CP Lecture 4 - LT Memory

Declarative (Explicit Memory) — Semantic Memory

• Definition: General, factual knowledge about the world, "undated" (not tied to a specific learning event). It's your internal encyclopedia.

• Distinction: It is a "knowing" of a fact.

• Example: Knowing that Paris is the capital of France, that a canary is a bird, or the rules of soccer.

Declarative (Explicit Memory) — Episodic Memory

• Definition: Memory for specific, personal experiences that are "dated" (tied to a time and place). It's your autobiographical memory.

• Distinction: It is a "remembering" of a personal past.

• Example: Recalling your first day of university, what you ate for breakfast, or your first kiss.

Collins & Loftus Hierarchical Network Model

• A model that organizes semantic memory into a logical hierarchical structure (like a family tree) of interconnected nodes (concepts).

• Representation: Meaning is stored in two ways:

  1. Superset Relationships: Links between a node and its category (e.g., "A Canary is a Bird").

  2. Property Relationships: Links between a node and its features (e.g., "A Canary can sing" or "A Bird has wings").

• Assumption (Cognitive Economy): Properties are stored only once at the highest possible level (most general node) to avoid redundancy. For example, "has skin" is stored at "Animal," not at "Canary" and "Shark."

Hierarchical Network Model Testing and Findings 

• Method: The Sentence Verification Task. Participants see simple sentences (e.g., "A canary can sing," "A canary has skin") and must quickly press a "True" or "False" button. Their Reaction Time (RT) is measured.

• Mechanism (Spreading Activation): When a concept (like "canary") is presented, its node activates and this activation spreads to connected nodes. To verify "A canary has skin," the activation must spread from "canary" to "bird" to "animal" and find "has skin."

• Findings: RT was a function of the distance between nodes.

  • (P0) "A canary can sing" was fastest (0 levels).

  • (P1) "A canary can fly" was slower (1 level).

  • (P2) "A canary has skin" was slowest (2 levels). This supported the hierarchical structure.

Problems w Hierarchical Network Model

The model could not explain two key findings:

1. Typicality Effects: People are faster to verify typical examples of a category than atypical ones (e.g., "A robin is a bird" is verified faster than "A penguin is a bird"), even though the distance in the hierarchy is the same (1 level).

2. Category Size Effects: People are faster to verify "A dog is a mammal" than "A dog is an animal," even though "mammal" is a lower (more specific) category, and "animal" should be closer.

Parallel Distributed Processing/Connectionists Models of Memory

• PDP models are inspired by the brain's neural networks. They consist of a large set of simple, interconnected processing nodes (~neurons).

• How Memories are Stored: Memories are not stored in a single node. A memory (or concept) is a specific pattern of activation distributed across the entire network. The "knowledge" is stored in the connection weights (strengths) between nodes, which are adjusted through learning.

• How They Work: When an input is presented (e.S., "Robin"), it activates a set of input nodes, which then spreads activation through the network to create a pattern on the output nodes (e.g., "can fly," "has wings").

• Pro/Con: They are very good at generalization (a new example like "kookaburra" can "inherit" properties of other birds). They are bad at learning atypical examples/exceptions (like "penguin").

Bartlett’s War of Ghosts Experiment

• Experiment: Bartlett had British participants read a complex and culturally unfamiliar Native American folk tale ("War of the Ghosts"). He then used serial reproduction—having one person retell the story from memory, then a second person retell their version, and so on.

• Findings: The story became progressively shorter, more coherent, and more conventional. Bartlett observed specific transformations as participants' schemas distorted the memory:

  • Omissions: Unfamiliar details (like "something black came out of his mouth") were dropped.

  • Normalization: Unfamiliar concepts were changed to familiar ones (e.g., "canoe" became "boat," "hunting seals" became "fishing").

  • Rationalization: The story was altered to make more sense from a British cultural perspective (e.g., justifying why the man died).

• Conclusion: This led Bartlett to propose that memory is not a perfect recording but a reconstructive process guided by our pre-existing mental structures, which he called schemas.

Schema Defintion

• A schema is a generalized mental representation or concept that organizes our knowledge about a class of objects, people, scenes, or events. It's a mental "framework" or "blueprint."

• Benefits (Memory Economy): Schemas make memory encoding more efficient. They tell us what to expect and what to pay attention to, so we don't have to process every detail (e.g., you don't need to encode "has chairs" and "has tables" when you enter a lecture theatre; your "lecture schema" fills that in).

• Drawbacks (Errors): Schemas can lead to systematic distortions, omissions, and false inclusions. We may "remember" things that didn't happen simply because they are part of the schema (e.g., falsely recalling seeing books in an office).

Person Schemas (Stereotype)

• Definition: A schema about the attributes and behaviors of a type of person.

• Example: Stereotypes. These can be based on profession (a "Tesla driver"), gender, or race. These schemas create expectations and can lead to bias (e.g., the "Arabs as Terrorists" stereotype in video games).

Event Schema (Script)

• Definition: A schema for the typical sequence of events that occurs in a common situation.

• Example: A "restaurant script" (enter, wait to be seated, get menu, order, eat, pay, leave) or a "birthday party script" (guests arrive, give presents, play games, eat cake, sing 'Happy Birthday').

Script Transference (Misapplication of a Script) 

• Definition: This is an error that occurs when you inappropriately apply a script from one situation to a new, different situation, leading to failure and poor coping.

• Example: Applying the "High School Script" to the "University Script."

  • HS Script: "Wait for the teacher to tell me what to do and when to do it. The main goal is to pass exams."

  • Uni Script (Required): "I must proactively find requirements, set my own deadlines, plan my time, and self-guide my learning."

  • Misapplication: A uni student who waits to be told what to do will miss deadlines, fail to do voluntary readings, and not understand the material, all because they are using the wrong mental "blueprint" for the situation.