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Do Sales Personality Tests Actually Predict Anything?

Liston Witherill
Liston Witherill
12 min read

Personality tests are a multi-billion-dollar industry because they promise to teach us more about ourselves and others – but do they work, and in what situations? In this episode, we’ll uncover the accuracy and usefulness of personality tests so you know how they can (and can’t) be helpful.

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Do Sales Personality Tests Actually Predict Anything?:

Full Transcript

How Sales Personality Tests Started

During World War II, an American mother-daughter combo hatched a plan. They were devoted followers of psychologist, Carl Jung, and began wondering if Jung’s research could be applied systematically to learn more about people.

You see, they noticed people in their household had really different personalities. It was during World War II, and many women began to enter the workforce. Prior to the war, most women just planned to be housewives, but the war changed all that.

So what would these women do for work? Well, this mother-daughter combo thought they could create an assessment that would help women determine which jobs they’d be best suited for given their innate personalities.

You’ve probably heard of this mother-daughter combo, Myers and Briggs, creators of the Myers-Briggs type indicator assessment. But does it work? How accurate is it and what can we even do with the information it gives us?

What the Evidence Says About Personality Tests

Before we get into the hard evidence, it’s worth noting that personality testing is a huge industry. The most popular test, Myers-Briggs (MBTI), is taken by 2 million people every year, and the whole personality testing industry, it’s estimated at $2 billion annually.

That is a lot of dollars. 90% of Fortune 100 companies use one or more personality tests in their hiring, training or talent development practices, which is all to say, there’s a lot at stake in the study of personality tests, there’s a lot of conflicting information out there, because whole careers, companies and professions are built on the backbone of these darn tests. That’s why I find it so difficult to sort through all of the different conflicting information.

Now, I also want to note there are a lot of different personality tests, but I’m only focused on three in this particular episode to limit the scope: MBTI, DISC and The Big Five. These are the most popular by far, and the research on them pretty well documented as well. So what does the evidence say about MBTI and DISC? Well, let’s start with what MBTI attempts to measure. It starts with this assumption, that there are real differences between people. You know it and I know it, we’re born with different personalities. These aren’t character flaws, they’re simply differences to be understood and navigated. To that I say yes. So far so good, and you probably agree.

But let’s turn immediately to Annie Murphy Paul, author of The Cult of Personality Testing. Here’s a quote from her book. And I quote,

“There is scant evidence that MBTI results are useful in determining managerial effectiveness, helping to build teams, providing career counseling, enhancing insight into self or others, or any other of the myriad uses for which it is promoted.”

I think you can see Annie Murphy Paul is pretty down on MBTI. I want to focus, for the purpose of this podcast, on three things she said there: managerial effectiveness, helping to build teams, AKA hiring, and enhancing insight into self or others, which is to say being a more effective communicator.

There are some research papers that show correlations between job performance and personality. But there is a problem with that. Here’s a quote from The Journal of Applied Psychology,

“The problem with personality tests is that the validity of personality measures as predictors of job performance is often disappointingly low. The argument for using personality tests to predict performance does not strike me as convincing.”

So on the one hand and he says, absolutely no evidence, whatsoever, that there’s any correlation between MBTI results and all the stuff we care about: managerial effectiveness, building teams, providing career counseling, enhancing insight into self or others. On the other hand, there are some studies that show some correlation between MBTI results and job performance, but that correlation is “disappointingly low” to the point of personality tests not having any predictive power at all. But what about the use case I talked about at the start of the show? Does knowing your personality type or someone else’s make you a better communicator? Well, anecdotally, a lot of people say yes.

If you go look up some online tools, which I will not name here, you can check out tools built on MBTI or DISC or lots of other personality tests, and there’s a lot of people who will give testimonials saying that the results of the personality test and understanding personality types have helped them become more effective communicators. I will interject here. I’ve taken the DISC assessment a lot of times, I’ve taken Gallup StrengthsFinder, I’ve taken MBTI several times, and I can tell you, not only did I feel like I understood myself a little bit better, but I also understood where I was communicating effectively and ineffectively with different types of people, or at least I felt I did.

Now, we’re driven to make sense of the world, and we’re driven to find meaning, and we’re driven to understand, and that’s certainly true of me. I will tell you that my enhanced understanding, it feels very real. I really do feel like it made a difference. But what I can’t find is any evidence of this. So if you have valid research studies proving that taking a personality test or understanding others or getting trained on personality types makes you a more effective communicator, send it to me. I want to see the valid research. I have poured through it, I have found absolutely nothing, including by the companies who directly get paid for these personality tests. So, for now, the answer is there is no evidence that understanding your personality profile or someone else’s will make you a better communicator.

I think this brings us to the point of looking at just a few of the problems with personality tests. There are many, but the first is that people lie on the test. Now, you can imagine if you’re going in to apply for a job for a sales role or you’re giving a test or you’re on the hiring side and people are coming to you for a job, there’s a lot of incentive to answer on that test the way you think the person evaluating the test will want you to answer. Just no further than sales stereotypes. Many of us think that outgoing people do better in sales. That’s actually not the case. I’ll get to that a little bit later. But a lot of people will have an incentive to answer in ways that make themselves seem more outgoing.

Some people will also lie on the test for aspirational reasons. They’ll answer the questions based on the way they want to see themselves rather than how they actually are, which brings us to the next problem, these tests are self-reported. Rather than observing someone’s behavior over a long period of time in a big variety of situations, which is obviously impossible, what we’re left with are self reported tests. And we know, people exaggerate, people lie, sometimes people just plain lack self awareness so they don’t do a good job on these tests, which brings us to point number three. The tests aren’t repeatable enough to be considered valid. People will answer differently, depending on time and context.

Now, I can tell you I’ve taken MBTI three times, and I’ve had three separate results. ENTJ, ENTP and ENFP. If you look at all of the different possibilities within MBTI, there’s 16 different personality types. I’ve just covered three out of 16, but when I read all of them on a single graph, I can tell you I feel like I pretty closely match up with the bottom half, eight out of 16, which is a problem. I’m not obviously one. Same problem with my DISC results, they varied over time. One time I was a DI, one time I was a strong D, one time I was a DC. It’s worth noting also that C and I are polar opposites.

So, repeatability is a big problem. One of the issues that I see there is MBTI is bi-modal, meaning they’re just this or that questions, they’re not on a spectrum and they’re not on a rating system, often called a Likert scale, and DISC asks you to answer what you feel most strongly about and least strongly about, which again is more or less bi-modal. What we know about personality is most people fit into a normal distribution. So if you plot out the whole society, it’s going to look more like a bell curve than buckets, the way that these tests are set up. So that is an inherent flaw in the way the tests are created.

Now, we also know that people behave differently in different situations. I won’t get into it too much, but maybe you remember the Stanford prison experiment which showed behavior can be contextual. So when college students were given prison uniforms and said they were in charge of prisoners, they behaved totally differently than they did in their normal everyday lives. If their friends saw them on video acting as prison guards, they would be absolutely shocked at their behavior. So we know, even though that’s an extreme example, that behavior is contextual.

There’s another problem that I don’t like about these personality tests that came up in my own experience and that is, they can be used to discriminate. There’s an in-group and out-group dynamic that can emerge. I was in a company, we did a DISC personality assessment. A consultant came in, had everybody take it, they plotted everybody’s personalities on a big chart, and we got to see where most people in the company lied on the DISC personality chart and they were grouped pretty closely together, mostly, which again, there are problems with accuracy and repeatability. But overall, it showed that certain types of people were more likely to be attracted to this job.

There were two problems with that. One is, some people passed judgment on others as ineffective after the test results were in and each employee was plotted on the graph, and that really bothered me. It struck me as horribly unfair, because we weren’t told this person or that person is more effective or less effective, we weren’t told… Essentially, the second problem, what to do with the results. So what? I was this or I was that personality, what should I do about it? Who cares? But here’s the thing. If you’ve been around enough other people, you know that there are some really big differences between us. We may not use the language of MBTI or DISC, we’re more likely to say things like, “She gets along with everyone,” or, “He’s a loner,” or, “She’s a big picture thinker,” or, “He’s obsessive about details.” There are real differences. Let’s assume that to be true for a second.

We know MBTI isn’t great at uncovering them, but differences do exist. So is there something else that does a better job? Enter The Big Five personality traits. So here’s what the research says about The Big Five. First of all, you’re probably wondering Big Five what? Well, here are the personality traits in The Big Five. Openness to new experience, conscientiousness, extroversion, agreeableness, and neuroticism. There’s also a suggestion that a sixth trait should be added, which is humility, honesty.

A lot of the research shows a lot stronger correlation in Big Five to job performance and communication. So in one HBR, Harvard Business Review article, the author interviewed over 1,000 salespeople. The study is especially relevant to our purposes here because only high tech and business services salespeople were studied as part of the author’s workshops. What he did is he gave all of these people personality tests, and he knew what their job performance was and he plotted that along with their personalities. He claims to have identified seven personality traits that indicate success in sales: modesty, conscientiousness, achievement orientation, curiosity, lack of gregariousness, lack of discouragement, and lack of self consciousness.

Now, what we don’t know is how much is enough modesty to be successful? Or, can I just be modest but not having achievement orientation? Are five out of seven enough? And how much of those five do I need? What if I’m off the charts in one and the opposite in another? We don’t know. We don’t know from the study, I don’t know that the author knows, which means there’s limited usefulness in this for hiring, and there’s somewhat limited usefulness in this for your own communication purposes because there’s so many dimensions here, it’s hard to tell what should you do. But it does seem to be stronger than the evidence that I’ve presented so far for MBTI and DISC, which is to say none. This seems to be a lot stronger.

In another study of The Big Five personality traits, they looked at job performance for financial managers. What they found is those who did better typically scored highly in conscientiousness and low in neuroticism. This typically translated to better customer service. Pretty easy. Right? Now note two things there. One is, we didn’t look at seven personality traits, we looked at just two out of The Big Five, and it was multidimensional. When they did this study, they couldn’t find one single personality trait that was more likely to link to success, they found two. But even then, the correlation wasn’t super strong, it wasn’t like 0.9, it was something like 0.25.

So while it did show some more promise than other studies I’ve seen, probably not enough to base your hiring decisions on, and probably not enough to start doing the hard work of starting to change your personality, if that’s even possible. But what we do know is that The Big Five has been shown to correlate strongly to political affiliation. Those higher in conscientiousness tend to identify as politically conservative while those higher in openness to experience tend to identify as politically liberal. So there is strong evidence of The Big Five being predictive of real world behavior and decisions. But the original question was one of adaptability. Can we become better communicators if we just know someone else’s preferred style of communication?

Now, we’ve arrived at an internal conflict here. If, in fact, we have set personalities that can be revealed through testing, then we can’t much adapt ourselves permanently to a career or a situation. So, how set and deterministic is personality? Well, in one study, psychology students were given personality assessments, and then they were given communication skills training over two different courses, one beginner and one advanced, to see if their personalities had any impact on their ability to improve communication skills. The result, and I quote, “Participants showed substantial progress in their mastery of the communication skills after both courses. Surprisingly, none of the personality factors predicted the level of mastery of these skills.” So, perhaps there’s no such thing as a natural communicator, and certainly, there was no indication that the personality assigned to you based on your test results had any bearing on your ability to improve in your communication.

So I’ve talked about a lot of stuff here, and I know this is a very research-heavy episode. I’m glad you hung with me and got to this point. I end every episode with key takeaways and action items, so I’m going to do that now just to summarize the whole thing for you. Personality tests are full of problems, and they have the look of junk science. Yes, there are differences between people, our personalities and how we behave, but we fall on a spectrum, and we can’t much be pinpointed to have a single personality type that explains all of our behavior. It’s just not that way. There’s a lot more research that needs to be done before we can draw conclusions about who or what is most effective, and there’s just not any evidence that knowing someone else’s personality type or having training in personality styles is going to make you a more effective communicator.

There is evidence though that communication training itself can make you a more effective communicator, whatever your personality style. Now I’m interjecting my own opinion. It stands to reason that the more self aware and situationally aware you are, the more you’ll be able to adjust on the fly, be more adaptive and be a better communicator. Since I always end this podcast with actionable items, here’s what I have for you today. If you want to become a better communicator, focus on improving your communication skills, not on understanding personality. If you’re not incredibly interested in the subject, don’t take any action, you’re off the hook. There isn’t any good evidence that understanding personality differences will make an impact on your ability to sell.

If you are interested in learning more about personality, check out The Big Five Personality Traits, it has, by far, the best track record and most credible research, although it does have its own problems. That’s it for this episode of Modern Sales. That was my take on personality tests and their usefulness in sales. In next week’s episode, I’ll be asking the question, is it pain or is it gain that makes us buy things? And I’ll be looking at Bose headphones versus Beats headphones. Yes, this is going to be a dog fight. If you aren’t already subscribed to this podcast, please do so by clicking the subscribe button. If you like what you heard, go to iTunes, leave a five star review, leave a six star review, leave a 10 star review. I would love that. It really helps me get the word out and other people to hear this podcast.

You can also get notified of all podcast episodes and get my free Daily Sales Insights newsletter. It has a custom hand drawing, you’ll sign up for the insights and you’ll stick around for the drawings, I promise. All you have to do is go to Again, that’s It’s totally free, and it’s linked in the show notes if you’re not sure how to get there. I also want to thank everyone who makes this podcast possible. Juan Perez is our editor, Mary Ann Nocum is our show assistant, our show theme and add music is produced by me, Liston Witherill, and show music is by Logan Nicholson at Music for Makers. Thanks so much for listening, I’m Liston Witherill of Serve Don’t Sell, and I hope you have a fantastic day.

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