Science can’t tell us how to act but it can often tell us about the impact of our actions. When it comes to the repercussions of separating infants and children from their caregivers at the US-Mexico border, the science is clear.

Last June, when there were a spate of articles about the harm being wrought by the Trump Administration’s family separation policy, James Coan, a psychology professor at the University of Virginia and host of the science podcast ,“Circle of Willis, penned an op-ed in The Washington Post, where he naively suggested that if migrant children were “obviously mistreated physically” we wouldn’t stand for it.

Well, sporadic protests aside, we are standing for it. Long after his article, the separations continue.

Hardliners such as former White House Chief of Staff General John Kelly and former Attorney General Jeff Sessions reason that it was the parent’s choice to enter the country outside of proper entry channels that put these children in pens and peril. By their logic, the harm is not blood on our hands.

However, for those who are not convinced by such disingenuous finger-pointing, permit us to rehearse the half-century of solid research warning about the dangers of prying babies and toddlers away from mothers: the worst bruises from isolation are internal — deep in the psyche of the child. They are also large and long-lasting. And for those who support or shrug off the current policies, they should at least acknowledge that forced separation is as violent an action as physical abuse.

Lately there has been an outcry over the lack of toothbrushes and toothpaste for the caged children. But forget cavities. Without diminishing the horrendous conditions that Americans would never tolerate for their own children, there are much more serious dangers than poor dental hygiene. In an interview for Coan’s podcast, Columbia University professor of psychology Nim Tottenham stated, “When we think of the basic needs of a human, we often think about food, water, shelter, medical care. But when you’re talking about a developing human, you have to also add in the caregiver…”

In the early 1960s, the renowned British psychoanalyst John Bowlby developed an influential theory of attachment, and along with his collaborator James Robertson delineated the stages of distress responses that children go through as they cope with being torn away from their mothers. First, they explain, there is the protest phase in which the child cries and screams. Then comes despair, in which the child gives up hope of reunification and becomes withdrawn. If the separation continues, most children sink into a dangerous state of detachment. At this juncture, the child appears to have annihilated his need for his mother. Later, even when reunited with the family, he or she frequently becomes emotionally distant and develops a fundamental lack of trust in other people. Though some children are more resilient than others, that last state is the most difficult to reverse.

Research on infant–mother attachment has come a long way since Bowlby. Psychologists concur that in the first few months of life, close facial interaction with the mother or mother figure are essential in organizing the developing brain. The dance between caregiver and child is of such developmental importance that the prominent psychoanalyst D. W. Winnicott once proclaimed, “There is no such thing as an infant… without maternal care one would find no infant.”

One of the world’s leading researchers on infant mother interaction, Columbia University Clinical Professor Beatrice Beebe, observed, “There is damage to the mother–child bond even after they are reunited. In many cases, when a baby is brought together with his or her mother again, the baby will initially turn away refusing to acknowledge the mother… [It] is a long and bumpy road back to the point of normalcy and basic trust.”

Ethical concerns often override the need for controlled, prospective studies of the sequelae resulting from removal of children from their primary caregivers. Instead, today’s researchers often study the outcomes of institutional care (e.g. orphanages) on infants and young children who are subsequently adopted. In an imaging study of the long-term neural correlates of adverse rearing conditions of 12–14-year-old children who were internationally adopted at a median age of 12 months from institutional care, University of Minnesota researchers found that when compared to children of the same age who were brought up in their biological families, “this temporally discrete period of early deprivation is associated with persisting alterations in brain morphology even years after exposure,“ and that these “alterations are not completely ameliorated by subsequent environmental enrichment by early adolescence” (Hodel et al., 2015). Moreover, as Tottenham emphasizes: “At the level of the brain, we know that early caregiving trauma is associated with a hyperactivity of threat-related systems of the brain that go on to produce risks for major depression, anxiety and a whole host of other mental illnesses, including substance abuse, PTSD, conduct problems, and so on” (Circle of Willis, 10:47).

The nightmare of separation is also a traumatic blow to the parents. For most of us, having a child is like having a heart outside oneself. Though trivial by comparison to the separations at the border, one night many years ago, we were in a mall chatting away, and suddenly noticed that our three-year-old had wandered off. For 10 minutes that seemed to stretch 10 years we could not find him. Thinking back over three decades, Susan still shivers about it. “I was so panicked I thought I would die,” she recalls. Three decades and it’s as fresh as yesterday.

Though we have slavery, the Holocaust, and the separation of Native Americans from their families as historical parallels to today’s border separations, it is hard to crawl into the minds of parents enduring the unthinkable or into the minds of children enduring such trauma. But we should damn well try.