"Our findings are consistent with Freud’s notions of suppression and repression, but go a long ways towards demystifying the process," says the paper’s co-author Michael Anderson, an assistant professor of psychology at the University of Oregon. "Our work allows Freud’s idea to be understood in terms of widely accepted mechanisms of cognitive control that apply in a broader range of circumstances."

Using rigorous laboratory techniques, Anderson’s work shows that trying to keep an unwanted memory out of consciousness makes it harder for a person to recall that memory later on when he or she wants to recall it. The amount of forgetting increases with the number of attempts to exclude the unwanted memory from awareness, showing that the effects of inhibitory control accumulate with practice.

"Amazingly, this type of forgetting is more likely to occur when people are continuously confronted with reminders to the very memory they are trying to avoid. This is quite contrary to intuition, which says that seeing reminders a lot ought to make your memory better," Anderson says. " Under these circumstances–when reminders are inescapable–people must learn to adapt their internal thought patterns whenever they confront the reminder if they are to have any hope of avoiding the unwanted memory."

An everyday example illustrates this mechanism at work.

After having an argument with a friend, a person may wish to–or need to–continue interacting with the friend, even though the bad memory is brought to mind each time the friend or other reminders of the incident (for example, the place where the fight took place) are seen. If future interactions are to remain pleasant or functional, the powerful association set off by these reminders must be set aside.

"A more extreme example may be cases of abuse in which a child may be forced to live with an abusing caregiver and interact normally, without continuously thinking about the unwanted memory," Anderson explains.

There is a wide gap between the current findings and real-life clinical cases of traumatic amnesia, he notes. In his research program, investigators use simple pairs of words that are not emotionally significant to test subjects, and test subjects’ memories after a brief delay. Amnesia associated with trauma involves much more distinctive, emotionally significant experiences that could stem from very different mental functions.

"A great deal of further basic science remains to be done before we can know for sure whether these mechanisms might explain some instances of traumatic amnesia," he says.

However, the research provides a promising start by showing that avoiding a memory can actually make a person forget it. The research also points in some interesting applied directions.

"To the extent that this paradigm provides a clear way of studying inhibition, it might be used as a measure of the effectiveness of attentional control in various populations that are of great concern for both medical and social or humanitarian reasons," he says.

For instance, many current theorists have suggested the increase in distractibility and decrease in memory that is often associated with advancing age might be understood as a decline in executive inhibition processes. Schizophrenia also has been attributed to inhibitory deficits. Understanding the mechanisms that may contribute to these conditions could lead to better treatments.

Another application might be in helping people who are undergoing withdrawal from drugs to control intrusive thoughts about or cravings for their addicting substance.

"The new paradigm developed in this work draws a direct link between people’s efforts to regulate awareness–a fundamentally unobservable subjective experience–with an objectively measured behavioral consequence of that internal act: forgetting. They thus provide a window into the mechanisms by which we regulate conscious awareness," he says.

Funding for this research originally came in 1999 from a University of Oregon summer research award. In March 2000, Anderson received $750,000 from the National Institute of Mental Health that he will use to continue work in this area.

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