Implicit memory is sometimes referred to as unconscious memory or automatic memory. Implicit memory uses past experiences to remember things without thinking about them. The performance of implicit memory is enabled by previous experiences, no matter how long ago those experiences occurred.

A subset of implicit memory, procedural memory, enables us to perform many everyday physical activities, such as walking and riding a bike, without having to give it thought. A large majority of implicit memories are procedural in nature. Procedural memory primarily involves learning new motor skills and depends on the cerebellum and basal ganglia.

Priming is another, smaller subset of implicit memory. It involves using pictures, words or other stimuli to help someone recognize another word or phrase in the future. Examples include using green to remember grass and red to remember apple.

Examples of implicit memories

Recalling the words to a song when someone sings the first few wordsRiding a bikePerforming simple cooking tasks, such as boiling water for pastaDriving a carTaking a familiar route each day, such as commuting to work or the store where you shop frequentlyButtoning a shirtCompleting tasks that are a routine part of a familiar job, such as sanding for a carpenter or chopping onions for a chefRecalling the rules of a simple and familiar game, such as tag or solitaireDialing a phoneBrushing your teethTyping on a keyboard

Differences between implicit and explicit memory

Implicit memory differs from explicit memory, also called declarative memory, which involves a conscious attempt to retrieve memories of past events. While implicit memory requires little if any effort to recall, explicit memory requires a more concerted effort to bring memories to the surface. While most people can tick off the days of the week from the time they are in grade school — which is implicit memory — it takes explicit memory to recall that you have a dentist appointment next Tuesday.

Other examples of explicit memory:

Knowing that the battles of Lexington and Concord started the Revolutionary WarRemembering your trip to Italy last summerRecalling the events of Hurricane Katrina

Testing implicit memory

In a 1977 experiment, participants were asked to read 60 believable statements every two weeks and to rate them based on their validity. This was a test of the illusion-of-truth effect — that a person is more likely to believe a familiar statement than an unfamiliar one. Participants were more likely to rate as true statements the ones they had previously heard — even if they didn't recall having heard them — regardless of the truth of the statement.

In a 1984 experiment of implicit memory by Peter Graf, Larry Squire and George Mandler, brain-damaged participants and a control group were asked to study lists of words and attempt to recall them in any order. The control group performed much better on this task than the participants with brain damage. To test their implicit memory, both groups studied the lists of words but were tested by being shown three-letter portions of words with the instruction to produce the first word that came to mind in response to each. Participants would get "cha" and be asked to say the first word that came to mind. The word chair — which had been on the list in the previous portion of the test — in the list primed both groups to produce that word rather than another on the test, indicating that people suffering from brain damage still have their implicit memory in tact.

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