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Memory

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A little experiment in memory …

Courtesy of NASA Ames Cognition Laboratory (http://human-factors.arc.nasa.gov/cognition/tutorials/ModelOf/memory5.html)

Step 1: take out a blank sheet of paper and put “List 1” on the top. Then put your pencil/pen down.

Step 2: listen to the list of words carefully. Step 3: after the entire list is finished, you will be instructed

to write down as many of the words as you can remember. Step 4: check your list against the one I show you and write

the number correct at the top of the page. Repeat steps 1 – 4 with List 2 and List 3.

Watch the YouTube video. After it is finished, write down as many words and images from the video as you remember.

(https://www.youtube.com/watch?v=xLd22ha_-VU)

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Results from an earlier experiment

http://human-factors.arc.nasa.gov/cognition/tutorials/ModelOf/memory5.html

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Impact of memory on system design ...

Power: Vast store of knowledge

Limitations: Forgetting Limited working memory Attention

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“Just the facts” about memory ...

Three subsystems of memory: Short-term sensory store Working memory (short-term memory) – WM/STM Long-term memory - LTM

These subsystems differ in several ways Capacity

Sensory store __________________________________

WM is ______________________________• (the "magic number" 7 plus or minus 2)

LTM __________________________

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“Just the facts” about memory … (cont.)

Differences in memory subsystems (cont.) Duration

Sensory store _____________________________________

WM _____________________________________________

LTM _____________________________ Codes

Sensory store ____________________

WM ____________________________

LTM ____________________________

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How it works (or doesn’t) ...

Working Memory (WM) A model (from Baddeley)

Central

Executive

Phonological LoopVisuospatial Sketchpad

• Stored in analog spatial form

• From visual sensory system or LTM

• Stored in acoustical form

• Info kept active through rehearsal

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WM: How it works (or doesn’t) ... Restrictions:

Capacity - 7 + 2 “items” of information. Time - 30 seconds to 2 minutes

Some solutions ... Increase capacity by “chunking”

Create meaningful sequence already present in LTM Experiments:

– Subject could recall > 20 binary digits by coding into octal (0101111 57)

– Subject could recall > 80 digits by coding into running times (353431653 3 min, 53.4 sec mile; 3 hr, 16 min, 53 sec marathon)

– Chess masters recall board with great accuracy; "chunk" into strategic patterns

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WM: How it works (or doesn’t) ... Examples of everyday chunking:

Parsing - break up into chunks phone numbers, social security numbers

Reading musical staffs ("Every Good Boy Does Fine") Medical school mnemonics Songs: constraints of rhythm, rhyme

"We Didn't Start the Fire"

"Joseph and the Amazing Technicolor Dreamcoat"

Preamble to the US Constitution

Other approaches to handling WM limitations: Minimize load Visual “echoes” Exploit different codes (e.g., spatial, verbal, etc.)

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Primacy and Recency

Items that appear early in a list are the easiest to recall.

The last items are also easier than the ones in middle if recall if the recall delay is less than 30 seconds.

Anchoring effect – essentially a primacy effect where the operator is so busy trying to process an early item that he misses the subsequent items.

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Interference

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Working Memory

STM Recall of rules in cognitive process Executive function and attention Hierarchically organized

Domain-specific workspace(s) Executive function Fluid intelligence

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Task Switching

Alleviates fatigue Switching cost on WM, especially from

unwanted interruptions Type of discretionary switching strategies

Task first – complete all of one type before moving on to another

Set first – do a complete set of (sub)tasks then repeat Mixed strategies Random

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How it works (or doesn’t) ... Long-term memory (LTM)

Types Semantic memory - general knowledge Event memory

Episodic - an event in the past Prospective - remember to do something

Basic mechanisms: Storage - through active rehearsal, involvement, or link to an

existing memory. Alternatively - “everything gets in”

Retrieval - depends on item strength number and strength of associations to other items

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Hypothetical Association Structure in the LTM

Retrieval cue triggers black dot. Black dot activates pink ones near by.

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LTM: How it works (or doesn’t) ...

Organization of information in LTM Most-used information is semantic

retrieval depends on semantic associations good design builds / uses appropriate semantic associations

The network of semantic associations around specific topics are schemas

Schemas involving sequences of activities are scripts Schemas concerning how equipment and systems work are

mental models

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LTM: How it works (or doesn’t) ...

What it means for design … Encourage regular use of info Standardize Design information to be remembered Provide memory aids

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Types of Memory Encoding Semantic -- meaning of words Propositional -- underlying relationships among

concepts, not always distinguishable from spatial encoding

Visual-spatial – recall map of Bora Bora with 6 landmarks

Episodic memory -- events and the effect of emotion.

Procedural memory -- how to do something.

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Memory versus knowledge “in the world”

When do you not need to remember something? (Why do you not need to remember what a penny

looks like?)

When the knowledge is already "in the world"! (Because you only need to recognize a penny - and

nothing else looks like it.)

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Knowledge “in the world”

Affordances Constraints Mappings Conceptual Models Visible Structure

Reveals:– 1. affordances– 2. constraints– 3. mappings

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Affordance

"refers to perceived or actual properties of the thing, primarily those fundamental properties that determine just how the thing could possibly be used.” (Norman, The Design of Everyday Things, pg. 9)

Affordances of objects: e.g., chairs, tables, cups

Affordances of materials: e.g., glass, wood

Affordances of controls: How are things operated?

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Examples ...

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Constraints

Those aspects of a device or material that limit its perceived possible uses.

Physical: size, shape, possibilities for movement, etc.

Semantic: meaning of the situation related to the notion of “conceptual models”

Cultural: defined by tradition, meaning within the culture (e.g., the color red, triangular shape)

Logical: placement of controls, direction of movement, etc.

related to “mappings”

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Examples ...

Physical constraints

Semantic constraints

Cultural constraints

Logical constraints

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Conceptual Models

Our understanding of the way things work, how things are put together, cause & effect, etc. Depends on the visibility of the system structure, the

timing of the feedback, and consistency of cause/effect relationships

Builds a framework for storing knowledge about a system or device “in the head.”

Used to develop explanations, recreate forgotten knowledge, and make predictions.

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Mappings Making the connection between how things work

and how we think they work. Some examples … (recall the display design lesson!)

– Principle of Pictorial Realism: Displayed quantities should correspond to the human's internal model of these quantities.

– Congruence: The linear motion of a control and display should be along the same axis and the rotational motion of a control and display should be in the same direction.

– Principle of the Moving Part: The direction of movement of an indicator on a display should be compatible with the direction of movement of an operator's internal representation of the variable whose change is indicated.

– Spatial compatibility: The spatial arrangement of displays should be preserved in the controls.