makes us feel.