There is evidence suggesting that different processes are involved in remembering something versus knowing whether it is familiar. It appears that "remembering" and "knowing" represent relatively different characteristics of memory as well as reflect different ways of using memory. To remember is the conscious recollection of many vivid contextual details, such as "when" and "how" the information was learned. Remembering utilizes episodic memory and requires a deeper level of processing (e.g. undivided attention) than knowing. Errors in recollection may be due to source-monitoring errors that prevent an individual from remembering where exactly a piece of information was received. On the other hand, source monitoring may be very effective in aiding the retrieval of episodic memories. Remembering is a knowledge-based and conceptually-driven form of processing that can be influenced by many things. It is relevant to note that under this view both kinds of judgments are characteristics of individuals and thus any distinctions between the two are correlational, not causal, events. To know is a feeling (unconscious) of familiarity. It is the sensation that the item has been seen before, but not being able to pin down the reason why. Knowing simply reflects the familiarity of an item without recollection. Knowing utilizes semantic memory that requires perceptually based, data-driven processing. Knowing is the result of shallow maintenance rehearsal that can be influenced by many of the same aspects as semantic memory. Remember and know responses are quite often differentiated by their functional correlates in specific areas in the brain. For instance, during "remember" situations it is found that there is greater EEG activity than "knowing", specifically, due to an interaction between frontal and posterior regions of the brain. It is also found that the hippocampus is differently activated during recall of "remembered" (vs. familiar) stimuli. On the other hand, items that are only "known", or seem familiar, are associated with activity in the rhinal cortex.
Origins The remember-know paradigm began its journey in 1985 from the mind of Endel Tulving. He suggested that there are only two ways in which an individual can access their past. For instance, we can recall what we did last night by simply traveling back in time through memory and episodically imagining what we did (remember) or we can know something about our past such as a phone number, but have no specific memory of where the specific memory came from (know). Recollection is based on the episodic memory system, and familiarity is based on the semantic memory system. Tulving argued that the remember-know paradigm could be applied to all aspects of recollection. In 1988 the application of the paradigm was refined to a set of instructions that could elicit reliable judgments from subjects that can be found using many variables. The remember-know paradigm has changed the way in which researchers can study memory tasks and has had implications on what were originally considered purely "episodic" memories, which can now be thought of as a combination of both remembering and knowing or episodic and semantic.
Possible theories Remembering and knowing have been linked to dual-component theories, as well as unitary trace-strength/signal detection models.
Tulving's theory Episodic and semantic memory give rise to two different states of consciousness, autonoetic and noetic, which influence two kinds of subjective experience: remembering and knowing, respectively. Autonoetic consciousness refers to the ability of recovering the episode in which an item originally occurred. In noetic consciousness, an item is familiar but the episode in which it was first encountered is absent and cannot be recollected. Remembering involves retrieval from episodic memory and knowing involves retrieval from semantic memory. In his SPI model, Tulving stated that encoding into episodic and semantic memory is serial, storage is parallel, and retrieval is independent. By this model, events are first encoded in semantic memory before being encoded in episodic memory; thus, both systems may have an influence on the recognition of the event.
High-threshold model The original high-threshold model held that recognition is a probabilistic process. It is assumed that there is some probability that previously studied items will exceed a memory threshold. If an item exceeds the threshold then it is in a discrete memory state. If an item does not exceed the threshold then it is not remembered, but it may still be endorsed as old on the basis of a random guess. According to this model, a test item is either recognized (i.e., it falls above a threshold) or it is not (i.e., it falls below a threshold), with no degrees of recognition occurring between these extremes. Only target items can generate an above-threshold recognition response because only they appeared on the list. The lures, along with any targets that are forgotten, fall below threshold, which means that they generate no memory signal whatsoever. For these items, the participant has the option of declaring them to be new (as a conservative participant might do) or guessing that some of them are old (as a more liberal participant might do). False alarms in this model reflect memory-free guesses that are made to some of the lures. This simple and intuitively appealing model yields the once-widely-used correction for guessing formula, and it predicts a linear receiver operating characteristic (ROC). An ROC is simply a plot of the hit rate versus the false alarm rate for different levels of bias. A typical ROC is obtained by asking participants to supply confidence ratings for their recognition memory decisions. Several pairs of hit and false alarm rates can then be computed by accumulating ratings from different points on the confidence scale (beginning with the most confident responses). The high-threshold model of recognition memory predicts that a plot of the hit rate versus the false alarm rate (i.e., the ROC) will be linear it also predicts that the z-ROC will be curvilinear.
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