Recognition memory is the type of memory that lets a person know that a certain stimulus has been encountered before. A type of declarative memory, there are two ways that this type of memory is processed — as recollection or as familiarity. In both cases, a person needs to be presented with a stimulus before a memory is triggered. Once a stimulus has triggered a person's recognition memory, the memories that resurface can fall anywhere along a scale from a hazy feeling that a certain event or stimulus has been experienced before to recall of intricate details about a past experience.
The formal study of recognition memory began in the 1800s and has continued as new discoveries in brain science are made. Early researchers claimed that people would utilize recognition memory only when the mind was not functioning at its peak capacity. In 2011, brain scientists understand that recognition memory serves a variety of functions, as many details can be forgotten by a fully functioning, healthy brain until they are needed, when an analogous or similar situation is presented. At that time, the brain is able to recall past events and the person can make decisions based on prior experience and the memories that have been recently recalled.
There are two main types of recognition memory, which fall at opposite ends of a spectrum. The first is familiarity, in which a person has a vague feeling that a certain stimulus or situation has been encountered before. The other type of recognition memory is recollection, in which details of a past experience resurface in response to a similar new experience. The details in these memories can be either vague or specific, often depending on how much detail the brain needs to make a new decision.
Recognition memory is a type of declarative memory. These memories are stored in a person's long term memory and can usually be called upon at will. Though recognition memory may be buried until it is stimulated, a person can consciously choose to examine pieces of this information, making it different from other types of long term memory, such as those memories that allow a person to ride a bicycle after many years without thinking about the mechanics of doing so. The memories stored in the declarative memory can be called up and examined as the need for them arises.