Human Aspects: The user is considered as an information processing system herself/himself The term Cognition includes understanding, remembering, reasoning, attending, being aware, acquiring skills and creating ideas. Cognition plays an important role in Human Computer Interaction (HCI).

Cognitive Processes in HCI: Users give input to the computer by motor control (e.g. finger movements for pressing keys and moving the mouse), and output is typically provided through the screen, where the effects of providing input to the system are observed. recently: multimedia, handheld devices, voice and virtual reality rather than classical keyboard-mouse-screen environment.

Human Vision: Highly complex system. Primary source of information for most people. Raw image might not be the perceived image, because vision is often influenced by expectations about a visual scene and therefore interpretations of the visual scene.

Human Vision: Pictures by Fultz

Human Vision: Pictures by Fultz

Human Vision:

Perception and Representation: Constructivist and Ecological Approaches: Both argue that humans are active perceivers, but there are important differences in terms of the way these approaches explain perception.

Constructivist Approaches: Suggestion that people perceive actively by elaborating retinal images. Perception involves intervention of subjective representations and memories. Prior knowledge and experiences play a role in perceiving scenes (G. Sommerhoff: “We see what we expect to see”)

Organising Principles Perception of patterns as meaningful wholes defined by: Proximity Similarity Closure Continuity Symmetry

Ecological Approaches: People actively explore environment (seeing, smelling, hearing, tasting and touching). But different from Constructivist Approaches in that Ecological Approaches do not assume processes of elaboration that are based on prior knowledge (though they do not deny that prior knowledge is necessary).

Ecological Approaches try to explain how people deal with continuous events over time. These approaches ask what we need to know about our environment to carry out particular activities (e.g. finding a particular website with Google). Users will actively try to find the necessary information by applying the knowledge they have to find the answer.

Ecological approaches have been highly influential for theoretical accounts in user interface design. In User Interface Design, Visual perception is currently seen as the most important way to interact with the environment, followed by voice and hearing (e.g. in Speech Recognition of human voices and in the design of computerised voices) and haptic perception (e.g. touch in Virtual Reality Applications).

Speed and accuracy of movement play an important role, e.g. where on the screen to display particular icons so that they can be seen and reached easily. The most-used icons should be the best visible and the easiest ones to reach (e.g. by mouse, with touchscreen etc.). The other two senses, i.e. the smelling and tasting senses are not important in user interface design (at least so far).

Data Graphics Graphics can be instruments for reasoning about quantitative information (Tufte, 1983). Well designed data graphics are typically the ones that are simplest to understand and express complex information in a clear way.

Scatter Plot

Line Graph

Area Chart

Column/Bar Charts or Histograms

Stacked or Segmented Columns/Bars

Pie Charts

Start, Circular, Pattern or Radar Charts

Problems with Charts The variety of graphic techniques offered does not guarantee that they will be effectively applied. A chart for a high resolution colour screen may be reproduced in black and white when printed and therefore difficult to understand. For example, pie charts cannot order numbers along a visual dimension.

Attention and Memory Constraints: 3 different types of memory functions: 1. Sensory buffers 2. Short-term Memory = Working Memory 3. Long-term Memory.

Sensory Buffers Exist for each sensory channel that is important in relation to User Interface Design: iconic memory for visual stimuli echoic memory for aural stimuli haptic memory for touch

Sensory Buffers (continued) Sensoric Buffers are constantly overwritten by new information coming from these channels. Sensoric Buffers are extremely short-term: 0.5 seconds for visual stimuli. Not possible to give seconds for sounds, because they are received at different times.

Sensory Buffers (continued) Very brief play back of acoustic sounds is available to the Echoic Memory.

Short-term/Working Memory Acts as a scratch pad for the temporary recall of information. Is the working area where information is temporarily stored to be further processed for the following purposes: handling incoming information, selecting, retrieving, planning, storing, preparing outputs and actions.

Short-term/Working Memory continued Capacity is limited in amount and time. On average, the number of chunks we can remember is 7 (Magical Number 7  2, first reported by Miller, 1956). Chunk = digits, names, letters, other concepts

Relation between Sensory Buffer and Short-term Memory Information is passed from sensory buffer to Short-term memory. This happens through Attention. Attention = Mind concentrating on one or few of several competing stimuli or thoughts.

Relation between Sensory Buffer and Short-term Memory continued Attention thus acts as a filter for stimuli that compete at a particular time. People are able to focus their attention selectively, e.g. Cocktail Party phenomenon.

How can we apply this knowledge to User Interface Design If the probability that people get distracted is high, how can we get their attention back? How do we get people‘s attention to focus on the aspects they need to be looking at or listening to in order to do the task successfully?

How can we apply this knowledge to User Interface Design How can we guide people‘s attention to the relevant information on the display?

Long-term Memory Storage of facts, life experiences and procedures that are typically successful when performing a particular task. It also includes general knowledge. Information gets into the Long-term memory through Short-term=Working Memory after it has resided there for a couple of seconds.

Long-term Memory continued 2 types: Episodic and Semantic Memory Episodic Memory represents our memory of events that occurred in our lives, i.e. experiences we have made. Episodic Memory stores these experiences in a serial form.

Long-term Memory continued Episodic Memory lets us construct the events that took place at certain points of our lives. Examples of Episodic Memory are: One’s personal memory of learning how to ride a bike for the first time. One’s first kiss. One’s graduation, etc.

Long-term Memory continued Semantic Memory stores facts, concepts and skills that we have acquired. For example: One’s knowledge of how to use UNIX. One’s skill knowledge of how to ride a bike. One’s knowledge of London’s population size.

Long-term Memory continued Episodic and Semantic Memory are related towards some extent. Information in Semantic Memory is derived from Episodic Memory, because our personal experiences can support us in learning new facts and concepts.

Long-term Memory continued The Structure in Semantic Memory allows to access information, to represent relationships between pieces of information and may suffer from interference between different pieces of information.

Long-term Memory continued 3 Main properties of Long-term Memory: 1. Storage/Memory of Information 2. Forgetting 3. Information Retrieval

Relation between Short- term and Long-term Memory Information from Short-term/Working Memory is transmitted to Long-term Memory through rehearsal. However, information must be meaningful, because repetition alone is not enough for information to be successfully transmitted into Long-term memory.

Relation between Short- term and Long-term Memory continued Meaningful information can be related to already existing structures in Long-term Memory, which makes it easier to remember. This is important in relation to User Interface Design. It is good to design applications that can be related to already existing structures.

Forgetting Two main theories (Dix et al. 1993): 1. Decay (information decays with time) 2. Interference (information is not accessible due to interference between competing information. New information causes loss of old information, but the cause of loss is not time itself)

Meaningful Interfaces Learning and Memory play an important role in the design of meaningful interfaces. The specific memory processes that play a role are: 1. Recall 2. Recognition

Recall and Recognition Recall: Information is reproduced from memory, e.g. if you learn a list of words and are later asked to reproduce the list of words. Recognition: Memorised information is not reproduced, but must be chosen out of a list of possible alternatives, e.g. if you learn a list of words and are later asked to tick the words you have experienced during the learning phase on a list that also includes other words.

Recall and Recognition continued The decay of learnt information is much larger under Recall conditions. Under Recognition conditions, there is much less decay: long-term recognition after a couple of minutes is often similar to that after hours or days.

How can the findings about Recall and Recognition be applied to User Interface Design? It is well-known that people recognise material far easier than they recall material. Reduction of interfaces that rely on the recall of information, e.g. sequences of commands.

How can the findings about Recall and Recognition be applied to User Interface Design? continued Instead: Interfaces where users have the ability to recognise the necessary information, e.g. graphical user interfaces in Windows instead of written commands in MS-DOS. This way users do not have to remember sequences of commands.

Other Aspects of Meaningful Interfaces In general, meaningfulness of a stimulus or concept is determined by their familiarity and associated imagery. Meaningfulness determines the extent to which new material can be remembered.

Other Aspects of Meaningful Interfaces continued Specifically related to User Interface Design, the perceived meaningfulness of icons appearing on visual display depends on: 1. Context in which icon is used 2. The task for which icon is used 3. The design (surface form) of icon 4. The type of underlying concept that is represented.

Other Aspects of Meaningful Interfaces continued Specifically related to User Interface Design, the command names are also important to consider. It is useful to consider the characteristics of the potential users, the context in which the interface is likely to be applied and the cultural characteristics of the group that is using the commands to prevent misunderstandings.

Other Aspects of Meaningful Interfaces continued Specifically related to User Interface Design, there are additional techniques to highlight attention. Making use of spatial and temporal cues, e.g. incorporate animations. Making use of colour or different shades. Flashing, reverse video and acoustic information.

Provide systematic information about the status of activity (what is currently done and what still needs to be done - you often see this when installing a program and you need to press next repeatedly. Ideally, the system should let people return to the point where they interrupt a particular task if they need to interrupt the process and want to return later without repeating the whole process.

Routine tasks that are likely to be forgotten should be brought to the user’s attention, e.g. by prompting the user whether s/he wants to save the file.

Focusing attention at the interface Urgent and important information (e.g. warning messages) should be placed at the best visible place. Less urgent information should be placed at specific areas of the screen (this particular area should be used consistently so that the user always knows where s/he can find this type of information).

Focusing attention at the interface continued Rarely needed information should not be placed in the screen area (e.g. help options), but they should be easy to reach (e.g. through the menu). A good interaction design places a high weight on consistency, e.g. changes should be as limited as possible from one screen display to the next.

Focusing attention at the interface continued Consistency also applies to buttons, words to describe specific terms and icons, which should always appear on the same location and which should always have the same shape and size. Try to assess how much information is needed to make the application as simple as possible, and avoid to include any unnecessary information.

Focusing attention at the interface continued By trying to simplify, the following guidelines may help: 1. Use concise wording of instructions, messages and other text. 2. Use icons that are simple to recognise and that tell as much as possible about the application.

Focusing attention at the interface continued By trying to simplify, the following guidelines may help: 3. Minimise the overall density on the screen. 4. Minimise the local density in particular areas of the screen, e.g. avoid having too much information at the top or bottom, left or right.

Focusing attention at the interface continued By trying to simplify, the following guidelines may help: 5. Use plenty of white (empty) space around text so that it is better visible. 6. Try to maintain a logical structure on the screen by placing things that belong to each other near each other.

Focusing attention at the interface continued All these guidelines are important for user interfaces with the classical keyboard, mouse and screen environment. However, they become even more important for handheld devices, where size of the visual display is very limited.