Memory: Foundations, Processes, and Errors in Human Memory

Topic 7: Memory

Introduction to Human Memory

Memory is the process by which we encode, store, and retrieve information. It is not static and can change over time. Our brains often "fill in the gaps" in memory, which is generally adaptive but can lead to errors. Memory is reconstructive, meaning it can be influenced by new information and cognitive structures.

• Definition: Memory refers to the mental processes involved in acquiring, storing, and retrieving information.

• Key Point: Memory is not a perfect recording device; it is dynamic and subject to change.

• Example: Beth Loftus compares memory to a Wikipedia page—editable by oneself and others.

Foundations of Memory

Encoding, Storage, and Retrieval

Memory involves three fundamental processes: encoding (initial recording of information), storage (saving information for future use), and retrieval (recovering stored information).

• Encoding: Transforming sensory input into a form that can be stored.

• Storage: Maintaining encoded information over time.

• Retrieval: Accessing stored information when needed.

Three-Stage Model of Memory

Sensory Memory, Short-Term Memory, Long-Term Memory

The three-stage model describes how information passes through different types of memory, each with distinct span and duration.

• Sensory Memory: Brief storage of sensory events (sights, sounds, tastes).

• Short-Term Memory (STM): Limited capacity system, retains information for up to 30 seconds.

• Long-Term Memory (LTM): Continuous, potentially lifelong storage of information.

Information must travel through all stages to be remembered: SENSORY → STM → LTM

Sensory Memory

Characteristics and Types

Sensory memory stores brief sensory events with high precision. Each sense has its own sensory memory.

• Iconic Memory: Visual system, duration < 1 second.

• Echoic Memory: Auditory system, duration 2-3 seconds.

• Snapshot: Stores sensory info; lost unless transferred to other memory types.

Short-Term Memory (STM)

Capacity and Duration

STM is a limited capacity system where information is retained for only a short period unless actively maintained.

• Capacity: 7 ± 2 items (the "magic number 7").

• Duration: Up to 30 seconds without rehearsal.

• Fate: Information is either discarded or stored in LTM.

Extending STM Capacity: Chunking

Chunking involves organizing large bodies of information into smaller, meaningful groups to extend STM span.

• Example: Grouping random letters into familiar acronyms or words.

Rehearsal: Transferring from STM to LTM

Types of Rehearsal

• Maintenance Rehearsal: Repeating stimuli in the same form.

• Elaborative Rehearsal: Organizing and linking information in meaningful ways; more effective for transfer to LTM.

• Memory Consolidation: The process by which rehearsal leads to stable long-term memories.

Working Memory

Active Processing and Central Executive

Working memory is a set of temporary stores that actively manipulate and rehearse information. It includes a central executive processor involved in reasoning and decision-making.

• Mental Whiteboard: Used for holding and processing information in real time.

Long-Term Memory (LTM)

Characteristics

• Continuous Storage: May last decades or a lifetime.

• No Limit: Comparable to a computer's hard drive.

• Amnesia Evidence: Anterograde vs. retrograde amnesia shows distinction from STM.

Types of Long-Term Memory

Type	Subtypes	Description
Declarative (Explicit)	Semantic, Episodic	Conscious recollection of facts/events
Non-declarative (Implicit)	Procedural, Priming	Unconscious memory for skills/behaviors

The Serial Position Effect

Primacy and Recency Effects

• Primacy Effect: Better recall for items presented first.

• Recency Effect: Better recall for items presented last.

• Odd/Unique Stimuli: Remembered regardless of position.

Case Studies in Memory

Henry Molaison (HM)

• Hippocampus removed to treat seizures.

• Could not form new explicit memories; could learn new skills (mirror tracing).

• Distinction between explicit and implicit memory.

Clive Wearing

• Severe anterograde and retrograde amnesia due to viral encephalitis.

• "30 second Clive"—cannot form new memories, but can still play piano.

• Suggests distinction between declarative and non-declarative memory.

LTM: Declarative Memory

Explicit Memory

• Semantic Memory: General knowledge (e.g., knowing the prime minister).

• Episodic Memory: Recollection of personal events (e.g., first kiss, first day of university).

LTM: Non-declarative Memory

Implicit Memory

• Procedural Memory: Memory for how to do things (e.g., tie your shoes).

• Priming: Activation of stored information to help identify new information faster.

Neuroscience of Memory

Brain Structures and Processes

• Karl Lashley & Engram: Memory traces distributed throughout the brain.

• Hippocampus: Critical for memory consolidation and encoding new declarative memories.

• Amygdala: Involved in emotional memories (e.g., traumatic experiences, phobias).

Long-Term Potentiation

• Neural pathways become more easily excited during learning.

• "Neurons that fire together, wire together."

• Synapses between neurons increase, dendrites branch out.

Why Do We Forget?

Encoding Failures

• Failure to attend to information prevents encoding.

• Most events are never encoded.

• Self-reference effect: Better memory for information related to oneself.

• Stress: Reduces accuracy of eyewitness recall; can focus attention but also impair identification.

• Own age bias & Cross race effect: Difficulty encoding faces of different ages/races.

Retrieval Failures

• Decay: Information fades over time.

• Interference: Competition with new information.

• Proactive Interference: Old information interferes with new learning.

• Retroactive Interference: New information overshadows older memories.

Amnesia

Types of Amnesia

• Anterograde Amnesia: Inability to remember new information after trauma; often involves hippocampal damage.

• Retrograde Amnesia: Loss of memory for events prior to trauma.

Retrieving Memories

Recall and Recognition

• Recall: Accessing information without cues (e.g., short answer test).

• Recognition: Identifying previously learned information (e.g., multiple-choice questions).

• Tip-of-the-tongue Phenomenon: Knowing information but unable to retrieve it; sometimes aided by related cues.

Levels of Processing Theory

Depth of Processing

• Deeper, more meaningful processing leads to better memory retention.

• Shallow Processing: Focus on physical/sensory aspects (e.g., memorizing key terms).

• Deep Processing: Analyzing meaning and connections to existing knowledge.

Encoding Specificity

Context and State-Dependent Learning

• Context-dependent: Better recall when retrieval context matches encoding context (e.g., classroom).

• State-dependent: Better recall when internal state matches encoding state (e.g., mood, intoxication).

Flashbulb Memory

Emotionally Charged Memories

• Records of atypical, unusual events with strong emotional associations.

• Exceptional memories are more easily retrieved, though not always accurate.

• Examples: Assassinations, Moon landing, 9/11 attacks.

Memory is Reconstructive

Influences on Memory

• Memories change over time and can be influenced by stereotypes, schemas, scripts, and post-event information.

• Important implications for legal settings (e.g., courtroom testimony).

Schemas & Scripts

Organized Knowledge Structures

• Schemas/scripts are mental models used to "fill in the gap" in memory.

• Memory may be distorted to conform with schema/script (e.g., robbery script study).

• Stereotypes can also influence memories.

Memories are Suggestible

Suggestibility and False Memories

• Suggestibility: Effects of misinformation from external sources leading to false memories.

• Memories are fragile and vulnerable to suggestion.

• Eyewitness testimony is a key area of study.

The Misinformation Effect

Post-Event Information

• Post-event information can alter or become incorporated into original memory (Loftus, 1974).

• Leading questions can change what is remembered (e.g., "How fast were the cars going?").

False Memories

Research Findings

• Loftus (1997): 25% of participants remembered an implanted memory after two interviews.

• Hyman et al. (1997): 27% accepted a false memory after suggestion.

Mandela Effect

Collective False Memories

• Mandela Effect: Large groups of people remember events or details incorrectly (e.g., "Looney Tunes" vs. "Looney Toons").

Laboratory Induction of False Childhood Memories

Implanting False Memories

• Researchers have implanted a variety of false memories (e.g., being attacked by a dog, meeting Bugs Bunny at Disneyland).

Memory Hacker (Shaw & Porter, 2015)

Implantation of False Memories

• Controversial study: 70% of participants were successfully implanted with a false memory of committing a crime.

• Method: Three interviews with college students.

Eyewitness Misidentification

Leading Cause of Wrongful Convictions

• Eyewitness misidentification is the leading cause of wrongful convictions in DNA exoneration cases.

Leading Cause	Percentage
Eyewitness misidentification	~70%
Forensic science	~20%
False confession	~10%
Informant	~5%

Line-up Procedures

Identification in Legal Contexts

• Witnesses identify a culprit from a lineup or photo array.

• Lineups contain the suspect and a set of foils or distractors.

Case Example: Ronald Cotton

Eyewitness Misidentification

• Ronald Cotton was wrongfully convicted due to eyewitness misidentification, highlighting the fallibility of memory in legal contexts.