L ECTURE 2: UNDERSTANDING T HE H UMAN Topics of interst: Cognitive aspects Mental Models Problem solving

T HE H UMAN In order to design something for some one, we need to understand the capabilities and limitations of that person. This chapter covers how humans perceive the world around them, how they store, process info, solve problems & how they physically manipulate objects Information i/o via visual Auditory: - Speech Haptic -touch movement channels e.g. figures Information is stored in memory (short and long term memory) Information is processed and applied in problem solving

T HE H UMAN Modality : It is a general class of 1. A sense – through which the human can receive the output of the computer 2. A Sensor or device through which the computer can receive the input from the human. In short: Modality is a path of communication between the human and the computer. It can be visual based, Audio-based and Sensor- based (Combination) Major modalities: Seeing or vision modality, Hearing or audition modality. Haptic Modalities: Touch, tactile modality - the sense of pressure Other Modalities: Taste or gustation modality, Smell or olfaction modality, thermoception modality – the sense of heat or the cold

I NDIVIDUAL DIFFERENCES long term - sex, physical and intellectual abilities short term - effect of stress or fatigue changing – age Qn: will design decision exclude section of user population? Multitasking (when attention can be divided) What humans can do Multitasking (when attention can be divided) Routinized tasks Difficult tasks (problem solving)

M ULTITASKING : WHEN YOU CAN AND WHEN YOU CANNOT You are a medium level skier. You are coming down a steep slope for the first time. Try to spell your name backward while you do that. On the other hand, as you drive your car, you can listen to the music, watch out for road signs, and sometimes make phone calls. In HCI design not all situations can handle Multitasking effectively

C OGNITIVE PROCESSES Attention Perception and recognition Memory Learning Reading, speaking and listening Problem-solving, planning, reasoning and decision- making

7 A TTENTION Selecting things to concentrate on at a point in time from the mass of stimuli around us Allows us to to focus on information that is relevant to what we are doing Involves audio and/or visual senses Focussed and divided attention enables us to be selective in terms of the mass of competing stimuli but limits our ability to keep track of all events Information at the interface should be structured to capture users’ attention, e.g. use perceptual boundaries (windows), colour, reverse video, sound and flashing lights

Techniques for getting attention Spatial and temporal cues (layouts and animations) Color Alerting techniques such as flashing and reverse video and auditory warnings Using interface standards that are familiar to users (same look & feel) “ Everyone knows what attention is. It is the taking possession of mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought... It requires withdrawal from some things in order to deal effectively with others.” William James

9 P ERCEPTION How information is acquired from the world and transformed into experiences Obvious implication is to design representations that are readily perceivable, e.g. Text should be legible Icons should be easy to distinguish and read

10 R ECOGNITION VERSUS RECALL Command-based interfaces require users to recall from memory a name from a possible set of 100s GUIs provide visually-based options that users need only browse through until they recognize one Web browsers, MP3 players, etc., provide lists of visited URLs, song titles etc., that support recognition memory

11 M EMORY Involves first encoding and then retrieving knowledge We don’t remember everything - involves filtering and processing what is attended to Context is important in affecting our memory (i.e. where, when) We recognize things much better than being able to recall things

12 L EARNING Acquiring; - New concepts, - New skills and - New knowledge In the HCI context, it refers to how users learn to use; new interfaces It is difficult for an adult to learn Solution: minimize learning How to learn to use a computer-based application Using a computer-based application to understand a given topic People find it hard to learn by following instructions in a manual prefer to learn by doing

13 R EADING, SPEAKING, AND LISTENING The ease with which people can read, listen, or speak differs Many prefer listening to reading Reading can be quicker than speaking or listening Listening requires less cognitive effort than reading or speaking Dyslexics have difficulties understanding and recognizing written words

Vision Two stages in vision physical reception of stimulus: Mechanism for receiving light and transforming it into electrical energy which in turn reflects (mirrors) object processing and interpretation of stimulus s ize and depth -visual angle indicates how much view object occupies ( relates to size and distance from eye) e.g. view of a tree thru window different from view when outside -visual acuity is ability to perceive detail. Size of visual angle affects acuity -Familiar objects perceived as constant size ( in spite of changes in visual angle when far away) Information i/o via

Interpreting the signal (cont) Brightness subjective reaction to levels of light affected by luminance (amount of light emitted by an object) of object measured by just noticeable difference. Contrast (difference) related to luminance of an object & that of its background visual acuity increases with luminance Color Perception comprises of hue (shade), intensity (brightness), saturation (amount of whiteness) (visual cortex retina has rods for B&W vision, cones (in fovea) for color.) Eye perceives color b’se cones are sensitive to light of different wavelengths (blue has shortest, green medium & red long) blue acuity is lowest 8% males and 1% females color blind-can’t distinguish btn green & red Vision

THE COMMANDMENTS OF COLOR 1.Use a maximum of five, plus or minus two colors. Four distinct colors are appropriate. Allows extra room in short- term memory which can store five words or shapes, six letters, seven colors, and eight digits. Use spectral order in color coding -- red, orange, yellow, green, blue, indigo, violet. 2.Use foveal (center) and peripheral colors appropriately. Use blue for large areas, not for text type. Blue is good for slide and screen backgrounds. Use red and green to capture attention. The visual field adapts easily to this. 3.Use same color for grouping related elements. 4.Use high value, high saturation colors to draw attention. Use brighter colors for older folks.

Reading Concerned with processing text Stages: visual pattern perceived e.g. of the word Study decoded using internal representation of language (English) i.e. knowledge of syntax, semantics, pragmatics (sensible) During reading, eye moves back and forth-regressions. If text is complex, there’ll be more regressions Speed of reading depends on legibility (9-12 points), line spacing & line length( inches) Reading from comp slower than bk hence fewer words on a page, dark characters on a light screen (negative contrast) increases acuity

Hearing Provides information about environment: distances, directions, objects etc. E.g. “There is a man behind the house” identify the distance, direction and object components in this statement? Physical apparatus: outer ear- protects inner and amplifies sound middle ear- transmits sound waves as vibrations to inner ear inner ear- chemical transmitters are released and cause impulses in auditory nerve. Sound pitch- sound frequency loudness - amplitude timbre- type or quality

Hearing (cont) Humans can hear frequencies from 20Hz to 15kHz less accurate distinguishing high frequencies than low. Auditory system filters sounds can attend to sounds over background noise. e.g. cocktail party phenomenon.

Touch Provides important feedback about environment. May be key sense for someone who is visually impaired e.g feeling button depress is vital. Stimulus received via receptors in the skin: thermoreceptors - heat and cold nociceptors - pain mechanoreceptors – pressure-what we’re concerned with in HCI Some areas more sensitive than others e.g. fingers

Movement e.g hitting a button Time taken to respond to stimulus: reaction time + movement time Movement time - dependent on age, fitness etc. Reaction time - dependent on stimulus type: visual ~ 200ms (millisecond) auditory ~ 150 ms pain ~ 700ms

Memory There are three types of memory function: Sensory memories or sensory storage ( buffer for stimuli: Holds info from the eyes ( iconic storage ) and ears ( echoic storage ). This information is stored for a brief time. MUST ENTER WORKING MEMORY OR BE LOST. Short-term memory or working memory Long-term memory Selection of stimuli governed by level of arousal.

Short-term memory (STM) Scratch-pad for temporary recall e.g. names of some people at a party rapid access ~ 70ms rapid decay ~ 200ms limited capacity - 7± 2 chunks The capacity of short-term memory is small -- info will disappear within 20 seconds unless it is repeated or practiced. Chunking: grouping and organizing information to fit into meaningful units. The size of chunks does affect ability to remember.

Long-term memory (LTM) Repository for all our knowledge slow access ~ 1/10 second slow decay, if any huge or unlimited capacity Once information is transferred to long term memory, it is there forever - the problem is accessibility or retrieval. - the basic debate is how info is located and retrieved, and how many long term memory subsystems exist. Two types episodic - serial memory of events like memories of key events in one’s life semantic - structured memory of facts, concepts, skills information in semantic LTM derived from episodic LTM.

Long-term memory (cont.) Semantic memory structure provides access to information Represents relationships between bits of information Supports inference Model: semantic network inheritance - child nodes inherit properties of parent nodes relationships between bits of information explicit (clear) supports inference through inheritance

Long-term memory - semantic network

DOG Fixed legs: 4 Default diet: carniverous sound: bark Variable size: colour COLLIE Fixed breed of: DOG type: sheepdog Default size: 65 cm Variable colour Models of LTM - Frames Information organized in data structures Slots in structure instantiated with values for instance of data Type-subtype relationships

Models of LTM - Scripts Model of stereotypical information required to interpret situation Script has elements that can be instantiated with values for context Script for a visit to the vet Entry conditions:dog ill vet open owner has money Result:dog better owner poorer vet richer Props:examination table medicine instruments Roles:vet examines diagnoses treats owner brings dog in pays takes dog out Scenes:arriving at reception waiting in room examination paying Tracks:dog needs medicine dog needs operation

Representation of procedural (routine) knowledge. Condition/action rules if condition is matched then use rule to determine action. Models of LTM - Production rules IF dog is wagging tail THEN pat dog IF dog is growling THEN run away Another good example is illness. Most people can tell when they’ve malaria

decay information is lost gradually but very slowly interference ( info gets mixed up with other info) new information replaces old: retroactive interference old may interfere with new: proactive interference affected by emotion - can subconsciously `choose' to forget e.g??? LTM - Forgetting

recall information reproduced from memory can be assisted by cues e.g. categories recognition information given based on what has been seen before less complex than recall due to cues e.g. metaphors used in computing. LTM - retrieval

Thinking: reasoning and problem solving Reasoning Deductive: derive logically necessary conclusion from given premises. e.g. If it is Friday then she will go to work It is Friday Therefore she will go to work. Logical conclusion not necessarily true what if she’s sick this friday?

Inductive Reasoning Inductive: generalize from cases seen to cases unseen e.g. all elephants we have seen have trunks therefore all elephants have trunks.

Abductive reasoning reasoning from event to cause e.g. Sam drives fast when drunk. If you see Sam driving fast, assume drunk. Unreliable: can lead to false explanations.

P ROBLEM SOLVING According to the American Heritage Dictionary: Problem solving is the process of devising and implementing a strategy for finding a solution or for transforming a less desirable condition into a more desirable one. When solving problems, we: - Set up goals - Plan our actions - Execute actions - Evaluate if actions help us achieve goals - Change strategies if necessary

Problem solving Process of finding solution to unfamiliar task using knowledge. Several theories. Gestalt problem solving both productive (insight) and reproductive (using existing knowledge) productive draws on insight and restructuring of problem attractive but not enough evidence to explain `insight’

Problem solving (cont.) Problem space theory problem space comprises problem states (initial state and goal state ) & p’ple use operators to move from former to latter heuristcs may be employed to select appropriate operators e.g. means-ends analysis-initial state compared with goal state & operators chosen to reach goal e.g. moving desk in your office largely applied to problem solving in well-defined areas e.g. puzzles rather than knowledge intensive areas

Problem Solving Cycle

M ENTAL MODELS Definition: are representations in the mind of real or imaginary situations The mind constructs "small-scale models" of reality that it uses to anticipate events Mental models can be either constructed from the way a system looks, how it behaves, or from a metaphor of a situation already known to us

40 M ENTAL MODELS Users develop an understanding of a system through learning about and using it Knowledge is sometimes described as a mental model: How to use the system (what to do next) What to do with unfamiliar systems or unexpected situations (how the system works) People make inferences using mental models of how to carry out tasks

41 M ENTAL 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 images and analogies are activated Deep versus shallow models e.g. how to drive a car and how it works

M ENTAL MODELS Mental models allow people to make predictions about how things work and how to use something - How does your car start? - How does an ATM machine work? - How does your computer boot? We use mental models to deal with new and unfamiliar environments based on our existing knowledge

Errors and mental models Types of error slips right intention, but failed to do it right causes: poor physical skill e.g. car parking, inattention etc. change to aspect of skilled behaviour can cause slip. They happen by accident, such as making “typos” by pressing the wrong key or selecting wrong menu item by overshooting. The most frequent errors are slips, especially in well-learned behavior. mistakes ( An incorrect action is taken based on an incorrect decision.) wrong intention cause: incorrect understanding - humans create mental models to explain behaviour. if wrong (different from actual system) errors can occur.

Cognitive Psychology and Interactive System Design Some direct applications e.g. blue acuity is poor  blue should not be used for important detail. However, correct application generally requires understanding of context in psychology A lot of knowledge has been distilled in guidelines - see Lecture 4 & 5 experimental and analytic evaluation techniques – see Lecture 9

R EFERENCES & A DDITIONAL R EADING Alan Dix, Janet Finlay, Gregory Abowd & Russell Beale (2004). Human-Computer Interaction. Hillsdale, NJ: Prentice Hall, ISBN (hardback); (paperback) only outside USA (Second Edition) ISBN Chap. 1 Assign (To be done in groups) “To design a good system for users it is needed to understand the capabilities and limitations of those different people.” Explain the term Universality. Explain the following barriers together with the corresponding personal assistive technologies. 1. Sensory 2. Physical, 3. Cognitive and 4. Age Associated Barrier Explain in detail the PS cycle and the 7 principles of problem solving (PS)