Memory is a complex sequence of mental processes that encode, store, and retrieve information. Several models were developed to explain how memory works, but research used to show a lot of contradiction. For example, flashbulb memory was considered a separate mechanism than long-term memory because the level of detail recalled was closer to sensory memory than long-term memory. However, because of advanced mapping technologies, researchers today are capable of providing better descriptions of the processes and regions involved in memory storage and retrieval.
In the beginning of research, studies focused on creating general theories, which were studies by observing and measuring the performance of memory tasks. Those types of models incorporated constraints that were supposed to apply to all activities, but as complex processes, such as decision-making or solving problems, became the objective in studies, researchers had to develop specific models that accounted for background skills, knowledge, and sequencing of processes (Ericsson & Kintsch, “Long-term Working Memory”).
In traditional theories, short-term memory storage received information from sensory memory and later passed it into long-term memory. However, several arguments were placed against long-term memory because researchers argued that it is not possible to expect which information will be relevant in the future, so people could not consciously decide which memory will be stored for later retrieval (Ericsson & Kintsch, “Long-term Working Memory”).
Long-term working memory was largely ignored by the scientific community during the 1960s, and a lot of emphasis was placed on investigating working memory with a focus on the available information in short-term storage; later in the 1980s, newer models decided to define working memory as an active portion of long-term memory (Ericsson & Kintsch, “Long-term Working Memory”). Finally, it was discovered that working memory is not a single system, but it is a combination of subsystems that work independently to complete different tasks, such as receive sensory information, sort sensory information based on attention directions, encode it into short-term memory, and eventually encode it into long-term memory as long as the person rehearses the information frequently.
Sensory memory has the shortest span because the sensory organs that receive information from the environment have a large capacity, but keep the information for less than three seconds. It is generally agreed that sensory memory is a raw image or sensation that is not bound and does not form coherent objects (Sligte et al., “Detailed Sensory Memory”). Only when the information is processed by working memory, some of the information is retained.
Sensory memory is divided into several types. For example, when referring to visual memory, the term “iconic memory” is used. Iconic memory describes the first of the three stages the current model of visual sensory memory uses to explain the transition from sensory memory to short-term memory (Sligte et al., “Detailed Sensory Memory”). Research shows that people retain less than 25 percent of the information in their short-term memory in contrast to the amount of information stored in iconic memory, which lasts 0.5 seconds and decreases with age (Sligte et al., “Detailed Sensory Memory).
Although sensory memory is vivid, it does not last long in its raw state before it is forgotten or absorbed and reorganized by working memory. However, some researchers suggested that a certain phenomenon, referred to as “flashbulb memory,” is responsible for creating vivid and permanent memories that can be triggered later in life, and it was considered that a special mechanism governed the creation of this type of memory (McCloskey, Wible, and Cohen 171).
However, arguments and evidence presented to support the existence of a flashbulb memory were not always accurate, clear, or considered reliable (McCloskey, Wible, and Cohen 171). Previous studies did emphasize the immunity of flashbulb memories to forgetting, but the study by McCloskey, Wible, and Cohen proved that both accuracy and longevity of those types of memories are insufficient, so it is not possible to suggest that a separate mechanism governs these types of memories.
Working memory is an executive function that is essential for proper memory functions because impairments in the associated regions of the brain are linked to attention-deficit/hyperactivity disorder and other memory-related issues. Working memory is sometimes used as a synonym for short-term memory, but the working memory mechanisms are also responsible for actively manipulating information (Alderson et al. 827).
Working memory is divided into the central executive system, the phonological buffer/loop and visual-spatial sketchpad (Alderson et al. 827). Neurophysiological and neuroimaging studies found that all three working memory systems are independent and each system has a specific task, so the central executive system determines attention and organizes acquired information while the other two systems are responsible for short-term memory (Alderson et al. 828).
If the information is not processed by the central executive system, it will not become a part of the long-term memory and will be forgotten within 20 seconds. However, research on short-term memory showed several patterns in recalling information from short-term memory. Ebbinghaus was the first researcher who derived the general laws governing memory recall when performing simple task and one of those findings was the serial position effect, which occurs in free recall (Ericsson and Kintsch, “Long-term Working Memory”).
The serial position effect suggested that people will always recall recent items first and initial items second in free recall experiments. Those phenomena were referred to as the recency effect and the primacy effect. However, various studies suggested that too many factors, including list length, term similarity, and presentation, can affect the recency recall results, so a model was developed to explain human memory as a two-store mechanism composed of short-term memory and long-term memory (Howard and Kahana 923).
The two-store model was significantly criticized during the 1970s, but there were no valid conclusions or evidence that could support either side of the debate (Howard and Kahana 924). Because of the complexity of free recall, it was not possible to create a unified conclusion. One of the possibilities found by Howard and Kahana is the role of variable context in free call, and that process is considered the most important because it explains the existence of the long-term lag recency effect (936).
Although the two-store model is still used to day because it includes the short-term and long-term memory mechanisms, memory is further divided into several subtypes. For example, memory can be divided into implicit and explicit or procedural and declarative memory. Implicit memory is similar to procedural memory because it does not require conscious awareness, but it does use previous experience as an aid in task performance accuracy and results. Explicit memory is a conscious recollection of information, such as remembering previous events or future appointments.
In research, implicit tasks and explicit tasks are often used to measure differences in performance. For example, implicit tasks may require showing pictures of famous people and unknown people and requiring them to judge the fame of the person while explicit tasks may include recalling faces seen during the implicit tasks (Henson et al. 179). With measuring implicit and explicit memory effects on
Procedural memory is a form of automation of tasks, so people do not require awareness to complete them. Unlike declarative memory, which is a recollection of events or facts that can be verbalized, procedural memory is implicated in motor learning. The model three-stage model developed by Fitts and Posner can be applied to learning any new skill at any stage of development, and it includes the cognitive, associative, and autonomous stage (12). While the person learning a new skill is concerned with cognitive processes during the first stage, the movement becomes a part of procedural memory in the third stage and is independent of cognitive processes.
Another example is the division of memory into semantic memory and episodic memory, and both types of memory are subtypes of declarative memory. Semantic memory is comprised of facts while episodic memory is comprised of events. Both types of memory are linked to the hippocampal system because magnetic resonance shows that the region is damaged in people with memory impairment (Vargha-Khadem et al. 376).
However, findings from several studies suggested that only episodic memory is dependent on the hippocampal system while semantic memory depended mainly on underlying cortices (Vargha-Khadem et al. 376). The explanation of their finding is supported by the evidence found from amnesic patients who suffered from episodic memory loss. Because episodic memory is context-rich, it requires significant processing in the hippocampal system while semantic memory is context-free, so underlying cortices can support it and maintain even when the hippocamal system becomes damaged (Vargha-Khadem et al. 379).
Forgetting can occur in several stages of information acquisition, even without damage to relevant systems or disorders. When information is received in sensory memory, it is forgotten soon if the central executive system does not allocate attention to the data in question. Otherwise, it is transferred into short-term memory where it can last for up to 20 seconds before it is transferred into long-term memory. If encoding does not occur or the person does not use the information, it is lost before being stored in long-term memory.
However, even when stored in long-term memory, impaired recall can block the information or cause forgetting. Three assumptions were created from early research in recall impairment. It was considered that memories compete for access when they are being recalled; the strength of association determines the priority of recalling memories; frequency of retrieval was associated with subsequent priority when recalling information (Anderson, R. Bjork, and E. Bjork 1063). With that in mind, it is possible to notice that retrieving the same information will cause retrieval-induced forgetting of other related information. While retrieval-induced forgetting is a confirmed effect, a study by Anderson, R. Bjork, and E. Bjork (1082) showed that retrieval suppression, rather than strength-dependent competition, was the main cause forgetting.
Various disorders that impair memory are linked to genetics. For example, Alzheimer’s disorder is three times more prevalent among people who have a family history of Alzheimer’s (Valo and Wabler, “Alzheimer’s Disease”). There is no cure for Alzheimer’s at the moment, and there is no therapy that could slow down the progress of the disorder, so the best protection is to control the risk factors associated with the onset of Alzheimer’s (Alzheimer's Association, “Basics of Alzheimer's”). Current findings link obesity, hypertension, abnormal cholesterol levels, tobacco, and alcohol, lack of social interactions, sedentary lifestyle, and lack of cognitive activity with the development of Alzheimer’s disease (Valo and Wabler, “Alzheimer’s Disease”).
However, even in healthy individuals, false memories are often present. Most early research on false memories suggested that it is possible to induce them, but contradictory results showed the necessity for better research methods and powerful materials to induce stronger false memory effects (Roediger and McDermott 804).
Furthermore, a study by Roediger and McDermott proved that false memories can also be a product of conscious recollection rather than manipulated effects (811). The implication of their research was significant because it revealed the notion that memory can be divided into reproductive and reconstructive as ill-founded. According to Bergson, accurate memory, memory-image, and perception are three different processes that occur simultaneously, and they all affect quality of perception (237). When people retrieve memories, affection and mental states interfere with the accuracy of data retrieved because they determine the interpretation of the input received from the memory, so false memories are an integral part because raw information is adapted and categorized in compliance with emotional and mental states.
It is possible to notice that a lot of early research on memory was inconclusive and relied heavily on theory and observing the correlation between memory and simple tasks. Over time, scientists started to observe complex processes that required the development of several models for researching the systems and processes involved in memory encoding, storage, and retrieval. Modern technologies in brain mapping also assisted in improving the understanding of memory, and it is possible to expect that those findings will have several clinical implications after being tested in clinical trials.
Works Cited
Alderson, R. Matt et al. “Working Memory Deficits in Adults with Attention-Deficit/Hyperactivity Disorder (ADHD): An Examination of Central Executive and Storage/Rehearsal Processes.” Journal of Abnormal Child Psychology 36.6 (2008): 825-837. Print.
Alzheimer's Association. Basics of Alzheimer's disease. [Brochure], 2010. Web. 27 April 2013.
Anderson, Michael C., RobertA Bjork, and Elizabeth L. Bjork. "Remembering Can Cause Forgetting: Retrieval Dynamics in Long-term Memory." Journal of Experimental Psychology-Learning Memory and Cognition 20.5 (1994): 1063-1087. Web. 27 April 2013.
Bergson, Henri. Matter and Memory. New York, NY: Cosimo, Inc, 2007. Print.
Ericsson, K. Anders, and Walter Kintsch. "Long-term Working Memory." Psychological Review 102.2 (1995): n. pag. Web. 27 April 2013.
Fitts, Paul, and Michael Posner. Human performance. Oxford, England: Brooks and Cole, 1967. Print.
Henson, R. N. A., et al. "Face Repetition Effects in Implicit and Explicit Memory Tests as Measured by fMRI." Cerebral Cortex 12.2 (2002): 178-186. Print.
Howard, Marc W., and Michael J. Kahana. "Contextual Variability and Serial Position Effects in Free Recall." Journal of Experimental Psychology: Learning, Memory, and Cognition 25.4 (1999): 923-941. Web. 27 April 2013.
McCloskey, Michael, Cynthia G. Wible, and Neal J. Cohen. "Is There a Special Flashbulb-Memory Mechanism?." Journal of Experimental Psychology General 117 (1988): 171-181. Web. 27 April 2013.
Roediger, Henry L., and Kathleen B. McDermott. "Creating False Memories: Remembering Words Not Presented in Lists." Journal of Experimental Psychology-learning memory and cognition 21.4 (1995): 803-814.
Rovee-Collier, Carolyn. "Dissociations in Infant Memory: Rethinking the Development of Implicit and Explicit Memory." Psychological Review 104.3 (1997): 467-498. Print.
Sligte, Ilja G., et al. "Detailed Sensory Memory, Sloppy Working Memory." Frontiers in Psychology 1 (2010), n.pag. Web. 27 April 2013.
Valo, Jamie, and Sarah Wabler. Alzheimer's Disease [PDF document], 2006. Web. 27 April 2013.
Vargha-Khadem, Faraneh, et al. "Differential Effects of Early Hippocampal Pathology on Episodic and Semantic Memory." Science 277.5324 (1997): 376-380. Print.
