Lecture 12 – Comprehension 1

In Chapter 9, we looked at how concepts are mentally represented and accessed.

• General forms are used• most likely to be useful in the future• detail stripped away• at the scale of the word or schema

Chapter 11 is about how we generate knowledge at a larger scale – for example, the scale of texts.

Introduction

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The Challenge

To understand the challenge of acquiring a text, think about how we acquire concepts in childhood.

• through repetition and successive refinement

• e.g, doggie – first, all four-legged animals, then, small four-legged animals, then dogs.

• as children, we have years to accomplish this

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Reading a text, we go through the same process in a much shorter time – perhaps minutes.

‘Reading a text’ may mean reading words written on a page or reading a situation.

• E.g., how have American leaders ‘read’ the situation in Afghanistan?

The Challenge

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Three influences on text comprehension

The task is to read and remember a text-level message. What influences our ability to encode, store, and retrieve larger units of meaning?

• The reader’s knowledge

• The structure of the text

• The interaction of these two

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1. The reader’s knowledge

2. The structure of the text

3. The interaction of these two

Three influences on text comprehension

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The Reader’s Knowledge

Q. What kind of knowledge influences comprehension?

A. Schema knowledge

Q. What do schemas influence?

A. Schemas have effects at both encoding, and retrieval.

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Bransford & Johnson (1973)

• balloon serenade passage

No context group remembered 3.6 propsnsContext after group remembered 3.6 “Context before group remembered 8.0 “

Point: you can’t remember what you don’t comprehend.

Schema effects at encoding

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Schema effects on retrieval

Dooling & Christianson (1973)

Read this passage:

Carol Harris was a problem child from birth. She was wild, stubborn, and violent. By the time Carol turned eight, she was still unmanageable. Her parents were very concerned about her mental health. There was no good institution in her state. Her parents finally decided to take some action. They hired a private teacher for Carol.

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Dooling & Christianson (1973)

Dooling & Christianson showed 2 groups of subjects that passage, and one week later, asked them to say whether the following sentence appeared in the passage:

“She was deaf, dumb, and blind.”

One group of subjects got no further information. One group was told, just before recall, that the story was really about Helen Keller.

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Dooling & Christianson’s results

Very few people in the control group said ‘Yes.’

Many people in the experimental group (told the story was about Helen Keller) said ‘Yes.’

For experimental group, retrieval process was influenced by their world knowledge, including knowledge of who Helen Keller was.

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Schema effects – conclusions

Bransford & Johnson:

• without schema, passage was difficult to understand and encode. Here, schema made memory performance more accurate.

Dooling & Christianson:

• passage easy to comprehend without schema. Schema produced a retrieval error.

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Schema effects – conclusions

Schemas can have either positive or negative effects at both encoding and retrieval.

If what you’re seeing or recalling is schema-consistent, the schema will help.

If what you’re seeing or recalling is schema-inconsistent, the schema will hinder.

Which is more likely?

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1. The reader’s knowledge

2. The structure of the text

3. The interaction of these two

Three influences on text comprehension

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The structure of the text

Comprehension and memory are affected by:

1. A story’s global structure.

2. A story’s local detail.

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Global structure vs. local detail

Consider Shakespeare’s Romeo & Juliet, and Bernstein’s West Side Story.

Global structure (very briefly):

• feuding social groups• young lovers from opposing sides• their love overwhelms reason• dire results

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Global structure vs. local detail

Romeo & Juliet vs. West Side Story

Local detail:

R&J WSS

Capulets & Montagues Jets & Sharks (gangs)16th century Europe 20th century USAHorses, swords Cars, guns

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Global structure vs. local detail

Both global structure and local detail influence comprehension.

• Changing global structure may impair comprehension – consider the movie Memento. You don’t have theme, or plot to work with.

• Aspects of local detail may also affect how easily a text is understood and how well it is remembered.

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Effects of Global Structure

Thorndyke (1975)

• Developed a grammar of story-telling.

• Story structure is hierarchical.

• Hierarchy can be thought of as a relation of containment, as in original network theory.

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Effects of Global Structure

Sentence NP + VP

Noun phrase (Det) + (Adj) + Noun

Verb phrase (Aux) + (Adv) + Verb

These relations can be represented in a network structure, as on the next slide. The network tells us about the structure of the sentence/text

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Sentence  

Noun Phrase Verb Phrase  

Determiner Adjective Noun Verb Adverb

 The good student read happily 

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Thorndyke’s grammar of storytelling

Thorndyke argued that stories have structure.

Stories consist of a setting, a theme, a plot, and a resolution.

Each of these components contains sub-components, just as a sentence contains phrases that in turn contain words.

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Thorndyke’s Grammar of Story-telling

Setting characters + location + time

Theme event + a goal

Plot episodes

Resolution subgoal + attempt + outcome

Manipulating story structure influences both comprehension and memory performance.

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Effects of Local Structure

The points to be made here are

• local structure is built out of propositions

• building that local structure involves two processes:

• referring a comment back to a topic within a proposition.• building bridges between propositions.

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Effects of Local Detail

When you read a passage, you interpret and store the passage as a structured set of propositions.

Proposition: the smallest unit of meaning that can have a truth-value (that is, can be true or false).

E.g. Dog – no sense in which this can be true or false.

The dog is blue – this can be true or false.

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Building structure out of propositions

Doing this involves two demanding processes:

1. Referring a comment back to a topic

The dog I saw that lady with the flowered hat walking yesterday was a spaniel.

The more propositions appear between topic and comment, the tougher comprehension is.

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2. Building bridges between two ideas.

John threw a cigarette out of his window while driving through the forest. The fire destroyed hundreds of acres.

The reader must add: The cigarette caused the fire.

This is an implicit proposition. Comprehension is easier if bridging propositions are explicit.

Building structure out of propositions

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Building structure out of propositions - evidence

1. Haviland & Clark (1974)

a. Horace got some beer out of the trunk. The beer was warm.

b. Horace was especially fond of beer. The beer was warm.

Task: press button when you comprehend second sentence.

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Haviland & Clark

Result:

People took longer in condition b. than in condition a.

Conclusion:

Extra time was necessary to make the bridge – to work out that the beer in the second sentence was related to the beer in the first sentence.

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Building structure out of propositions - evidence

Kintsch (1974)

Gave subjects sentences like the one about John and the fire above. Tested their memory for the passages either immediately after reading or 20 minutes later.

Immediate: Memory better for explicit propositions.

Later: Memory equal for two kinds.

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Kintsch

Conclusion:

Successful integration of new information into the developing text structure means that surface form of text (the actual words) can be discarded.

What is retained in memory is the propositional structure. In that representation, implicit and explicit propositions are equal.

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1. The reader’s knowledge

2. The structure of the text

3. The interaction of these two

Three influences on text comprehension

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Integrating the reader’s knowledge and the text

The dominant figure in this area is Walter Kintsch.

Van Dijk & Kintsch (1978) argued for three different levels of representation of texts:

• Surface code• Textbase• Situation model

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Van Dijk & Kintsch’s model

• The surface code represents a text using the actual words in the text.

• A textbase represents a text in the form of propositions (explicit and implicit).

• A situation model is a mental model that integrates the text information with pre-existing world-knowledge (also in proposition form).

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SurfaceCode

The text

SituationModel

Knowledge about the world

Textbase

Knowledge about the text

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Van Dijk & Kintsch’s model

As propositions are extracted from the text:

• they are organized around the structure the reader expects (setting, conflict, etc.)

• missing parts can be filled in from semantic memory

• parts not relevant to reader’s goals can be deleted.

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Van Dijk & Kintsch’s model

Review:

Comprehension is an active process.

Propositions are extracted from surface code (explicit) or inferred (implicit), then organized.

Propositions are organized around expected text structure, and in concert with reader’s goals.