My passion is single life, and that’s what I most enjoy writing about, but every once in a while, my old interest in the psychology of lying sneaks back into my life. That happened recently, when I saw that reporters at the Washington Post had been keeping a tally of all of Donald Trump’s falsehoods, misleading claims, and flip-flops since becoming president.

I had studied the lies of ordinary people years ago. I learned from that research how often people lied, and what kinds of lies they told. I wondered how Trump’s ways of would compare to what my colleagues and I (along with other researchers) had already documented. So I coded the most recent 400 of Trump’s lies using the same categories my colleagues and I used when we coded the lies in our research.

I wrote about what I found for the Washington Post. The article generated a lot of interest. It was the most popular article at the Post for a while, and it got picked up by other newspapers and websites in the U.S. and elsewhere. It also attracted 2,000 comments in the first day. That made me think that Psychology Today readers may be interested in hearing more about this, as well as some other observations about Trump’s lying that I did not include in my article.

The two most important categories of lies in the studies my colleagues and I conducted were self-serving lies and kind lies. Self-serving lies help liars get what they want and avoid what they don’t want, they help liars look better or feel better, or they spare liars from blame or or anything else they don’t want to experience. Kind lies are the same, only they are told for someone else’s benefit. When people lie to help you get what you want, or make you look or feel better, or protect you from something you don’t want, they are telling you a kind lie. (You can find some examples of the different kinds of lies in my article.)

Originally, I planned to code Trump’s lies into just those two categories. In my previous studies, I found that people tell about twice as many self-serving lies as kind lies. I thought that Trump would tell an even greater proportion of self-serving lies than the people I had studied previously, and that would be the big finding I would get to report.

I was right about Trump telling an especially big proportion of self-serving lies. Instead of telling twice as many self-serving lies as kind lies, he told 6.6 times as many. (His overall rate of lying was higher, too, as I discussed in the article.)

As it turned out, though, that was not the most interesting finding. As I read through Trump’s lies in the process of categorizing them, I realized I could not limit myself just to the categories of self-serving and kind lies. I had to add the category of cruel lies — lies that hurt or disparage or embarrass or belittle other people. In the research my colleagues and I did, we found that only 1 or 2 percent of all lies were cruel. That’s why I wasn’t going to bother with them when coding Trump’s lies.

Trump’s ways of lying also differed from the previous people I had studied in another way. His lies often served several purposes simultaneously (for example, sometimes they were both self-serving and cruel). In my previous research, it was easy to sort each lie into just one category. (I mention that because it is interesting, and also because it means that, for Trump, the percentages in each category will add up to more than 100 percent.)

Now let me tell you what I found when I tallied Trump’s cruel lies. Instead of adding up to 1 or 2 percent, as in my previous research, they accounted for 50 percent. When I first saw that number appear on my screen, I gasped. I knew, of course, that Trump likes to mock and denigrate other people (and countries and agencies), but I didn’t realize just how often he was doing that with his lies.

When I first thought about measuring Trump’s lies against what my colleagues and I had learned in our previous research, I thought I would look at other psychological processes involved in lying, too. For example, Kathy Bell and I did a series of studies in which we looked at what people did when they were asked about their opinion, but telling the truth about it would hurt another person’s feelings.

In those studies, participants were brought into a lab room set up as an art gallery, one at a time. They were asked to choose their favorite and least favorite paintings, and write out what they liked and disliked about each one. Only then were they introduced to an art student who, in the key moment of the study, pointed to the participant’s least favorite painting and said something like, “That’s one of my paintings. What do you think of it?” The participants were also asked about a painting of the artist’s that they did like, as well as paintings by another artist they never met.

Participants in the most difficult situation — talking about a painting they hated with the artist who painted it — almost never told the simple truth: “I hated it.” Instead, they tried to say things they could defend as truthful, even though what they said was deliberately misleading. For example, they amassed misleading evidence: they often mentioned things they really did like about the painting, while not mentioning as many of the things that they disliked. By describing more aspects that they liked than aspects they disliked, they might give the artist the impression that they liked her painting. Her feelings would not be hurt. And the participants would get to tell themselves (and anyone who challenged them) that, hey, they told the truth — they really did like those things they said they liked.

The participants came up with other interesting strategies, too. For example, they sometimes exaggerated how much they disliked the other artist’s work, so that what they said about the work of the artist right there with them would seem more positive in comparison.

Are you starting to realize why I never did similar analyses of Trump’s lies? First, the studies Kathy Bell and I did were of kind lies, told to spare the feelings of the artists in our studies. But only about 10 percent of Trump’s lies were kind lies (compared to about 25 percent in my previous studies of lying in everyday life).

More importantly, Trump does not seem to care whether he can defend his lies as truthful. Although I cannot know this for sure, he does not appear to feel embarrassment or shame about lying. He doesn’t seem to be thinking about how he can lie in ways that can be defended as truthful, as the participants in my previous studies had done. He seems to just state his lies starkly, and move on.

In the future, we will know much more about the psychology of Trump’s lies. In the brief time since my article was published, several researchers have already contacted me saying that they have studies in progress or articles that have been written but are not yet published.

I originally thought I would title this article, “How Trump Blew Up the Science of Lying,” but that is not quite accurate. Trump has not so much defied science as he has nudged social scientists to think in new or more complex or creative ways about how and why people lie.