HumanHurriyatul Fitriyah [hfitriyah@ub.ac.id]

Human – Computer Interaction Course

Computer System - Information Technology & Computer Science Program

1. Introduction

Human Information Processing

This lecture focused on human information processing that includes:

1. Perceiving2. Memorising3. Processing

Human are limited to their capacity to process information. This has important implication for design

2. Human Perceptor

Human’s

Information is received via a number of human sensory channel:

1. Visual channel

2. Auditory channel

3. Haptic channel

Plus one additional input channel:

4. Movement

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4 Input channelsfor Computer Interface

1. Visual Channel

We see windows, buttons, numbers, alphabets, lights -colours, menus, icons in our computer –machine

We design our computer system by adapting the way the eye perceive brightness, colour, size, depth and relative distance

Visual Perception

1. Size, Depth & Relative Distance

• Human still can identify objects, even in various size (law of constancy)

2. Brightness• Brigthness is subjective reaction to

level of lights• Brighness perception is subject to

luminance (the amount of light emiited by an object)

3. Colour• colour component: hue (wavelength

of light), intensity (brightness), saturation (amount of whiteness)

• Cones photoreceptors has three type that each is sensitive to different colour (blu, green, red)

Reading

Reading process stages: 1. Perceiving visual pattern on the word on the page2. Decoding the pattern with reference to an internal

representation of language3. Syntatic and semantic analysing and operate on

phrases or sentence

During reading, eyes do saccades followed by fixations, also regressions (move backwards and forwards over text)

Words are not recognised character by character, but by word shape

Experiment suggest standard font size for legible reading is 9 to 12 points

Negative contrast (dark character on a light screen) provides higher luminance, therefor increase acuity

What can we learn and use from visual perception to our computer design?

Design Example

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2. Auditory Channel

Sound (non-speech) is used as an addition to visual computer-communication

1. Attention

2. Status information

3. Confirmation

4. Navigation

Sound is also used for visual impaired communcation aid

3. Haptic Channel

Touch screen is explored because people dislike to be troubled with mouse (and it’s more way cool isn’t it?)

Vibration, give feedback (information, alert) when user don’t want to use visual and sound

Haptic application in computer gaming

Now we seek a technology that allow user to feel surface (texture) and shape such for e-commerce application

4. Movement

Speed and accuracy of movement is important in computer design primarily to hit a target on a screen

The time taken to hit a target = a + b log2 (distance/ size + 1), where a & b is empirically determined constants

Movement in gaming application:

To direct the input

3. Human Memory

Information is stored in memory

1. Sensory memory

2. Short-term (working) memory

3. Long-term memory

1. Sensory memory

There are 3 sensory memory:

1. Iconic memory for visual stimuli

2. Echoic memory for aural stimuli

3. Haptic memory for touch stimuli

It’s constantly overwritten by new information coming

Example: moving fingers in front of eyes, seeing firework

2. Short-term Memory

Working as ‘scratch-pad’ for temporary recall

Example: during multiplication like in 35x6

Example of human STM adapted in computer design:

Early automatic teller machines (ATMs) gave the customer money before returning their bank card. On receiving the money the customer would reach closure and hence often forget to take the card. Modern ATMs return the card first!

3. Long-term Memory

It’s our main memory, here we store factual information, experimental knowledge, procedural rules of behaviour, everything we know

2 type of long-term memory:1. Episodic memory for events and experience2. Semantic memory for facts, concept and

acquired skill

Security: arch enemy of memory

Imagine we have to memorise all important number and code, such: postal code, phone number, password

Now it has to be alphanumerical (plus symbol)

Now it has to be more than 6 numbers

The worst of all: we have to keep them secret, in mind. It can’t be written!

Network engineers suggest us what they called a solution for this: nonsense password but still meaningfull to user (eg. Initial of names, number of significant dates)

3. Human ThinkReasoning and Problem Solving

Information is prosessed and applied:• Reasoning• Problem solving• Skill acquisition• error

3.1. Reasoning

Reasoning is a means of inferring new information from what is already known

1. Deductive: derive conclusion from given premise/s Example: It is FRIDAY then he WILL GO TO WORK

2. Inductive: generalising from case we have seen to infer information about cases we have not seen Example: we have seen several elephant have trunks,

we conclude that all elephant have trunks It’s unreliable, but usefull for constanlty learning new

environment

3. Abductive: it reason from a fact to the action or state that caused it Problem in interactive system: if an event always follow

an action, the user will infere that the event is caused by the action

3.2. Problem Solving

Problem solving is process of finding solution to an unfamiliar task, using the knowledge we have

There are 3 main theory how human solve problem1. Gestalt theory: problem solving is a matter of

reproducing known response or trial and error2. Problem soace theory: problem has initial state and a

goal state and people use the operator from the former to later

3. Analogy in problem solving: people use current knowledge as an analogy to solve novel problem

3.3. Skill Acquisition

Three basic level of skills:1. The real uses general-purpose rules which interpret

facts about a problem. This is slow and demanding on memory access

2. The learner develops rules spesific to the task3. The rules are tuned to speed up performance

Example of skill acquisition

Imagine you are learning to cook. Initially, you may have general rule to tell you how long a dish needs to be in the oven

proceduralization

Gradually your knowledge becomes proceduralized and you have specific rules for each case

Generalization

Finally, you may generalize from these rules to produce general-purpose rules

The difference between Human & Computer

Example: chess play

3.4. Error

Some error are trivial, some maybe serious and requiring subtansial effort to correct

If a pattern of behaviour has become automatic and we change some aspect of it, the familiar pattern may break throught and becomes error

Others is from incorrect understanding (mental models)

The mental models might be a partia incorrect understanding, or internally inconsistent

4. Human Emotion

Emotion influences human capabilities

It suggest that in situation of stress, people will be less able to cope with complek problem solving or managing difficult interface.

5. Individual Difference

Users share common capabilities but are individuals with differences, which should not be ignored

Difference including sex, physical capabilities and intellectual capabilities