Chapter 3 – Human Information Processing

HCI: Designing Effective Organizational Information Systems

Dov Te’eniJane Carey

Chapter 3 – Human Information Processing

Designing effective Human-Computer Interaction depends on understanding how humans process information Key aspects of Chapter 3:– HIP model– Performance is a function of speed and accuracy– Context

Chapter 3 - HIP

Consider the task of editing a file using a computer which involves:– Controlled processing (versus automatic) – Goal-driven behavior (versus random)

Relationship between Controlled processes and goal-driven behavior– Example: trying to catch another driver while staying

below the speed limit

Figure 3.1 Objectives and Actions in Preparing a Word Processing Document

Print FileDetermine

LayoutSave FileSetup FileObjectives

ActionsOpen Document Name the File

Set top/bottom Margins

Set Left/RightMargins

Set Print Options

Steps in preparing a word-processed document Step 1. Open a new file

Step 2. Assign a nameStep 3. Set marginsStep 4. Set printer optionsStep 5. Type textStep 6. Insert figuresStep 7. Edit text Step 8. Add cover pageStep 9. Spell checkStep 10. Change fontStep 11. Repeat until satisfiedStep 12. PrintStep 13. Save file

This task is difficult to turn into an automatic process due to complexity and sub-goals and therefore will remain a controlled process.

Chapter 3. HIP

What are the implications for design?– If a task is goal-driven and requires fast

performance, the designer should guide the user with a sequence of actions that build toward the goal

– In the case of the word processor, some default parameters can be set to minimize the work on the part of the user which in turn speeds up the task

– Knowledge of HIP allows a designer to draw design implications

Chapter 3 - HIP

This book will draw on several cognitive models including:GOMS (Goals, Operators, Methods, Selection Rules) by Card, Moran, NewellA rough model of Human Information Processing (HIP)– Stages of IP

• Sensation• Perception• Decision• Response Execution

Chapter 3 – HIP

The HIP view of the user– An information system that accepts inputs from the

external world and produces responses directed out to the external world

Inputs Outputs

Chapter 3 - HIP

Figure 3.2 Stages of Information Processing

Stages of HIP

Memory(Attention) Processors

Working Memory

Long-termMemory

Perception Cognition Motor

Touch/FeelingIdentification

Location

TranslationOperationDecision

Translation toAction

(Keyboard, Mouse)

Chapter 3 - HIP

Figure 3.2 ExplanationThe perceptual processor senses, detects, and accepts inputs from the external world and stores parts of the perceptions in working memory (these are visual or auditory)The cognitive processor interprets, manipulates, and makes decisions about the inputs (along with memory)The motor processor generates physical actions (such as keying and mouse clicking) based on perceptions and cognitions

Chapter 3 - HIPFigure 3.2 Explained (cont.)– All these parts interact with each other– The idea of performance (speed and accuracy) is

introduced– HCI Designers try to implement designs that make

the interface usable and increase performance– Some constraints

• Working memory capacity is 7+ 2 chunks for 10-20 seconds

• Cycle time of processors around 100 milliseconds (with motor being the slowest)

• Long-term memory capacity is almost unlimited, but difficult to retrieve from

Chapter 3 - HIP

Design implications– User will not notice screen changes within screen changes– User perception is limited to 7+ 2 chunks of information and will

ignore part of the screen– Long-term memory retrieval will significantly degrade

performance– Designs must reflect these issues

Additional impacts include: motivation to use, practice, and attributes of representation (such as intensity)

Chapter 3 - HIP

Perceptual Processor– Works tightly with perceptual storage– 3 principles of relevance

• Input buffers of the working memory store visual and auditory images

• Perceptual processor works in cycles (pulses combined to make 1 signal)

• More intense signals require less time to process

Chapter 3 - HIP

Cognitive Processor– Cognitive processors are automatic (fast and

undemanding) or controlled (slower and demanding)– Cognitive Processors can process both images and

verbal (text) information (but differently)– Cognitive processing is not always consistent over

time and is content-related

3.4 Watson and Johnson-Laird (1966) Logical Reasoning Experiment

$10 $30 No signature

E K 4 7

Signature

Chapter 3 - HIP

Cognitive processing is not uniform and depends on:– Task requirements – User familiarity with task (automatic or controlled)– Type of information (verbal or image)– Heuristics

Chapter 3 - HIP

Memory and Processing– The role of memory is critical and must be examined– Working memory

• Limited capacity and retention time• Stores both images and verbal information (text)• Task complexity is related to forgetting and interference• Order is important in verbal storage• Rehearsal can increase remembrance

– Working memory interacts with long-term memory

Chapter 3 - HIP

Long-term memory– Is episodic(direct memory) or semantic(meanings)– Individual differences come into play (age for

example, can negatively impact memory capacity)Organizing Memory– Schemata (high order cognitive structures such as

scripts)– Metaphors (related to an already familiar concept,

e.g., desk top as a metaphor for RAM)

Chapter 3 - HIP

More organizing mechanisms– Mental model – mental representation– Heuristics – short cuts or rules of thumb (e.g., boys

are more athletic than girls is a judgment by representativeness and may lead to erroneous conclusions)

Chapter 3 - HIP

Principles of HIP and Memory– Different combinations of tasks and memory will

trigger different cognitive processors– In simple tasks, performance (accuracy and speed)

depends on heuristic processes and episodes– Complex tasks can use schemata (mental models,

heuristics, metaphors) to increase performance– Unfamiliar tasks require the creation of new

schemata which in turn slows down the performance

Chapter 3 - HIPMore principles– Heuristics is based on the salient (meaningful) task features

• If the salient features provide a clear task structure then performance will be improved

• Use familiar labels on screens

HIP in context– Context is essential to comprehension– Immediate context (what user was doing before looking at the

current screen– Distant context (in which the task occurs (like choosing the

right investment portfolio)

Chapter 3 - HIP

Guiding principles of context– Context must be maintained during an interactive

session– Stick with one mental model or metaphor– Continuity between screens helps maintain context- Figure 3.5 shows the Block Interaction Model of

Morton, Barnard, and Hammond (1979) and helps explain how different sources of knowledge interact to affect the context of work

Figure 3.5 Block Interaction Model byMorton, Banner, & Hammond, 1979

Knowledge of the context

Knowledge of the Context bound to the system

Knowledge of the actions of the system

Knowledge of the Version

Knowledge of theProblem

Knowledge of the domain

Knowledge of the computer(documentation,

software,hardware)

Knowledge of the Natural Language

Knowledge of the process, problem-solving and mechanism

Chapter 3 - HIP

Coding and Retrieving– Coding (prior to storage)– Retrieval (from memory)– Observations

• The more active you are in generating information items, the better your recall

• Pictures are easier to recall than words• Recall “in context” is easier than “out of context”• Complex patterns are more difficult to recall than simple• Clues stored at the time of coding make recall easier• Aging reduces memory capacity

Chapter 3 - HIP

Conclusions– Models help our understanding of HIP (– Performance is a function of cognitive management,

memory, processing, attention, and comprehension– Performance is speed and accuracy– We can use schemata to organize knowledge

(mental models, metaphors, heuristics)– Comprehension is sensitive to context