In what has got to be the saddest-sounding experiment I've heard about in a long time, psychologists at the University of Tocredit: bbaunach/Flickrronto Scarborough have determined that very young babies remember when they've been emotionally deprived - even if that neglect lasts only a few minutes.

The experiment involved thirty 6-month-old babies being deliberately ignored by their parents. The mother of each baby was told to face her child, who was strapped into a car seat on a table in front of her, and completely disregard any cries for attention. The mothers were instructed to gaze somewhere just above their baby's heads and to avoid eye contact when the crying started. In addition, they were told to maintain neutral facial expressions and refrain from cooing, smiling or otherwise trying to comfort their crying babies.

After two minutes of this, the mothers were allowed to play with their babies for two minutes. Then the experiment was repeated one more time.

After the ignoring and playing phases, the researchers took saliva samples from the babies and tested their hormone levels. What they found was that the experience increased the levels of the stress hormone cortisol in the babies. While the fact that a baby would get stressed when being ignored by mom isn't all that surprising, what happened next is.

Twenty-four hours later, the babies were returned to the testing facilities to have their saliva tested again by the same researchers. Despite the fact that the experiment was not repeated and they were not subjected to neglect, their cortisol levels were again elevated. This, say the researchers, demonstrates an "anticipatory stress response." In other words, believing that they were about to be treated badly again, the babies became stressed.

The researchers say the levels of cortisol, while still higher than normal, were lower on the second day than on the first. This indicates that the babies were already adapting and learning to cope with the stress of being neglected. And according to Clyde Hertzman, director of the Human Early Learning Partnership (HELP) at the University of British Columbia, these findings help explain the biological basis of bonding and attachment.

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."

While the researchers say they can't determine if the memories that triggered the stress response were retained in the mind or the body, the bottom line is that they were retained. And this finding, it would seem, is bound to add some weight to the argument against letting babies cry it out as a method of sleep training.