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Predictably Irrational

The latest rage in books seem to be those that point out how humans behave. Consider it pop psychology for the masses, and sometimes, of the masses.

Dan Ariely’s newest offering, Predictably Irrational: The Hidden Forces that Shape Our Decisions, is no different. Chapter after chapter, the author walks the reader through dozens of experiments conducted over the past few years that show basically the same pattern — time and time again, we humans behave irrationally. But predictably so. So predictably so, in fact, that entire companies and virtually all marketing is designed to take advantage of the ways we behave. Ariely refers to the field as “behavior economics” and himself as a behavioral economist.

As someone who lives and breathes psychology for a living, it’s always refreshing for someone to point out how we always behave in the same irrational ways. In each chapter, Ariely starts with the problem, describes the experiment used to illustrate the problem, and then discusses the results of that experiment (or set of experiments) that prove his point, explaining the “irrational” behavior. Ariely has an extremely likable and engaging writing style and you instantly fall into this quick and easy read.

For example, in one experiment, he showed how the cost of a pain pill was directly related to pain relief experienced by people taking the pill. A $2.50 pill relieved more pain, subjectively measured, as opposed to the $0.10 pill (even though both were the exact same pill). In a similar experiment, he showed how when people kept track of what types of medications they bought — generic or name-brand — the people who took the name-brand medications experienced more relief of their symptoms. Not because the generic is any less effective (by law, it has the same formulation as the name-brand medication), but because perceptions often affect how they experience something.

In another chapter, he illustrated how when a person expects to have a good time doing something, they do. When they expect to have a miserable, unhappy time, they more often than not live up to that negative expectation. As humans, we have a direct impact on our own experiences and expectations, sometimes more than we consciously realize.

Another chapter in Predictably Irrational, Ariely describes how marketers often work their magic in how they position their product strategy. When a company gives people more choices (rather than just one or two), they help manipulate the choice we, the unwitting consumer, will ultimately make.

Some of Ariely’s observations are not particularly surprising to me, but they might be to others who read this book. Some of his observations about human behavior I found downright simplistic, owing to the plain cause and effect attitude he takes toward his unpretentious undergraduate experiments. Psychologists have long used undergraduate experiments to build the initial foundation in their complex theories about human behavior. But then they move on to more complex and generalizable experiments.

Ariely, on the other hand, seems to have run his undergraduate experiments and then called it a day, suggesting they alone provide direct answers to human behavior. I think in this respect, Ariely is perhaps a little naive, as undergraduate experiments can usually be manipulated or designed (sometimes unintentionally) to “prove” something the experimenter was after, but not necessarily a universal constant in human behavior.

This may be a subtle distinction lost on many of Ariely’s readers. This book simply does not do justice to the complexities of either economic models and theories of human behavior, nor to those of psychology.

One of the downsides to Ariely’s writing is that he sometimes draws overly broad generalizations and conclusions from many of the experiments he cites (which often include him as a co-researcher). Conducting an experiment on a few hundred college students doesn’t always lead you to conclusions that apply to the general population as a whole (because college students are not representative of the population, especially in areas of decision-making which is greatly affected by age, wisdom and experience).

Another annoying aspect of the book is that Ariely often expends the vast majority of a chapter describing the behavior or problem, illustrating it with experimental data and such, and then abruptly ending the chapter. There’s very little, “… and here’s what you can do with this data,” or,”… and here’s how you can change your own life based upon these findings.” I guess it’s not intended as a pure “self-help” book, but when he does offer up some tiny pieces of self-help advice, they seem to be shallow observations, “Well, this is how I changed things in my life.” Or the more frustrating acknowledgment the author made in one chapter where, even knowing what he did, he couldn’t change his own behavior (e.g., insight is usually not enough to affect change).

At the end of the book, I was left scratching my head and thinking I knew more than I did before I read it. But I also wondered, would I be able to apply any of this new information and knowledge into not allowing myself to be so easily manipulated or to behave so obviously “irrational.”

I doubt it.

304 pages, hardcover

Predictably Irrational

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John M. Grohol, Psy.D.

Dr. John Grohol is the founder & CEO of Psych Central. He is an author, researcher and expert in mental health online, and has been writing about online behavior, mental health and psychology issues -- as well as the intersection of technology and human behavior -- since 1992. Dr. Grohol sits on the editorial board of the journal Computers in Human Behavior and is a founding board member and treasurer of the Society for Participatory Medicine. He writes regularly and extensively on mental health concerns, the intersection of technology and psychology, and advocating for greater acceptance of the importance and value of mental health in today's society. You can learn more about Dr. John Grohol here.

APA Reference
Grohol, J. (2016). Predictably Irrational. Psych Central. Retrieved on September 28, 2020, from
Scientifically Reviewed
Last updated: 17 May 2016
Last reviewed: By a member of our scientific advisory board on 17 May 2016
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