Updated

If you’re planning to go cold turkey this Thanksgiving season, you better have strong convictions to break an old habit.

A new study shows that old habits, such as smoking, will creep back over time simply because they are “learned behaviors” that are automatically recalled by your unconscious memory, especially in times of stress.

The news comes just days before millions of the nation’s smokers will be encouraged to say “no thanks” to cigarettes for at least 24 hours in recognition of The Great American Smokeout (search). This year’s event, sponsored by the American Cancer Society, will be held on Nov. 18.

For the study, researcher Cindy Lustig, PhD, investigated why old habits always seem to win out despite one’s good intentions. Forty-eight undergraduate students at Washington University learned two different ways of responding to certain cue words. For example, they were instructed to “Say ‘cup’ when you see ‘coffee,’” and then told to “Say ‘mug’ when you see ‘coffee’”.

After learning the new behaviors, the participants underwent memory tests both immediately after learning the words and the day after.

Some of the students were told to specifically answer in a certain way — to respond using only the originally learned word "cup." The other groups were allowed to answer freely using either the words "cup" or "mug."

Lustig and her colleagues found that those who were told to control their response recalled the correct words on both days of memory testing.

However, those who responded with whichever came to mind — either cup or mug — showed an even split between the two word choices on the first day but, on the second day, the word “cup” became the more prevalent answer.

The researchers say the finding shows that the second response (the word “mug”) “seemed to fade from memory” while the first response (the word “cup”) maintained a stronger position in one’s mind.

It is unclear why “original responses maintain their strength better than new response over long delays,” the researchers wrote in the November issue of Psychological Science.

According to the journal article, one theory is that people use their “best” brain power when learning an original list, or habit, and do not commit later lists to memory as strongly.

The findings could help explain why smokers, for example, crave a cigarette when under stress. Our old habits become more automatic over time. Stress doesn’t just wreak havoc on our physical being; it can also disrupt our capacity to control our memory and behaviors. As a result, lifelong habits, which are automatically stored in our subconscious, become more influential.

By Kelli Miller Stacy, reviewed by Brunilda Nazario, MD

SOURCES: Lustig, C. Psychological Science, November 2004; vol 15: no. 11. News release, University of Michigan.