I study the psychology of bullies. Donald Trump is a bully.

President Trump has been described as a socially immature toddler and dishonest bully, yet he continues to be supported by a large segment of America. How can this contradiction be reconciled? Developmental science offers some insights into this apparent paradox.

As a psychologist studying bullying among youth, I find many parallels between Trump’s behaviors and our research findings. While a presidential candidate, Trump openly engaged in some typical bullying behaviors found among children and youth: name-calling and belittling of others. He targeted his Republican competitors (“little Marco”) as well as Democrats who criticized him (“crooked Hillary”). Although surveys indicate that people of all ages disapprove of bullying, his actions appeared to boost his popularity.

In a sense, this fits. Although bullies are never liked, they are popular in certain situations. Our research shows that bullies initially become “cool” during their first year in middle school. We think that this link between bullying and popularity is strengthened by the collective uncertainty associated with the transition to middle school. As youth are trying to acclimate to the new setting, many worry about their own social standing and ask: Where do I fit in? Who should I hang out with? When the future is uncertain, it is vital to know not only where one fits, but also who is in charge. Dominance hierarchies help group members find their places and form alliances, and bullying is among the most primitive ways to establish dominance.

At the time of the presidential election, insecurity about jobs and future finances were concerns of many Americans living in small towns and rural areas with few job opportunities. These were the places where Trump did well enough to win the election. One can speculate that by capitalizing on their social and economic uncertainties, Trump won the popularity contest despite often coming off as unlikable.

Our research on middle-schoolers also shows that the popularity of bullies wears off after the transition period. That is, after the first year in middle school, bullies’ popularity gradually decreases. According to the latest polls, Trump is still supported by most who voted for him — although some are changing their minds. The question is whether his popularity will hold when and whether voters begin to feel that their circumstances are more stable and less transitional.

Assuming that Trump knew how to capitalize on the uncertainties facing Americans to get elected, does that make him a strategic genius? His other behaviors cast doubt on such a conclusion — but they do fit the data on immature and aggressive children.

Trump is known for his tendency to deny his role in controversial events. He has denied, for example, asking FBI Director James B. Comey to drop the investigation of former national security adviser Michael Flynn; he has also denied ever having had dealings with Russian agents, and has angrily described probes into these matters as “a witch hunt.” While the nation is waiting to learn the truth about what Trump has or has not said and done, his stubborn denial reveals a lack of social reasoning typical of aggressive children.

Public accounts or explanations of negative events provide us with important insights about social-cognitive maturity. When a young child is questioned whether he ate the last cookie (even when there are crumbs on his lips), the immature response is: “I didn’t do it.” Children deny the act before they learn that it is socially beneficial to admit the wrongdoing but deny any negative intent. Teens tend to become even more skillful and elaborate on various mitigating circumstances, such as not turning in their homework due to illness or because they were helping an ailing grandmother. These accounts reduce the likelihood of punishment and facilitate forgiveness.

Not only does Trump flatly deny almost every accusation leveled against him, but he also claims no personal responsibility for problems. Instead he blames others, most recently the media and the White House staff. Refusal to accept personal responsibility and a tendency to blame others are indeed trademarks of aggressive children. In fact, our research shows that aggressive children are much quicker to infer hostile intent in ambiguous situations and lash out in revenge. Blaming others is a self-enhancing defense mechanism: It protects positive self-views.

In addition to protecting his ego, Trump also tries to enhance his self-worth. What makes him look childlike are his unsubstantiated claims about his popularity. Despite the verifiable evidence, he repeatedly refers to his unprecedented electoral college victory and the unmatched size of crowds at his inauguration.

Trump’s use of self-enhancement tactics also helps explain why he feels he has been treated worse and more unfairly than any other president in history. Despite their (short-lived) popularity, most bullies are hypersensitive to negative feedback — and ironically feel mistreated.

Revealingly, in his interview with his biographer Michael D’Antonio, Trump says he is the same person as he was in first grade. He may well also be very similar to the person he was in middle school: Indeed, there are many parallels between Trump’s behavior and the facts and findings of developmental science on social reasoning and behavior. But if the pattern holds, he won’t remain popular for very long.

Juvonen is a professor of developmental psychology at the University of California, Los Angeles, and an author of “Bullying in Schools: The Power of Bullies and the Plight of Victims.”