Source amnesia is the inability to remember where, when or how previously learned information has been acquired, while retaining the factual knowledge. This branch of amnesia is associated with the malfunctioning of one's explicit memory. It is likely that the disconnect between having the knowledge and remembering the context in which the knowledge was acquired is due to a dissociation between semantic and episodic memory – an individual retains the semantic knowledge (the fact), but lacks the episodic knowledge to indicate the context in which the knowledge was gained.
Memory representations reflect the encoding processes during acquisition. Different types of acquisition processes (e.g.: reading, thinking, listening) and different types of events (e.g.: newspaper, thoughts, conversation) will produce mental depictions that perceptually differ from one another in the brain, making it harder to retrieve where information was learned when placed in a different context of retrieval. Source monitoring involves a systematic process of slow and deliberate thought of where information was originally learned. Source monitoring can be improved by using more retrieval cues, discovering and noting relations and extended reasoning. However, there are extreme examples of source amnesia caused by a variety of factors.
right|thumb|alt=Drawing of trajectory of tamping iron took through Phineas Gage's skull.|[[Phineas Gage exemplifies an individual who had frontal lobe damage. A large iron rod was driven through his frontal left lobe effecting changes on his personality.]]
Frontal lobe damage
Individuals with frontal lobe damage have deficits in temporal context memory; source memory can also exhibit deficits in those with frontal lobe damage. It appears that those with frontal lobe damage have difficulties with recency and other temporal judgements (e.g., placing events in the order they occurred), and as such they are unable to properly attribute their knowledge to appropriate sources (i.e., have source amnesia). Those individuals with frontal lobe damage have normal recall of facts, but they make significantly more errors in source memory than control subjects, with these effects becoming apparent as shortly as 5 minutes after the learning experience. Individuals with frontal lobe damage often mistakenly attribute the knowledge they have to some other source (e.g., they read it somewhere, saw it on TV, etc.) but rarely attribute it to having learned it over the course of the experiment. It appears that frontal lobe damage causes a disconnection between semantic and episodic memory – in that the individuals cannot associate the context in which they acquired the knowledge to the knowledge itself.
This effect is potentially due to the neuronal loss associated with aging occurring mainly in the frontal lobes. It has been previously noticed that frontal lobe damage can cause source amnesia, so the loss of neurons in this area of the brain associated with aging may very well be the cause of the age-related source amnesia seen. is implicated as a cause of source amnesia. In laboratory conditions, one study found source monitoring to be so poor that the AD participants were correctly performing source memory attributions at approximately chance. relies on judgement processes to examine the qualitative characteristics of the information in order to determine if the information was real or imagined. It appears that individuals with schizophrenia often display failures in monitoring/remembering the source of information, especially for self-generated items The hallucinations that characterize schizophrenia are a result of deficit in reality monitoring – they exhibit an inability to differentiate between internally and externally derived information. Overall, there is evidence of a relationship between source monitoring errors and the disorganized thinking that characterizes those who have schizophrenia Those individuals with PTSD experience memory distortions caused by source amnesia, as well as false memory construction and unintentional integration of information that was not present for the original memory. Not only do individuals with this condition experience less vivid and decontextualized episodic memory for all events outside of the traumatic experience, but also, individuals with PTSD have difficulties with identifying the source of both emotional and neutral information overall. Those with PTSD may have poorer recall for the source of their knowledge due to deficits in the encoding process which creates weaker relationships between the item and its context. These individuals show a memory bias for remembering negative information, possibly due to enhanced amygdala activity during the encoding of emotional (particularly negative) information. Overall, there is a relationship between the emotional arousal of an episode and its source memory – there is some evidence that the enhanced processing of negative memories results in poorer source memory, and thus individuals who are depressed would have increased amounts of source amnesia.
Hypnosis
Hypnosis as a cause of source amnesia involves carrying out hypnosis and having the subjects remember post-hypnotically, experiences they had during hypnosis as tested by asking the individuals about esoteric knowledge that they learned during hypnosis. These individuals typically have no recall of the hypnotic experience whatsoever; however, when tested on these obscure pieces of knowledge they are able to supply the correct answer, demonstrating their source amnesia. The subjects often attribute their knowledge of the obscure facts to learning experiences other than during hypnosis (e.g.: "I read it somewhere," "Somebody must have told me," etc.).
Diagnostic tests
Wisconsin Card Sorting Test (WCST)
The Wisconsin Card Sorting Test is widely used in clinical settings to test for cognitive impairments, such as frontal lobe disorder which has been associated with source amnesia.
;Procedure:
Two sets of 12 identical cards forms the visuo-spatial component for the test. The figures on the cards differ with respect to color, quantity, and shape. The participants are then given a pile of additional cards and are asked to match each one to one of the previous cards.
;Results:
Patients with frontal lobe dysfunction and ultimately source amnesia, will have much greater difficulty finishing this task successfully through method of strategy.
Stroop Color-Naming Task
Research has shown that the Stroop effect has numerous findings related to age and its effect on memory. The test measures speed and accuracy skills of naming colors and colored words, to determine the effects of aging on the brain which is thought to be a cause of source amnesia.
;Procedure:
The participant is asked to read a series of related word-reading and color-naming trials. In the first component of the task, known as the word-reading condition of the task, the participant is asked to read as quickly as possible a series of color names printed either in white or other various colors. The participant is then asked to name the color of a series of colored blocks.
;Procedure:
Showing the participant a list of words and assessing at different time intervals to see if the participant remembers which words were presented and which were not. For example, a list of 15 words could be given to a participant to study from. The experimenter will then test the participant's knowledge of the list 20 minutes later by presenting the list of studied words mixed in randomly with several 'lure' words (words that are semantically similar to the previously studied words but not the same) and new words.
If the participant is successful in this task, they have distinguished between the previously learned words and the lure words.
This experiment can be tested multiple times with the same participant over different time periods (e.g.: 3 months later then tested again 6 months later).
;Results:
Participants are more likely to show source amnesia with the 'lure' words but not with the newly presented words. This means that they confuse the familiarity of the semantically similar words with words that they studied in the original list. This is because content must be encoded along with context in order for the two to be integrated into memory. This suggests that source memory may benefit from thinking about emotions related to the content in order to better encode source related information. This is related to theories on flashbulb memory.
Children
Children are more likely to correctly identify source information if they have been taught to think about the relation between the speaker and the information being shared. This holds true whether the children think about perceptual or emotional ties to the speaker but the effect appears larger when emotional context is considered. The increase in accurate source encoding is not without a cost as it was demonstrated that children who improved their source encoding typically remembered less than controls when it came to recalling semantic or non-source information. In one particular study, older adults were exposed to 8-week long memory training programs. These memory-training programs involved serial memory recall practice using mental imagery as a mnemonic device. Adults involved in the memory-training program showed significant improvement in their source memory specifically. In addition to the memory benefits, increased cortical thickness was shown using MRI scans. Post-event information can come from leading questions, statements made by the media or co-witnesses. This causes grave legal implications given that it can result in wrongful convictions; therefore, it is important that interrogation practices are carefully carried out. However, this slows down the quick retrieval of memory needed in daily life, such as in conversation. This has seen to occur in the music industry and has the implication of copyright infringement over songs, as well as in the formation of scientific research ideas.