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Memory is essentially the capacity for storing and retrieving information. Three processes are involved in memory: encoding (processing), storage (maintenance), and retrieval (recall). All three of these processes determine whether something is remembered or forgotten.
Types of Memory
Psychologists often make distinctions among different types of memory. There are three main distinctions:
- Implicit versus explicit memory
- Declarative versus procedural memory
- Semantic versus episodic memory
The brain encodes information through sensory input, which is then processed in various regions, such as the hippocampus, in order to form new memories. Declarative memories, or learned knowledge, may be semantic memories, which refer to general facts and information, or episodic memories, which refer to events experienced personally. These two types of memories are part of explicit memory, which requires conscious recall. Implicit memory, on the other hand, involves learned skills and procedures that are recalled unconsciously, referred to as procedural memories, such as riding a bike. Once stored, memories are retrieved through neural networks that involve areas like the prefrontal cortex and the hippocampus. Effective retrieval of all memories depends on the strength of the memory encoding and the cues available, which can differ based on the type of memory being recalled.
It should be noted that although the terms “explicit memory” and “declarative memory” are often used interchangeably, there is a slight distinction between the two. Declarative memories are those that can be consciously recalled and “declared” or verbally expressed. “Explicit memory” is a broader term referring to memories that require conscious effort to retrieve; this includes any memory one is actively aware of recalling. Essentially, declarative memory refers to the content of the memory – facts and experiences – whereas explicit memory refers to the conscious process by which the memory is retrieved. Therefore, the term declarative memory is primarily used when categorizing types of memory based on content (semantic vs. episodic), and the term “explicit memory” is used when discussing the retrieval process, particularly how this type of memory contrasts with implicit memory, which doesn’t require conscious effort. All declarative memory is a type of explicit memory, but the term “explicit memory” emphasizes the conscious retrieval process.
Implicit versus Explicit Memory
Sometimes information that unconsciously enters the memory affects thoughts and behavior, even though the event and the memory of the event remain unknown. Such unconscious retention of information is called implicit memory.
Example: Sophia once visited Hotel California with her parents when she was 10 years old. She may not remember ever having been there, but when she makes a trip there later, she knows exactly how to get to the swimming pool.
Explicit memory is conscious, intentional remembering of information. Remembering a Social Security number involves explicit memory.
Declarative versus Procedural Memory
Declarative memory is recall of factual information such as dates, words, faces, events, and concepts. Remembering the capital of France, the rules for playing football, and what happened in the last game of the World Series involves declarative memory. Declarative memory is usually considered to be explicit because it involves conscious, intentional remembering.
Procedural memory is recall of how to do things such as swimming or driving a car. Procedural memory is usually considered implicit because people don’t have to consciously remember how to perform actions or skills.
Semantic versus Episodic Memory
Declarative memory is of two types: semantic and episodic. Semantic memory is recall of general facts, while episodic memory is recall of personal facts. Remembering the capital of France and the rules for playing football uses semantic memory. Remembering what happened in the last game of the World Series uses episodic memory.
Prospective Memory
Prospective memory is the ability to remember to perform actions in the future. It involves planning or recalling tasks or to-do items, such as remembering to take medication at a certain time, go to an appointment, or send a message later in the day. Unlike retrospective memory, which deals with past events or information, prospective memory focuses on things in the future.
There are two main types of prospective memory: time-based, where actions are triggered by a specific time (e.g., taking a pill at 8:00 a.m.), and event-based, where actions are prompted by a certain event or cue (e.g., giving someone a message when you see them). Effective prospective memory is essential for daily functioning and can be influenced by factors like attention, planning, and distractions.
Memories on Your Nerves
Long-term potentiation (LTP) is a lasting change at synapses that occurs when long-term memories form. Synapses become more responsive as a result. Researchers believe long-term potentiation is the basic process behind memory and learning.
During LTP, repeated stimulation of a neuron leads to increased efficiency in signal transmission between neurons, making it easier for future activation. Essentially, the more often a particular pathway is used in the brain, the stronger and more durable that pathway becomes, which improves memory retention.
The Working Memory Model
Psychologists today consider short-term memory to be a working memory. Rather than being just a temporary information storage system, working memory is an active system. Information can be kept in working memory while people process or examine it. Working memory allows people to temporarily store and manipulate visual images, store information while trying to make decisions and remember a phone number long enough to write it down.
The working memory model, proposed by Alan Baddeley and Graham Hitch in 1974, explains how our primary memory system actively processes information through several components. At the core of this model is the central executive, which directs attention and coordinates activities between two subsystems: the phonological loop and the visuospatial sketchpad. The phonological loop is responsible for processing verbal and auditory information, while the visuospatial sketchpad handles visual and spatial data. These systems work together to manipulate and hold information temporarily, allowing for complex cognitive tasks such as reasoning, problem-solving, and comprehension. Through this dynamic interaction, working memory integrates and organizes information before transferring it to long-term memory, where it can be stored for future use. The working memory model highlights the active and flexible nature of memory processes beyond simple short-term storage.
Multi-Store Model of Memory
After information enters the brain, it has to be stored or maintained. To describe the process of storage, many psychologists use the multi-store model of memory proposed by psychologists Richard Atkinson and Richard Shiffrin in 1968. According to this model, information is stored sequentially in three memory systems: sensory memory, short-term memory, and long-term memory.
Sensory memory briefly holds sensory information, which includes iconic memory (for visual stimuli, lasting about one second) and echoic memory (for auditory stimuli, lasting up to several seconds). Sensory memory has a large capacity, but the information fades quickly unless attended to.
Short-term memory holds information temporarily for about 20 seconds, with a limited capacity of about seven items. Information in short-term memory can be retained using maintenance rehearsal (repeating information to keep it in short-term memory).
Long-term memory stores information for long periods, potentially a lifetime, with an unlimited capacity. It includes explicit memory (facts and experience) and implicit memory (skills and procedures).
This model also highlights the difference between automatic processing, information encoded with little conscious effort (like remembering what you ate for lunch), and effortful processing, which requires attention and rehearsal (like studying for an exam).
The multi-store model has several limitations, including the following:
- Oversimplifies memory processes: The multi-store model presents memory as a linear process where information passes sequentially through three stages. However, research suggests that processes are more complex and involve dynamic interactions between the different memory systems.
- Assumes that short-term and long-term memory are separate systems: The multi-store model treats short-term memory and long-term memory as distinct, but research suggests they interact more closely.
- Overemphasizes Rehearsal for Memory Transfer: The multi-store model suggests that rehearsal is the primary way to transfer information from short-term memory, but research shows that information can enter long-term memory without conscious rehearsal, such as through emotional experiences or automatic encoding.
Levels of Processing Model
The levels of processing model, introduced by Fergus Craik and Robert Lockhart in 1972, suggests that the depth at which information is processed affects how well it is remembered. This model identifies three levels of processing, ranging from shallow to deep: structural, phonemic, and semantic.
Structural processing is the shallowest level, focusing on the physical appearance of words or information, such as recognizing the shape or structure of letters. This type of processing typically leads to weak memory retention.
Phonemic processing involves a slightly deeper level, focusing on how words sound. For example, recognizing rhymes or syllables engages phonemic processing and often results in better retention than structural processing.
Semantic processing is the deepest level and involves thinking about the meaning of the information. This type of processing leads to the strongest memories because it requires active engagement with the content, making it easier to store and retrieve the information later.
According to this model, deeper, more meaningful processing leads to better long-term memory retention than shallow, surface-level processing.
