If a baby is ignored -- even for a few minutes -- he won't remember it later, will he? That's the question Canadian researchers asked, and the answer may come as a surprise.

Psychologists at the University of Toronto Scarborough performed an unusual experiment to test the effects of "emotional deprivation" on six-month-old babies.

They asked parents of 30 babies to briefly ignore their six-month-old infants. The babies' mothers were asked to face the infant, who was seated in a car seat placed on a table. The mother was instructed to look at a spot slightly above the infant's head and maintain a neutral facial expression for two minutes, not smiling or cooing with their babies as they usually would.

They then played with them for two minutes, then ignored them again for two minutes, before playing with them again.

Next, the researchers took saliva samples from the babies to measure their hormone levels. They found that the emotional response in the infants was immediate, with the tests revealing elevated levels of the stress hormone cortisol.

To see whether the babies would remember the episode, the infants were brought back to the same experiment room 24 hours later, with the same researchers taking their saliva samples.

Although this time, the parents didn't ignore their babies, the infants demonstrated a distinct "anticipatory stress response" anyway, showing a marked elevation in cortisol.

That suggests that the babies were able to anticipate stress based on the expectations formed from the previous day about how their parents would treat them.

Another group of infants who were part of the two-day experiment, who acted as controls and weren't subjected to the parental-non-responsiveness, showed no changes in their cortisol on either day.

But the researchers also found that overall, the levels of stress hormones were lower on the second day compared to the first day, suggesting the babies were able to adapt to the stressor, a finding that the research team found interesting.

"The capacity to adapt to changes in parenting may be an evolutionary advantage that contributes to the reciprocal nature of the parent-infant relationship in humans," suggested the study's lead investigator Dr. David Haley, in a news release.

The results of the study are published in The Royal Society journal Biology Letters.

Experts say the findings are in line with what is already known about "attachment theory," the theory that children need a close relationship with at least one primary caregiver in order to develop normally.

Clyde Hertzman, director of the Human Early Learning Partnership (HELP) at the University of British Columbia, says the research helps explain the biological basis of bonding and attachment. He says it shows that children as young as six months have the capacity to remember stressful events in "intimate contexts."

"Most important, it helps us to understand why social and emotional deprivation in the first year of life can have profound long-term impacts on child development and mental health," Hertzman said in the news release.

Dr. Haley said researchers are only beginning to understand the mechanisms that allow babies to anticipate, remember, and adapt to unusual emotional events in an attachment context.

What remains unknown is whether the memories that trigger the anticipatory stress response are located in the mind or the body.

"It isn't clear where or how the information is being retained," said Megan Gunnar, professor of psychology of the Institute of Child Development at the University of Minnesota.

Rather than suggesting that "the child can 'think' about yesterday," she said, "I might shift more to the wisdom of the body (the child's stress system retains the experience)."