Learning may be unconscious and happen even when people are not aware of their learning experience. The research comes out in the July 28, 2005 issue of Nature.
Researchers from University of California, San Diego School of Medicine and the San Diego Veterans Affairs Health System had undertaken the study to find out if like animals humans could learn through habits formed even when they are actually not aware of doing so.
Habit learning occurs when information is stored unconsciously, through repetition and trial-and-error learning. These memories are retained in a different region of the brain, called the basal ganglia. Declarative memory, on the other hand, is based on active learning and memorization, and is dependent on a region of the brain in the temporal lobe that includes the hippocampus. When the hippocampus and related structures are destroyed, the human patient loses the ability to learn new memories and to access recent memories.
In monkeys with lesions in the hippocampus, it had been shown that in contrast to humans with similar hippocampal lesions due to injury or disease who have difficulty learning certain tasks over a certain time period, the monkeys can learn the tasks at a normal rate, apparently as habits.
Researchers had speculated that humans might have the same capacity to acquire habit memory, but that this capability is ordinarily obscured by our excellent capacity to learn by conscious memorization.
In the study reported in Nature, two human volunteers with amnesia, called EP and GP, participated in a series of simple object discrimination tasks. Both individuals have severe memory impairment, due to temporal lobe damage caused by herpes simplex encephalitis.
At the beginning of each session, the volunteers had no recollection of having performed the task previously, and even after several sessions they could not explain what they were being asked to do or why. But, after several sessions of repeating the exercise with the same pairs of objects, the volunteers unconsciously selected the correct item in each pair with increasing accuracy. By the end of the study they were scoring 95% and 100% in their selection of the correct item.