The User Lecture 2 DeSiaMore www.desiamore.com/ifm

Overview of Lecture Introduce human considerations in developing a user interfaces DeSiaMore www.desiamore.com/ifm

The user is the most important entity of the system DeSiaMore www.desiamore.com/ifm

The User The User Nature of User Human Considerations DeSiaMore www.desiamore.com/ifm

Nature of User User Groups Reminder - Computer skills & knowledge Disabilities Age Cultural DeSiaMore Nature of User www.desiamore.com/ifm

The User The User Nature of User Human Considerations DeSiaMore www.desiamore.com/ifm

Human Considerations 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 DeSiaMore Human Considerations www.desiamore.com/ifm

Cognitive Frameworks Cognitive frameworks help us to understand how users become familiar with a system 2 common frameworks are: Mental Models Metaphors DeSiaMore Human Considerations www.desiamore.com/ifm

Cognitive Frameworks - Mental Models 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 DeSiaMore Human Considerations www.desiamore.com/ifm

Cognitive Frameworks - Mental Models 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 Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Frameworks - Mental Models Three Aspects of Mental Models (Norman, 1990): Design Model is the conceptualisation 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 Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Frameworks - Mental Models Three Aspects of Mental Models (Norman, 1990): Design Model User Model Designer User System System Image Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Frameworks - Metaphors 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 Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Frameworks - Metaphors 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 Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Processes Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Processes Human beings (e.g. users) are very complex Variety of cognitive attributes have an important influence on screen design Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Processes - Perception Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Processes - Perception 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 Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Processes - Perception Classes of Visual Perception Theory Techniques to Guide Perception Constructive Ecological Gestalt Laws Of Perception Affordance Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Processes - Perception Two classes of Visual Perception Theory Constructive Ecological Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Processes – Perception Constructive 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 Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Processes – Perception Constructive Example Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Processes – Perception Constructive Example 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 Human Considerations DeSiaMore www.desiamore.com/ifm

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Cognitive Processes – Perception Constructive Example 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 Human Considerations DeSiaMore www.desiamore.com/ifm

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Cognitive Processes – Perception Constructive Example 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 Stored information that contains knowledge about vases and profiles Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Processes – Perception Constructive Example 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 Human Considerations DeSiaMore www.desiamore.com/ifm

Cognitive Processes – Perception Ecological 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 DeSiaMore Human Considerations www.desiamore.com/ifm

Cognitive Processes – Perception Ecological - 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 DeSiaMore Human Considerations www.desiamore.com/ifm

Cognitive Processes – Perception Ecological - Affordance 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 Pull Push DeSiaMore Human Considerations www.desiamore.com/ifm

Cognitive Processes – Perception Ecological - Affordance Affordance is very important with regards to interface objects such as buttons, scrollbars etc. (direct manipulation systems) DeSiaMore Human Considerations www.desiamore.com/ifm

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) DeSiaMore Human Considerations www.desiamore.com/ifm

Summary of Lecture Human considerations in developing a user interfaces Cognitive Frameworks Mental Models Metaphors Cognitive Processes Perception Attention Memory Learning Conclusion DeSiaMore www.desiamore.com/ifm

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 DeSiaMore References www.desiamore.com/ifm