Involuntary memory is a sub-component of memory that occurs when cues encountered in everyday life evoke recollections of the past without conscious effort. Voluntary memory, its opposite, is characterized by a deliberate effort to recall the past.
Occurrences There appear to be at least three different contexts within which involuntary memory arises, as described by J.H. Mace in his book Involuntary Memory. These include those that occur in everyday life, those that occur during the processes of voluntary and involuntary recall, and those that occur as part of a psychiatric syndrome.
Precious fragments The most common kind of these phenomena has been termed "precious fragments." This type includes involuntary memories as they arise in everyday mental functioning, which are characterized by their element of surprise: they appear to come into conscious awareness spontaneously. They are the products of common every-day experiences such as eating a piece of cake, bringing to mind a past experience evoked by the taste. Research suggests that such experiences are especially strong and frequent in relation to one's sense of smell. The term "precious fragments" was coined by Marigold Linton, a pioneer in the study of autobiographical memory research. This is reflected, for example, in the narrator of Proust's In Search of Lost Time experience of remembering, upon tasting a madeleine cake in adulthood, a memory from childhood that occurred while eating madeleine dunked in tea.
By-products of other memories These are less common, and appear to be the result of voluntary/involuntary retrieval. Characteristic of such occurrences is the triggering effect this has, as one involuntary memory leads to another and so on. Again, Linton describes her own experiences with such memories as "coming unbidden sometimes when my mind is silent, but also as by-products of searches for other information." Mace terms these “involuntary memory chains,” stating that they are the product of spreading activation in the autobiographical memory system. These involuntary retrievals are experienced when activations are strong or relevant enough to current cognitive activity that they come into consciousness. According to Mace, this suggests that autobiographical memories are organized primarily conceptually (“experiential type concepts: people, places, locations, activities, etc.”), while temporal associations are not retained over time the same way.
Not so precious fragments Finally, some involuntary memories arise from traumatic experiences, and as such are fairly rare compared to other involuntary memories. Subjects describe them as salient, repetitive memories of traumatic events. The troubling nature of such memories makes these occurrences important to clinical researchers in their studies of psychiatric syndromes such as post-traumatic stress disorder. Some researchers have found that involuntary memories tend to have more emotional intensity and less centrality to life story than voluntary memories do. However, one study also shows that recurrent involuntary memories post-trauma can be explained with the general mechanisms of autobiographical memory, and tend to not come up in a fixed, unchangeable form. This suggests that psychologists may be able to develop ways to help individuals deal with traumatic involuntary memories.
Implications for dementia Further research on the automatic nature of involuntary retrieval suggests that they may not require working memory input. Thus, one report hypothesizes that people with dementia may still have available precious autobiographical memories that remain inaccessible until “suitable triggers release them,” prodding at the possibility for caregivers to be trained to reactivate these memories to elicit positive emotional effects and maintain patients’ life stories and sense of identity. Further empirical research is needed, but this insight starts a hopeful path into improving dementia care.
History
Hermann Ebbinghaus
Born in Barmen, Germany in 1850, Hermann Ebbinghaus is recognized as the first to apply the principles of experimental psychology to studying memory. He is especially well known for his introduction and application of nonsense syllables in studying memory, study of which led him to discover the forgetting curve and the spacing effect, two of his most well-known contributions to the field. Ebbinghaus was also the first to attempt a description of involuntary memory, stating that, "often, even after years, mental states once present in consciousness return to it with apparent spontaneity and without any act of the will; that is, they are reproduced involuntarily."Ebbinghaus, H. (1885/1964). Memory: A contribution to experimental psychology, (trans. H.A. Ruger and C.E. Bussenius). Dover, New York. He goes on to explain that these mental states were once experienced, rendering, by definition, their future spontaneous appearance into consciousness the act of remembering, though we may not always be aware of where or how we experienced this information the first time. Ebbinghaus also made the key note that these involuntary reproductions are not random or accidental; instead, "they are brought about through the instrumentality of other immediately present mental images," under the laws of association. This reflects congruence with Mace's and Linton's theory of involuntary memories as by-products of other memories, as discussed above.
Marcel Proust—Proustian memory
Marcel Proust was the first person to coin the term involuntary memory, in his novel À la recherche du temps perdu (In Search of Lost Time or Remembrance of Things Past). Proust did not have any psychological background, and worked primarily as a writer.
Proust viewed involuntary memory as containing the "essence of the past," claiming that it was lacking from voluntary memory. When the protagonist of Proust's novel eats a tea-soaked madeleine, a long-forgotten childhood memory of eating tea-soaked madeleine with his aunt is restored to him. From this memory, he then proceeds to recall the childhood home he was in, and even the town itself. This becomes a theme throughout In Search of Lost Time, with sensations reminding the narrator of previous experiences. Proust dubbed these "involuntary memories".
Current research
Chaining One idea that has recently become the subject of studies on involuntary memory is chaining. This is the concept that involuntary memories have the tendency to trigger other involuntary memories that are related. Typically, it is thought to be the contents of involuntary memories that are related to one another, thereby causing the chaining effect.
In a diary study done by J.H Mace, participants reported that frequently, when one involuntary memory arose, it would quickly trigger a series of other involuntary memories. This was recognized as the cueing source for involuntary memories.
In the work by Bernstein, the diary method was also applied to the study of involuntary memory chaining. The main hypothesis was that chaining would also occur on autobiographical memory tasks. Participants were asked to report the presence of involuntary memories while performing an autobiographical memory task. Results showed that participants did experience involuntary memory recall when they were recalling the past deliberately (also known as voluntary memory). This implies that involuntary memory production occurs as a product of chaining from voluntary memory—the deliberate recall of the past.
Priming A common question in the study of involuntary memory is related to priming; what is it that activates such a memory? Various studies have been conducted in recent years to observe the conditions under which involuntary memories are primed.
Mace, in one of his recent studies, wanted to test the notion that basic cognitive activities, such as thinking about the past, may prime involuntary memories. To test this idea, Mace set up a diary method study in which participants recorded involuntary memories they experienced during a two-week period, in a diary. During this two-week period, participants also had to come into a laboratory at intervals, and were instructed to recall memories from certain life periods (e.g., high school, first five years of marriage). Following this, comparing their involuntary memories to a control condition found that a significant number of their involuntary memories related to the time period they were instructed to recall. Such findings suggest that involuntary memories may be primed by even the simplest of cognitive tasks—namely, reminiscing and recalling the past.
Neurological basis
Research studies regarding the neurological functions of involuntary memory have been few in number. Thus far, only two neuroimaging studies have been conducted comparing involuntary memories to voluntary memories using Positron Emission Tomography (PET).
The first study found that while involuntary memory retrieval is mediated by the hippocampus, a structure of the brain known to be associated with successful episodic memory retrieval, involvement of the hippocampus was independent of whether or not remembering was intentional. The researchers believe this suggests that involuntary memories may reflect the “relative automaticity” of hippocampally-mediated retrieval. However, their research mainly focuses on identifying areas and functions involved in intentional retrieval. Activity in the medial/lateral parietal and right prefrontal cortex was insensitive to depth of encoding, but rather, varied depending on the intentionality of retrieval. These areas were increasingly engaged during intentional retrieval, suggesting that one function of this region may be to align remembering to aid with current behavioral goals.Rugg, M. D., Fletcher, P. C., Frith, C. D., J, R. S., & Dolan, R. J. (1997). Brain regions supporting intentional and incidental memory: a PET study. NeuroReport (Oxford), 8 (5), 1283-1287. This is distinct from involuntary memory, where individuals do not consciously retrieve memories that will be most helpful to their current situation; however, it remains unclear if this process is unconsciously undertaken by the brain. When dealing with involuntary word recognition tasks, activity in areas such as the left inferior frontal gyrus, left superior temporal gyrus, left hippocampus, and right superior occipital cortex have all been implicated. Yet, areas and structures that are uniquely associated with involuntary memory remain unclear and more research is needed to understand the cognitive and neurological basis of this memory phenomenon.