1 ISE 412 Memory LONG-TERM MEMORY WORKING MEMORY SENSORY STORE

2 ISE 412 A little experiment in memory … Courtesy of NASA Ames Cognition Laboratory ( 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.

3 ISE 412 Results from an earlier experiment

4 ISE 412 Impact of memory on system design... Power:  Vast store of knowledge Limitations:  Forgetting  Limited working memory  Attention

5 ISE 412 “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 __________________________

6 ISE 412 “Just the facts” about memory … (cont.) Differences in memory subsystems (cont.)  Duration Sensory store _____________________________________ WM _____________________________________________ LTM _____________________________  Codes Sensory store ____________________ WM ____________________________ LTM ____________________________

7 ISE 412 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

8 ISE 412 WM: How it works (or doesn’t)... Restrictions:  Capacity “items” of information.  Time second “half-life” Some solutions...  Increase capacity by “chunking” Create meaningful sequence already present in LTM Experiments: – Subject could recall > 20 binary digits by coding into octal (  57) – Subject could recall > 80 digits by coding into running times (  3 min, 53.4 sec mile; 3 hr, 16 min, 53 sec marathon) – Chess masters recall board with great accuracy; "chunk" into strategic patterns

9 ISE 412 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

10 ISE 412 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

11 ISE 412 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

12 ISE 412 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

13 ISE 412 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.)

14 ISE 412 Knowledge “in the world” from Norman, D.A. The Design of Everyday Things, (formerly "P.O.E.T.") New York: Currency/ Doubleday.) Affordances Constraints Mappings Conceptual Models Visible Structure  Reveals: – 1. affordances – 2. constraints – 3. mappings

15 ISE 412 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, pg. 9)  Affordances of objects: e.g., chairs, tables, cups  Affordances of materials: e.g., glass, wood  Affordances of controls: How are things operated?

16 ISE 412 Examples...

17 ISE 412 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”

18 ISE 412 Examples... Physical constraints Semantic constraints Cultural constraints Logical constraints

19 ISE 412 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.

20 ISE 412 Mappings Making the connection between how things work and how we think they work.  Some examples … (stay tuned - more in 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.

21 ISE 412 Your turn … Recall the question regarding Benjamin Franklin given to you as homework last week. 1.List a few of the things you’ve thought of that Mr. Franklin would be able to “figure out” in your apartment/home. 2.Describe how Mr. Franklin is able to figure these things out in terms of the affordances, constraints, mappings, and visible structure. Use the following table to help organize your answer.

22 ISE 412 What Mr. Franklin can figure out Affordances Physical Constraints Semantic Constraints Logical Constraints Cultural Constraints

23 ISE 412 ATTENTION!!! From page 147 of Wickens et al. ATTENTION RESOURCES

24 ISE 412 ATTENTION!!! A "flexible, sharable, processing resource of limited availability". Our ability to attend to several things at once (time-sharing) depends on:  Controlled vs automatic processing  Skill  Which resource(s) required Attention “tasks” can be divided into 4 categories...

25 ISE Selective Attention "requires the monitoring of several channels (sources) of information to perform a single task.”  Example: scanning cockpit instruments Limitations: – As the number of channels of information increases, performance declines (even when the overall signal rate is the same). – Can select inappropriate aspect(s) of the environment to process. – "Cognitive tunnel vision" in complex environments with many displays, especially under stress. (Example: 1972 Eastern Airlines crash in the Everglades). Errors associated with Selective Attention are generally the result of an intentional, but unwise choice.

26 ISE 412 Selective Attention Design Guidelines:  Place frequently sampled displays together.  Place sequentially sampled displays together.  Use external aids/reminders to help people remember when the display was last sampled.

27 ISE Focused Attention Requires attending to one source of information at the exclusion of all others  Examples: Trying to study while someone else is talking on the phone Trying to enter numerical data into Excel while others are discussing basketball scores and stats. Limitations:  Impossible to ignore a visual stimulus within 1 degree of visual angle of the visual information you are interested in.  Auditory stimuli sufficiently loud with respect to the signal you are interested in, and/or similar to it, can interfere with the signal. Errors associated with focused attention are generally unintentional, driven by the environment.

28 ISE 412 Focused Attention Design Guidelines: Parallel vs serial processing  Parallel processing is helpful when: two tightly coupled tasks are performed simultaneously (e.g., control roll and pitch of aircraft) two or more information sources imply common action (redundancy gain)  Parallel processing is harmful when similar aspects of different stimuli must be processed (resource competition) two or more stimuli imply different actions e.g., a batter distracted by a moth

29 ISE Sustained Attention "the ability of observers to maintain attention and remain alert over prolonged periods of time."  Example: Security guard watching monitor for intruders. Limitations:  Vigilance decrement - a decline in the speed and accuracy of signal detection with time on the task (found more in the laboratory than in real world tasks).

30 ISE 412 Sustained Attention Design Guidelines:  Appropriate work-rest schedules and task variation.  Increase the conspicuity of the signal.  Reduce uncertainty as to when and where.  Training.

31 ISE Divided Attention "two or more separate tasks must be performed at the same time, and attention must be paid to both.”  Example: Driving and talking to a passenger. Limitations:  Time-sharing...

32 ISE 412 The Resource Metaphor of Attention Time-sharing (or doing two tasks simultaneously) is difficult because we have limited attention resources. The Performance-Resource Function (PRF)

33 ISE 412 The Performance Operating Characteristic (POC) Performance Operating Characteristic Curve Task A Task B

34 ISE 412 Limitations of the "Single-Resource" Theory of Attention Difficulty insensitivity  In some experiments it has been shown that making one time- shared task more difficult has no effect on the performance of the other. Perfect time-sharing Structural alteration effects  In some experiments it has been shown that altering the structure (but NOT the difficulty) of one task affects performance on the other.  Example: Manual vs vocal responses to a tone discrimination task while tracking.

35 ISE 412 Multiple-Resource Theory Instead of one "pool" of resources, there are several different capacities of resources:  Codes: spatial or verbal  Modalities: visual or auditory  Stages of processing: early (encoding/central processing) or late (responding) The more resources are shared, the more tasks will interfere.

36 ISE 412 Multiple-Resource Theory To the extent that tasks demand separate rather than common resources:  Time-sharing will be more efficient  Difficulty insensitivity will be observed  The POC will be more "boxy"

37 ISE 412 Limitation of Multiple Resource Theory The three proposed dimensions (stages, codes, modalities) do not account for all experimental findings. For example:  Tasks with different rhythmic requirements are hard to time-share.  Control dynamics affect the efficiency of time-sharing a manual tracking task with another task.

38 ISE 412 Implications & Design Recommendations Since spatial and verbal codes draw upon separate resources, time-sharing manual and verbal responses is highly efficient (assuming that the manual response is spatial in nature and that the vocal response is verbal). Example: pilots fly the airplane (spatial, manual task) and simultaneously talk to air traffic control (verbal, vocal task). This example also demonstrates different modalities (visual and auditory) which also draw from separate resources; therefore … Design systems to support a mix of manual and vocal responses for time-shared tasks.

39 ISE 412 Multiple Resource Theory The effect of training  Training can make tasks data limited rather than resource limited Data limited tasks can coexist more easily than resource- limited Reasoning behind “part-task training” paradigms  People can also be trained to timeshare tasks more efficiently Rapid switching between tasks True multi-tasking