Book review: Personality: What makes you the way you are

Personality: What makes you the way you are, by Daniel Nettle.
Oxford: Oxford University Press, 2007

I have to confess that I’ve felt an irrational attachment to the Myers-Briggs personality typology at the expense of other perfectly good systems, in particular the Big Five system that currently dominates research. This book remedied that, however, providing a fascinating grounding in the Big Five traits in terms of related brain areas or functions and genes.

Nettle begins with an overview of how the Big Five were determined (as clusters of correlated traits that emerged from studies of various aspects of personality) and how different behavioral patterns and personality traits might have evolved. Of particular interest is the question of why people have varying characteristics—in other words, why have different types persisted in the human population? why aren’t we all roughly the same? In a nutshell, the answer is that there is no single optimum personality that it is always advantageous to have.

One reason for this is that the environment changes and demands different things from different generations (interestingly, the environment includes other humans and their traits). Thus, the pressure of selection is usually not going to zero in on a particular level of any given trait or behavioral tendency and eliminate other levels from the mix. Nettle describes some studies of guppies, which showed that cautious behavior is linked to the presence or absence of predators in the environment, and there appears to be a heritable component to this behavior. Also, if naturally cautious guppies are placed in a predator-free environment, the level of cautiousness in the population drops after several generations, suggesting that there is survival value in both being wary and being relaxed, depending on environment. And there’s a continuum of wariness levels in a single species, rather than two species with different characteristics, because the populations mix and also because the level of predation in a particular environment can fluctuate. Nettle’s summary seemed to me to hint at some deep thoughts about diversity and individuality:

“No specific level of wariness is globally favored by selection, though for every individual guppy there is a level of wariness that it would be best to have.”

The heart of the book is five chapters that investigate each trait in turn: Extraversion, Neuroticism, Conscientiousness, Agreeableness, and Openness to experience. Each is explained in terms of the brain mechanism or function that it expresses. Those high in Extraversion, for example, are particularly attracted to the evolutionary carrots that offer rewards, whereas Neurotics are more attuned toward the sticks that warn of danger; Extraversion is associated with happy moods and Neuroticism with negative feelings. Conscientiousness has to do with self-control, and Agreeableness with the desire for harmony with others. Openness to experience is associated with the propensity to make broader associations of meaning (i.e., being more likely to see or create connections between relatively disparate objects or concepts).

Each chapter explains what we know so far about the trait in terms of both behavior and its neural and/or genetic underpinnings, with a good number of references to papers describing current research. For some traits, we know more about the related brain structures than for others, and of course it’s impossible to list all the possible connections. I was hoping to see something about the temporal lobes and Openness, but maybe there’s not enough research on that yet to make it worth mentioning, or maybe there just wasn’t room.

In the case of every one of the Big Five traits, a single optimum level of the trait has not become dominant in humankind; i.e., there’s a considerable range of levels of Extraversion, etc. This suggests that the optimum level varies with the environment, which of course varies in time, sometimes favoring the bold and sometimes the cautious, for example, so that neither end of the spectrum is bred out of the population. Nettle’s descriptions of the pros and cons of each trait were for me some of the most interesting material in the book.

Conscientiousness might sound like a universally desirable capacity, for example, and the more the better. However, high levels of Conscientiousness can lead to rigidity and missed opportunities, and low levels can be advantageous in changeable situations where behavior needs to be fluid and responsive. The dangers of being disagreeable are fairly obvious, but being too agreeable and always putting others before yourself is not good either. Neuroticism certainly seems like the least desirable of the Big Five traits (alas, I scored high on that one), but even there, the capacity for caution and reflection can be useful, and a dissatisfaction with what is can spur you to achieve more.

Throughout, Nettle recommends that you not bemoan your level of any particular trait, but instead focus on its advantages and try to arrange your life so that you can use your strengths and protect yourself in areas where you’re weak. (To go back to that guppy quote, basically we have to find the place where the mix of traits we’ve inherited is most useful.) This may sound obvious, but it can take a long time to get a clear picture of your true strengths and weaknesses, separate from what you wish were so and what those around you are like or wish you were like. It’s only been in my late 30s and into my 40s that I feel like I’ve started to truly understand why some things are hard for me and why I’m drawn to other things, and to stop beating myself up for not being like more extraverted or ambitious people and try to structure my life so that I can function at my best.

The last chapter of the book focuses on how much you can change your life, given that your personality as measured by the Big Five traits remains fairly constant over the lifespan. There are small shifts, on average: “As adulthood progresses, people become slightly higher in Agreeableness and Conscientiousness, and slightly lower in Extraversion, Openness, and Neuroticism,” reflecting a shift from agency (the drive toward achieving things and expressing yourself) to communion (relating with others). But by and large, as the song says, what you’re born with is what you get.

However, Nettle did a really good job of presenting the flexibility of self-concept that’s possible within the relatively unchanging framework of predispositions that we’re born with, which I found both inspiring and comforting. For example, a personality trait can be manifested in a fairly wide range of ways: “…if your personality is causing you trouble and worry, you need to find alternative, and less destructive, outlets for the same characteristics. You don’t have to change yourself. You just have to change your self’s outlet.” Another option for changing your life is to change the story you tell about it, reframing events and characteristic behaviors in a different light.

By the end of the book, you’ll probably have a pretty good idea where you stand on each of the Big Five, but each of the five is divided into various subtraits, and if you’d like a more detailed look at how you score on some of those, you can take an online test. If you read the book or take the test, I hope you have fun exploring the range of human personality and where you fit in. As they say, it takes all kinds.


  1. Very interesting. Like you, I couldn’t help but see how this relates to me.

    One line you quoted was, “…if your personality is causing you trouble and worry, you need to find alternative, and less destructive, outlets for the same characteristics.”

    I used to have an OCD thing that drove me nuts. I would make up funny names — endlessly. My mind just fell into it, over and over, and I couldn’t stop. Recently, I wrote a novel and started on a second one. Since I began writing, I haven’t had one instance of making up names. In other words, I took a useless form of creativity that was driving me nuts, and redirected it into writing. Problem solved.

    Thanks for writing this up.

  2. I took the test. “Your level of intellect is low…Your level of liberalism is high.” Isn’t that a non sequitor? Just kidding. My test results were (moderately) not surprising. It’s interesting to ponder how I became so concrete and pragmatic, though. Oh wait, if I’m pondering my concreteness, isn’t that philosophical after all? Fun topic.

  3. I suspect one’s traits change quite a bit over time, yes? I was noticing how my answers to questions on that test were different than they might have been only a short time ago. So many factors affect who we are at a given moment. (I notice you’re reading _The Power of Place_, which is now squarely on my reading list.)

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