1 the user lecture 2 date: 2 nd february ‘05. 2 overview of lecture introduce human considerations...

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The User

Lecture 2Date: 2nd February ‘05

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Overview of Lecture

•Introduce human considerations in

developing a user interfaces

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The User

The user is the most important entity of the system

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The User

The User

Nature of User

Human Considerations

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Nature of User

Nature of User

User User GroupsGroups

Computer skillsComputer skills& knowledge& knowledge

Age Age

DisabilitiesDisabilities CulturalCultural

Reminder - Reminder -

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The User

The User

Nature of User

Human Human ConsiderationsConsiderations

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•A vital foundation for HCI designers is an understanding of cognitive and perceptual abilities of the user

•Cognition is what goes on in our heads when we carry out everyday activities

•There are numerous cognitive frameworks each having different perspectives on cognition

•It involves cognitive processes such as perception, attention, memory and learning


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Cognitive Frameworks

•Cognitive frameworks help us to understand how users become familiar with a system

•2 common frameworks are:

•Mental Models

•Metaphors


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•Users develop an understanding of a system through learning & using it

•They develop knowledge of:•How to use the system (what to do next)•To a less extent, how the system works

•People make inferences using mental models of how to carry out tasks

•The more someone learns about a system and how it works, the more their mental model develops

Cognitive Frameworks - Mental Models


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•Craik (1943) described mental models as internal constructions of some aspect of the external world enabling predictions to be made

•Involves unconscious and conscious processes, where images and analogies are activated

•People sometimes uses erroneous mental models



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Example:

You arrive home on a cold winter’s night to a cold house. How do you get the house to warm up as quickly as possible?

Set the thermostat to be at its highest ?

Set the thermostat to the desired temperature?

• Typically, people select to set the heat to its highest setting to “get it to heat up as fast as possible”

• However, the thermostat will not heat any fasters at a higher setting - erroneous mental model



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Other Incorrect Mental Models:•Pressing the button at pedestrian lights – more presses, lights will change faster..

•Cursor freezes on the computer – press various different types of keys…

•Hit the TV to make it work..

•Voicemail: users assume messages are left on the phone immediately (as opposed to a central system with potential delay in transmitting messages)



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Three Aspects of Mental Models (Norman, 1990):•Design Model is the conceptualization that the designer has in mind

•User Model is what the user develops to explain the operation of the system

•System Image – ideally the user and design model are equivalent. However, they communicate only through the system itself



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Three Aspects of Mental Models (Norman, 1990):



DesignModel

UserModel

DesignerDesigner UserUser

SystemImage

SystemSystem

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•Another approach to conceptualizing how the mind works has been to use analogies and metaphors

•Metaphor is a figure of speech in which an expression is used to refer to something that it does not literally denote in order to suggest a similarity


Cognitive Frameworks - Metaphors

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•Most prevalent metaphor – “the mind is an information processor”

•Information enters and exits the mind through a series of processing steps

•The Human Information Processing (HIP) Model, which provides a basis from which to make predictions about human performance, models the cognitive processes of a user interacting with a computer


Cognitive Frameworks - Metaphors

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Encoding ComparisonResponseselection

Responseexecution

Attention

Memory

InputStimuli

OutputResponse

Conceptual Model


Cognitive Frameworks – Metaphors

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What goes on in the mind?

perceiving..thinking..remembering..learning..

understanding otherstalking with othersmanipulating others

planning a mealimagining a trippaintingwritingcomposing

making decisionssolving problemsdaydreaming...


Cognitive Processes

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•Human beings (e.g. users) are very complex•Variety of cognitive attributes have an important influence on screen design

H u m an P rocesses

P ercep tion A tten tion M em ory L earn in g


Cognitive Processes

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H u m an P rocesses

P ercep tion M em ory A tten tion L earn in g


Cognitive Processes - Perception

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•Perception is fundamental to interacting with computers

•To use a computer, a user needs to perceive information that is presented by the interface

•Perception can involve all the different senses (visual, hearing, touch, smell..)

•To date, mostly concerned with visual perception because screen is usually the interface

•Human visual perception has many limitations



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Perception

Classes of VisualPerception Theory

Techniques toGuide Perception

Constructive Ecological

Gestalt Laws Of Perception

Affordance



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•Two classes of Visual Perception Theory

•Constructive

•Ecological



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•Theory states that we construct our perception of the world from some of the sensory data falling on our senses

•Perception involves the intervention of representations and memory

•What we see is NOT a replica or copy of the world such as the image that a camera would produce

•The visual system constructs a model of the world by transforming, distorting, enhancing and disregarding information

•Anything perceived on a screen is also a result of our prior knowledge and expectations


Cognitive Processes – PerceptionConstructive

25Human Considerations

Cognitive Processes – PerceptionConstructive Example

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•Once we know what to look for, we recognise the picture

•Prior knowledge of what a dalmation looks like helps us to construct the image

•Without prior knowledge, we would not able to make sense of the picture

•Once we know what the picture depicts it is impossible to perceive it as random dots again, we have a meaningful interpretation



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•The Ruben vase/profile illusion is an ambiguous figure/ground illusion

•In this example, one line can have two shapes, depending on which side of the line is regarded as part of the figure



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•This is important as the visual system encodes objects primarily in terms of their contours

•Also elements close to one another or alike tend to be grouped together (grouping)

•The sudden reversal that you perceive may be due to your shift of attention on the shape of the contours

•This illusion involves higher cortical processing

•Stored information that contains knowledge about vases and profiles



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•Another aspect of the constructive process involves using context to interpret and understand what we perceive

•Not initially concerned with specific detail, more interested in the overall meaning of the scene

•This principle also applies to ambiguous information on computer screens



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Cognitive Processes – PerceptionConstructive - Gestalt

Gestalt laws of perceptual organisation‘Laws’ of perception that are regarded as being innate

•Proximity•Similarity•Closure•Continuity•Symmetry


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Proximity•the dots appear as groups rather than a random cluster of elements


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Similarity•there is a tendency for elements of the same shape or colour to be seen as belonging together


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Closure•missing parts of the figure are filled in to complete it, so that it appears as a whole circle


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Continuity•the stimulus appears to be made of two lines of dots traversing each other, rather than a random set of dots


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Symmetry•regions bounded by symmetrical borders tend to be perceived as coherent figures


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Cognitive Processes – PerceptionEcological

•Ecological theory argues that visual perception is a direct process

•Information is simply detected, not constructed

•Not really concerned with how we make sense of a scene

•Asks what we need to know about our environment in order to carry out our activities

•We will actively engage in activities to provide us with the necessary information


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Cognitive Processes – PerceptionEcological - Affordance

•A central concept of the ecological approach is the notion of affordance

•What we see as the behaviour of an object or system is that which is afforded or suggested by the object or system

•When the affordance of an object is perceptually obvious (perceptual affordance), it is easy for us to know how to interact with it

•When the opposite is true, we tend to make mistakes when trying to interact with the object


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• Scroll bars - intuitive to dragging upwards/downwards

• Lip-synch applications – lack of synchronisation disturbs our perception of what is happening

• Door handle – good affordance for pushing/pulling

Push

Pull


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•Affordance is very important with regards to interface objects such as buttons, scrollbars etc. (direct manipulation systems)

•Another type of affordance is sequential affordance

•This is where acting on one perceptual affordance leads to information indicating new affordances, e.g. when a scrollbar box is clicked, the feedback immediately shows the box in an animated state

•This affords moving the button up and down

•The first affordance lends itself to grabbing, the second to dragging


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Cognitive Processes – Perception

Must consider both in screen design

Perception

Constructive Ecological

Visual scene processedUse memory and experience to make sense of scene

Visual scene as isUse information in the scene (affordance)


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Cognitive Processes – Perception

Techniques used to guide perception

•Use of icons and graphical representations

•Use of audible, distinguishable sounds

•Speech output should enable users to distinguish between set of spoken words

•Legible and distinguishable text from its background

•Use of tactile feedback in virtual environments

•Use perceptual laws of grouping

•Use of perceptual boundaries (Windows)


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Summary of Lecture

Conclusion

•Human considerations in developing a user interfaces

•Cognitive FrameworksCognitive Frameworks•Mental Models•Metaphors

•Cognitive ProcessesCognitive Processes•Perception•Attention•Memory•Learning

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Terms of Reference

• Norman, D. (1990) The Design of Everyday Things

• Preece, J. et al. (2002) Interaction Design

• Shneiderman, B. & Plaisant, C. (2005) Designing the User Interface

• Benyon, D. et al (2005) Designing Interactive Systems

• Craik, K. (1943) The Nature of Explanation

References

1 the user lecture 2 date: 2 nd february ‘05. 2 overview of lecture introduce human considerations...

Documents

system slide

incorrect mental models

user cognition

user lecture

user interfaces

mind user model

numerous cognitive frameworks

system system image