There were many reasons to oppose President Trump’s travel ban on refugees and visitors from seven predominantly Muslim countries, which is now blocked by a federal court’s temporary restraining order. Unfortunately, those same objections are also likely to apply to the revised version of the executive order that Mr. Trump promised on Thursday, which will share with its predecessor the goal of “immediately protecting the country” — presumably by keeping out people from countries he deems to be a threat.

One objection to such policies is that there is no good evidence that citizens of the countries the president has singled out so far present a significant threat to the United States. Another is that any policy that effectively discriminates against members of a specific religion is decidedly un-American.

But perhaps the most important objection, given the ostensible goal of protecting national security, is that these are precisely the sort of policies that can increase radicalization of Muslims already on American soil. Recently, a group of former diplomats and national security officials signed an open letter condemning the original ban on that ground, arguing that it would make the country less safe by feeding the narrative that America is anti-Islam.

Mr. Trump and his advisers should know that this is not mere speculation; it is grounded in social science. In a study published in 2015 in the journal Behavioral Science and Policy, we showed that policies like Mr. Trump’s ban may very well promote the psychological conditions that fuel the radicalization he seeks to combat.

We conducted a survey with nearly 200 American Muslims, half of whom were immigrants, half of whom were born in the United States. We asked them about their experiences as religious and cultural minorities, including their feelings of being discriminated against on the basis of their religion. We also asked how they managed their dual identities as Americans and Muslims, and how they felt toward fundamentalist Islamic groups and extremist causes.

Our findings were clear: The more our participants reported feeling culturally homeless — that is, fully belonging neither to American culture nor to that of another nation — and discriminated against on the basis of their religion, the more they said they experienced a lack of meaning in their lives. In turn, this loss of meaning was associated with greater support for fundamentalist groups and extremist causes.

This finding was consistent with research by the social psychologist Arie Kruglanski that showed that the psychological need for significance, not religion or ideology, is what propels people toward extremism. Extremist groups offer a sense of purpose, certainty and belonging to those who work on their behalf.

These groups go after Muslims who feel culturally homeless, leaning heavily on the claim that the West is anti-Islam. In this context, Mr. Trump’s original ban, which sent a strong message that Muslims were not welcome in this country and could not be “real” Americans, amounted to free propaganda for extremists. As one poster argued on a pro-Islamic State web channel, Abu Bakr al-Baghdadi, the declared leader of the Islamic State, should consider Mr. Trump’s executive order a “blessed ban.”

The good news from our study was that the overwhelming majority of our participants reported that they wanted to integrate aspects of American culture and their cultural heritage into their own identities. In addition, overall support for extremism was very low. A Trump administration that wants to build a more secure nation would look to integration, not alienation, as the goal for America’s Muslims.

The one welcome result of Mr. Trump’s ban was that it prompted non-Muslim activists to come out in force throughout the country — from Washington to Dallas to Los Angeles — to show solidarity with those affected. Rallying at airports and city centers, these protesters countered Mr. Trump’s Islamophobic language with the message that Muslims are welcome and an important part of America’s cultural fabric. It is precisely this kind of sentiment that we need to hear expressed by our leaders.

The exact nature of the revised version of the executive order, which Mr. Trump said he would issue soon, is unknown. In the meantime, the judicial and legislative branches of the government should take a look at the social science showing why Islamophobic policies pose a genuine threat to Americans of all cultural backgrounds and faiths.