Memory Systems: Encoding, Storage, and Retrieval

Foundations of Memory as an Information Processing System

• Memory is defined as an information processing system, frequently compared to the functioning of a computer.

• It constitutes a set of processes utilized to encode, store, and retrieve information across various durations of time.

• The three fundamental functions of memory are:

  • Encoding: The process of inputting information into the memory system. This involves labeling or coding sensory information received from the environment, organizing it with similar information, and connecting new concepts to existing ones.

  • Storage: The retention of encoded information over time.

  • Retrieval: The process of getting information out of memory storage and back into conscious awareness.

The Process and Types of Encoding

• Encoding occurs through two primary methods:

  • Automatic Processing: The encoding of details such as time, space, frequency, and the meanings of words without conscious awareness. Examples include recalling what you ate for lunch or the last time you studied.

  • Effortful Processing: The encoding of information that requires significant work and attention. Learning new skills, such as how to drive a car (starting, braking, turning), initially requires effortful processing before the details can be encoded automatically.

• Levels of Meaning in Encoding:

  • Research indicates that material is better encoded when it is made meaningful.

  • In a study by Bransford and McCarrell $(1974)$, participants found sentences like "The notes were sour because the seams split" difficult to recall until provided with context (e.g., "bagpipe"). Other examples included "The voyage wasn't delayed because the bottle shattered" (context: ship christening) and "The haystack was important because the cloth ripped" (context: parachutist).

• The Three Types of Encoding:

  • Semantic Encoding: The encoding of words and their meanings. William Bousfield $(1935)$ demonstrated this by showing that participants asked to memorize $4$ categories of $60$ words total (presented randomly) tended to recall them in related groups.

  • Visual Encoding: The encoding of images. High-imagery, concrete words like "car," "dog," and "book" are easier to recall because they create mental pictures, whereas abstract, low-imagery words like "level," "truth," and "value" are more difficult.

  • Acoustic Encoding: The encoding of sounds, specifically words. This is exemplified by children learning the alphabet through song or the days of the month through the rhyme: "Thirty days hath September, / April, June, and November; / All the rest have thirty-one, / Save February, with twenty-eight days clear, / And twenty-nine each leap year."

• Effectiveness of Encoding Types:

  • Craik and Tulving $(1975)$ found that semantic encoding leads to the best memory of verbal information because it involves a deeper level of processing compared to the shallower visual or acoustic encoding.

  • Self-reference Effect: The tendency for individuals to have better memory for information that relates to themselves compared to material with less personal relevance (Rogers, Kuiper, & Kirker, $1977$).

Stages and Models of Memory Storage

• In order for a memory to become a permanent record, it must pass through three distinct stages of storage, as proposed by Richard Atkinson and Richard Shiffrin $(1968)$.

• The Atkinson-Shiffrin Model: Relates human memory to the way a computer processes information through three stages:

  1. Sensory Memory: Processes environmental stimuli (sights, sounds, tastes). Storage is extremely brief ($up\,to\,a\,couple\,of\,seconds$). If information is not perceived as valuable, it is discarded; if valuable, it moves to short-term memory.

  2. Short-Term Memory (STM): A temporary storage system that processes incoming sensory memory. It lasts approximately $15$ to $30$ seconds.

  3. Long-Term Memory (LTM): The continuous and potentially unlimited storage of information.

• The Baddeley and Hitch Working Memory Model $(1974)$: An alternative model suggesting that short-term memory is not a single store but has different forms (working memory files). These include:

  • Visuospatial Sketchpad

  • Episodic Buffer

  • Phonological Loop

  • Central Executive: Supervises the flow of information between the systems and moves information into long-term memory.

Dynamics of Short-Term Memory

• Capacity:

  • George Miller $(1956)$ famously reported the capacity of short-term memory as the "magic number" $7 ± 2$.

  • Contemporary research by Cowan $(2010)$ suggests the actual capacity is closer to $4 ± 1$.

  • Recall is generally better for random numbers than random letters and slightly better for acoustic encoding (heard) than visual encoding (seen).

• Retention Factors:

  • Memory Trace Decay: The process where a memory trace becomes less activated over time, leading to forgetting. Peterson and Peterson $(1959)$ found trigram recall (e.g., CLS) dropped from $80\%$ after a $3$-second delay to $10\%$ after an $18$-second delay.

  • Proactive Interference: Occurs when previously learned information interferes with the ability to learn new information (Keppel & Underwood, $1962$).

• Rehearsal Techniques:

  • Active Rehearsal: Repeating or practicing information to move it from STM to LTM (e.g., singing the ABCs).

  • Elaborative Rehearsal: Linking new information to existing knowledge (e.g., remembering area code $203$ by associating it with an uncle who lives in that region).

  • Levels of Processing Hypothesis: Proposed by Craik and Lockhart $(1972)$, stating that deeper thought about information leads to better retention.

Characteristics and Organization of Long-Term Memory

• Consolidation: The process of stabilizing a memory trace, taking a few hours at the synaptic level and weeks or longer within the memory system.

• Capacity: Believed to be unlimited.

• Organizational Structures:

  • Semantic (Associative) Networks: Memories are organized into networks of associated concepts. For example, hearing "peanut butter" often triggers the word "jelly."

  • Spreading Activation: Activating one part of the network partially activates linked concepts, making them easier to access. This allows for multiple routes to access information.

  • Hierarchy: Concepts are believed to be arranged hierarchically in the mind.

Taxonomy of Long-Term Memory: Explicit and Implicit

• Explicit (Declarative) Memory: Memories we consciously try to remember and can put into words.

  • Episodic Memory: Accounts of personal experiences (autobiographical events), involving the "what, where, and when" of an event (Tulving, $1972$, $2002$).

  • Semantic Memory: General knowledge, facts, and language-based knowledge (e.g., the definition of psychology or the first African American president).

• Implicit (Non-declarative) Memory: Long-term memories that are not part of our consciousness and are demonstrated through performance.

  • Procedural Memory: Memory for skilled actions or "how-to" information, such as brushing teeth, riding a bicycle, or driving. These are often studied via observable behaviors.

  • Priming: Exposure to a stimulus influences the response to a later stimulus. For example, reading about a picnic might lead one to unscramble "AETPL" as "plate," while reading about flowers might lead to "petal."

  • Emotional Conditioning: Classically conditioned emotional responses to stimuli, such as a specific song or smell triggering nostalgia or positivity without the individual knowing why.

Case Study: Hyperthymesia

• Definition: A highly superior autobiographical memory where individuals can remember almost every event they have experienced.

• Notable Individual: American actress Marilu Henner is one of fewer than $20$ people identified with this ability.

• Onset: Usually appears in adolescence, though some cases in the United States show memory retention from before age $10$.

Mechanisms of Retrieval

• Retrieval is the act of bringing information from storage back into conscious awareness.

• There are three primary methods of retrieval:

  1. Recall: Accessing information without environmental cues (e.g., answering an essay question).

  2. Recognition: Identifying previously learned information upon encountering it again through comparison (e.g., answering a multiple-choice question or recognizing classmates at a reunion).

  3. Relearning: Learning information that was previously acquired. Whitney's ability to quickly pick up Spanish again at age $31$ after a $13$-year hiatus is a prime example of the efficiency of relearning.