Bad habits beat good intentions because learning new habits requires memory control while past behavior becomes automatic.

US psychologists including Cindy Lustig of the University of Michigan in Ann Arbor have shown that fulfilling good intentions is undermined by previously learned habits, which remain strong in more automatic, unconscious forms of memory.

“People usually think of memories as fading as time goes by. In addition, learning new information often interferes with the retrieval of older memories,” the researchers write. “At the same time, old habits are infamous for their ability to return. Both the retroactive interference caused by new learning and the spontaneous recovery of old information after a delay have been observed at least since the classic experiments of Pavlov, but how they occur remains a mystery.”

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