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. Sometimes, our brains "fill in the gaps" to make sense of the world, which can be adaptive but also prone to error. Memory is reconstructive, meaning it can be influenced by various factors and is not a perfect recording device.

• Encoding: Initial recording of information.

• Storage: Information saved for future use.

• Retrieval: Recovery of stored information.

Three-Stage Model of Memory

Overview

Memory is divided into three types, each differing in span and duration. Information must travel through all stages to be remembered.

• Sensory Memory → Short-Term Memory (STM) → Long-Term Memory (LTM)

Sensory Memory

Sensory memory stores brief sensory events, such as sights, sounds, and tastes. Each sense has its own sensory memory, which is very brief and high in precision.

• Iconic memory: Visual system, < 1 second

• Echoic memory: Auditory system, 2-3 seconds

• Acts as a snapshot that stores sensory information

• Unless transferred to other types of memory, it is lost

Short-Term Memory (STM)

STM is a limited capacity memory system where information is retained for only as long as 30 seconds, unless rehearsal is used to retain it longer.

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

• STMs are either discarded or stored in LTM

Extending STM Capacity

STM span can be extended by chunking, which involves organizing large bodies of information into smaller, meaningful groups.

• Example: Grouping letters into familiar acronyms or words

Rehearsal: Transferring from STM to LTM

Rehearsal is the repetition of information that has entered STM, leading to memory consolidation.

• Maintenance rehearsal: Repeating the stimuli in the same form

• Elaborative rehearsal: Considering and organizing information, linking stimuli in meaningful ways; more effective for transfer to LTM

Working Memory

Working memory is a set of active, temporary memory stores that actively manipulate and rehearse information. It contains a central executive processor involved in reasoning and decision-making, acting as a "mental whiteboard."

Long-Term Memory (LTM)

LTM is the continuous storage of information, which may last decades or a lifetime. It has no known limit and is analogous to a computer's hard drive. The distinction between anterograde and retrograde amnesia evidences the separation from STM.

Types of Long-Term Memory

Type	Description	Examples
Explicit (Declarative)	Conscious recollection of facts and events	Semantic (general knowledge), Episodic (personal events)
Implicit (Non-declarative)	Memory without conscious awareness	Procedural (skills), Priming (faster identification)

The Serial Position Effect

The serial position effect describes the tendency to recall stimuli presented first (primacy effect) and last (recency effect) in a list, with odd or unique stimuli also being more memorable.

Case Studies in Memory

• Henry Molaison (HM): Had hippocampus removed, resulting in inability to form new explicit memories but could learn new skills (mirror tracing task). Demonstrates distinction between explicit and implicit memory.

• Clive Wearing: Suffered from anterograde and retrograde amnesia due to encephalitis; could still play piano, showing preserved procedural memory.

Types of Long-Term Memory

Declarative (Explicit) Memory

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

• Episodic memory: Recollection of events in our lives (e.g., first kiss, first day of university)

Non-declarative (Implicit) Memory

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

• Priming: Activation of information already in storage to help identify new information faster

Neuroscience of Memory

Brain Structures Involved

• Hippocampus: Plays a role in memory consolidation and initial encoding; damage leads to inability to process new declarative memories

• Amygdala: Involved with memories involving emotion (e.g., traumatic experiences, phobias)

Long-Term Potentiation

Long-term potentiation is a process where certain neural pathways become easily excited while a new response is being learned. Neurons that fire together, wire together. Synapses between neurons increase, and dendrites branch out.

Forgetting: Causes and Mechanisms

Encoding Failures

• To encode, we must attend to information; most events are never encoded

• Self-reference effect: Better memory for info that relates to oneself

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

• Own age bias and cross-race effect can also lead to encoding failures

Retrieval Failures

• Decay: Information fades over time

• Interference: Loss of information due to competition with new information

• Proactive interference: Old information interferes with new learning

• Retroactive interference: New information overshadows older memories

Amnesia

• Anterograde amnesia: Inability to remember new info after trauma; often due to hippocampal damage

• Retrograde amnesia: Loss of memory for events prior to trauma

Retrieving Memories

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

• Recognition: Identifying information after encountering it again (e.g., multiple-choice questions)

• Tip-of-the-tongue phenomenon: Retrieval failures where information is known but cannot be recalled; sometimes resolved by related cues

Levels of Processing Theory

The depth of information processing during exposure to material is critical. The greater the intensity of initial processing, the more likely we are to remember it.

• Shallow processing: Physical and sensory aspects (e.g., memorizing key terms)

• Deep processing: Analyzing meaning and reflecting on how it relates to existing knowledge

Encoding Specificity

• Context-dependent learning: Better recall when retrieval conditions match encoding conditions (e.g., tested in the same classroom)

• State-dependent learning: Better recall when in the same physiological state as during encoding (e.g., effects of alcohol)

Flashbulb Memory

Flashbulb memories are records of atypical and unusual events with strong emotional associations. These memories are exceptional and more easily retrieved, though not necessarily accurate. Examples include generational reference points such as assassinations or major historical events.

Memory is Reconstructive

Memories change over time and can be influenced by cognitive hardware (stereotypes, schema, scripts) and post-event information. This has important implications for the courtroom.

Schemas & Scripts

• Schemas/scripts: Organized knowledge structures or mental models stored in memory, used to "fill in the gap"

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

• Stereotypes can also influence memories

Suggestibility and False Memories

Suggestibility

• Effects of misinformation from external sources can lead to creation of false memories

• Memories are fragile and vulnerable to suggestion

• Important area of study: eyewitness testimony

The Misinformation Effect

Post-event information can alter or become incorporated into the original memory (Loftus, 1974). Leading questions can change what is remembered.

False Memories

• 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

The Mandela Effect refers to widespread false memories shared by many people, such as misremembering logos or historical facts.

Laboratory Induction of False Childhood Memories

• Researchers have implanted a variety of false memories, including traumatic ones (e.g., being attacked by a dog, meeting fictional characters)

Memory Hacker (Shaw & Porter, 2015)

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

Eyewitness Misidentification

Eyewitness misidentification is the leading cause of wrongful convictions. Line-up procedures involve witnesses identifying a culprit from a lineup or photo array, which contains the suspect and a set of foils or distractors.

Leading Cause	Percentage of DNA Exoneration Cases
Eyewitness misidentification	Highest
Forensic science	Lower
False confession	Lower
Informant	Lowest

Case Example: Ronald Cotton

Ronald Cotton was wrongfully convicted due to eyewitness misidentification, highlighting the fallibility of memory and the importance of accurate procedures in the justice system.