Are Human Decisions Eminently Rational, Hopelessly Irrational, or Neither? By: Dr. Robert Cialdini


 the rational animal


There is an intellectual train speeding our way, carrying a revolutionary payload for those who want to truly understand how people make decisions. Douglas Kenrick and Vladas Griskevicius are at the center of this scientific revolution, and their new book The Rational Animal: How Evolution Made Us Smarter Than We Think, gives us the inside story, with some important implications for anyone seriously interested in understanding the psychology behind business choices…as well as personal ones. 

In the classic view of decision-making, our choices are highly rational and amazingly self-serving.  This is the “Rational (hu)Man” view of human nature, caricatured in the movie Wall Street (Remember Gordon Gecko’s dictum that “greed is good”?).  But over the last two decades, social psychologists and behavioral economists have uncovered countless ways in which people’s decisions are short-sighted, ill-informed, and otherwise shockingly biased.  Dan Ariely’s masterful Predictably Irrational is a prime example.  If you look up “list of cognitive biases” on Wikipedia, for instance, you will find over 100 mental “defects listed,” including loss aversion, the base rate fallacy, the clustering illusion, the decoy effect, the Barnum effect, the gambler’s fallacy, the false consensus effect, and dozens more.  This has led to a second view, one of human decision-makers as relentlessly and hopelessly irrational—though as Ariely points out, predictably so.

In their book, social psychologist Douglas Kenrick and marketing professor Vlad Griskevicius argue for a third view: People’s decisions are driven by a “deep rationality” – a set of evolved biases that would have helped our ancestors and their genes survive, and that continue to influence our choices in the modern world.  Honed by lessons our ancestors learned, our decisions today (even our seemingly silly ones) reflect a deep-seated evolutionary wisdom.

Kenrick was my first doctoral student at Arizona State University, and he and I have worked together for the last three decades.  Griskevicius was one of my last graduate students, who has gone on to a position as McKnight Associate Professor of Marketing and Psychology at the University of Minnesota’s Carlson School of Management. 

Their new book also proposes a second notable departure from the traditional Rational (hu)Man model: Rather than having a single Wall Street banker type inside our heads, we have several different types of decision makers.  Kenrick and Griskevicius refer to them as our “subselves” – evolved systems for dealing with different decisions in ways that vary according to the principal goal one has in mind at the time.  “Is blowing money on a conspicuous new car a waste or an investment?  Is giving money away a cost or a benefit?” Kenrick and Griskevicius ask.  “The answer,” they contend, “depends on whether one is focused on attracting a romantic partner, caring for a child, or trying to close a business deal.” 

This new perspective has important implications for understanding consumers’ many irrational biases. Although a “bias” is often viewed as a deficiency and equated with poor decision making, many of our modern-day biases stem from adaptive tendencies that were installed in us by a long and informative ancestral history of success and failure.  As the book’s authors point out: “We humans are born to be biased – but for good reason. Instead of being design flaws, many of our biases are actually design features. Understanding how these biases work will help marketers harness our evolutionary tendencies to better predict how consumers will behave.” Thus, by connecting modern behaviors to their ancestral roots, communicators are better able to understand and anticipate the seemingly irrational tendencies of modern-day “rational animals.”

 Bob Cialdini observes that “Douglas Kenrick and Vladas Griskevicius are at the center of this scientific revolution, and they deliver this valuable information to a broad audience in a smart and entertaining way. The Rational Animal offers us a new way to think about decision making.   I consider it a must-read—and best I can tell when I look inside myself—not because of my association with its authors but because of the importance of its insights.

 For a 3 minute video in which Kenrick and Griskevicius summarize their central points, go to:The Rational Animal: How Evolution Made Us Smarter Than We Think.  

  • Steven Feinberg

    Will read…what bias led me to that instant decision?

    Steven F

  • Anthony McLean

    Decision making and our approach to it is as critical a skill as being able to influence people. As a CMCT and someone who has been required to make critical decisions in life and death situations and then asked to explain them in courts of law, I can attest to the real world requirement of a deeper understanding of how we make decisions. Thanks for the recommendation – I have already ordered my copy!

  • Tony Pies

    It seems I will wait for a lot more reviews before I buy.

  • Debra Little

    “The answer,” they contend, “depends on whether one is focused on
    attracting a romantic partner, caring for a child, or trying to close a
    business deal.”
    This ‘answer’ seems to present a very narrow, limited realm of personal motivations. Where is the heart of compassion for ‘other’, for effecting change for the greater good? For spiritual fulfillment or simply considering how our actions effect others in & around us & future? These reach much further ~

Subscribe to the
Submit your email below:

vPOP Live & Online

From you’re the comfort of your home or office, explore the psychology behind what drives us as humans and teaches us how to ethically move others in our direction. Click here to register now.

Share Your Thoughts

Help us help others by leaving your comments, insights, and reviews on This demonstration of “social proof” will benefit all.
Click below to read and leave current reviews on for:

Dr. Robert Cialdini’s Books

Twitter Updates