PowerPoint Presentation

HUMAN

RoadmapInformation I/O channelsResponding to stimulusHuman memoryThinkingErrors and mental modelsEmotion vs. human capabilitiesUsers individual differencesPsychology and the design of interactive systemsThe HumanUser Information Processing SystemInformationComes in(Input)Is stored(Memory)Is processed(Processing)Is passed out(Output)

Information I/O ChannelsInformation Input / Output:Human beings interaction dependent on information being received and given: input and output.

Interaction with computerUser receives information that is output by the computerResponds by providing input to the computeri.e. users output (user gives) becomes computers input and the users input (user receives) becomes the computers output.Human I/O Channels Input : Senses InvolvedVisual sense/vision (sight)Auditory sense/hearing (sound)Sense of touch (hap tic)Sense of smellSense of taste

Vision, hearing and touch are currently the ones being significantly used in HCI.

Output: Motor control of effectorsEffectors are body parts that can respond to stimulation e.g. fingers, eyes, head, foot, vocal system, etc

ExampleComputer with keyboard and mouseApplication: GUI, Menus & IconsInformation ReceivedSightEarsTouchInformation SentHands: Keyboard, mouse

Vision

Vision is primary source of information for humans

Visual Perception --Two stages

Physical reception of Stimulus

Processing and Interpretation of StimulusEye and InterfacesInterpretation and/or Perception of size and depth, brightness and color, each of which is crucial to the design of effective visual interfacesEye

The Eye - Physical ReceptionMechanism for receiving light and transforming it into electrical energy

Light reflects from objectsImages are focused upside-down on retina

Retina contains Photoreceptors:Rods: Highly sensitive to light for low light visionCones: For colour vision

Ganglion cells detectPatternmovement

Interpreting the SignalSize and depthVisual Angle indicates how much of view object occupiesrelates to size and distance from eyeVisual Acuity is ability to perceive detailFamiliar objects perceived as constant size In spite of changes in visual angle when far awayCues like overlapping help perception of size and depth

Interpreting the Signal (cont)BrightnessSubjective reaction to levels of lightAffected by luminance of objectVisual acuity increases with luminance as does flicker

ColourMade up of hue, intensity, saturationCones sensitive to colour wavelengthsRed, Green, Blue8% males and 1% females colour blind

Interpreting the Signal - ColourHueHue is what most people think of when we say colorHue is the name of a distinct color of the spectrum, It is the particular wavelength frequency

SaturationSaturation is the purity of a colour

Value (Intensity, Brightness, Lightness)Refers to the intensity of light present. When light is at its fullest intensity, colors will become bright Unlike saturation, there isn't necessarily less of the color it is just not as intense

Interpreting the Signal (cont)The visual system compensates for:movementchanges in luminance

Context is used to resolve ambiguity

Optical illusions sometimes occur due to over compensationInterpreting the SignalAmbiguity

B or 13 ???

Context is used to resolve ambiguityInterpret & exploit the expectation

Optical IllusionsThe Ponzo illusionThe Muller Lyer illusion

The Proof Reading IllusionHearingProvides information about environment:distances, directions, objects etc.

Physical apparatus:outer earprotects inner and amplifies soundmiddle eartransmits sound waves as vibrations to inner earinner earchemical transmitters are released and cause impulses in auditory nerve

HearingSoundPitchsound frequencyLoudness amplitudeTimbretype or quality

Hearing (cont)Humans can hear frequencies from 20Hz to 15kHzLess accurate distinguishing high frequencies than low.

Auditory system filters soundsCan attend to sounds over background noiseFor example the cocktail party phenomenon.

TouchProvides important feedback about environment.May be key sense for someone who is visually impaired.Stimulus received via receptors in the skin:thermoreceptors heat and coldnociceptors painmechanoreceptors pressure (some instant, some continuous)Some areas more sensitive than others e.g. fingers.Kinethesis - awareness of body position Question: Ecommerce (CDs & Books vs. Clothes)

MovementFitts Law:Describes the time taken to hit a screen target

Movement Time = a + b log2(D/S + 1)where: a and b are empirically determined constantsD is Distance from target centreS is Size of targetImportant: D & S are calculated along the axis of motion

MovementMovement Time = a + b log2(D/S + 1)

Fitts Law

Index of Difficulty=> Targets as large as possible=> Distances as small as possibleMovementPie-chart shaped menusAll options are equidistant (As opposed to lists)Increased used of screen estate

Responding to StimulusTime taken to respond to stimulus =Reaction time + Movement time

Movement time: dependent on age, fitness, etc.

Reaction time: dependent on stimulus type e.g.visual~ 200msauditory~ 150 mspain~ 700ms

Increasing reaction time decreases accuracy in the unskilled operator but not in the skilled operator.HUMAN MEMORYThere are three types of memory function:

1. Sensory memory

2. Short-term memory or working memory

3. Long-term memory

Selection of stimuli is governed by Level of Interest.

Human Memory

Sensory memoryBuffers for stimuli received through sensesIconic memory: visual stimuliEchoic memory: aural stimuliHaptic memory: tactile stimuli

Continuously overwritten

Transmitted from Sensory Memory to Working MemoryExamplesDuring firework displays, moving sparklers leave a persistent image

Concentration of mind on one out of a number of competing stimuli or thoughts As in cocktail party

Have you ever had someone ask you a question when you are reading? You ask them to repeat the question, only to realize that you know what was asked after all.

Short Term Memory (STM)Temporary recall of informationReading a sentence, Performing an arithmetic operation etc.Rapid access: order of 70msRapid decay: order of 200msLimited capacity: 7 2 chunks

Chunking Information can increase short term memoryPattern AbstractionShort-term memory (STM)Examples

212348278493202

44 113 245 8920 (chunks with pattern, easier to remember)

HEC ATR ANU PTH ETR EET (chunks without pattern, not easy to remember)Long-term memory (LTM)Repository for all our knowledgeSlow access ~ 1/10 secondSlow decay, if anyHuge or unlimited capacity

Long Term Memory

Events and ExperiencesFacts

How to ..Long Term Memory1. Episodic memory:It represents our memory of events and experiences in a serial form.It is from this memory that we can reconstruct the actual events that took place at a given point in our lives.

2. Semantic memory:It is a structured record of facts, concepts, skills that we have acquired. It is structured in some way to allow access to information, representation of relationships between pieces of information, and inference.

Long-term Memory (cont.)Memory models used to explain how we represent and store knowledge1. Semantic networks2. Frames3. Scripts4. Production system

1. Semantic NetworksRepresent the associations and relationships between items in memory.2. FramesExtend semantic nets to include structured, hierarchical information. They represent knowledge items in a way which makes explicit the relative importance of each piece of information. Information organized in data structures.Slots in structure instantiated with values for instance of data.Type-subtype relationships. 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

3. ScriptsAttempt to model the representation of stereotypical knowledge about situations.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 vetEntry conditions:dog illvet openowner has money

Result:dog betterowner poorervet richer

Props:examination tablemedicineinstrumentsRoles:vet examines diagnoses treatsowner brings dog in pays takes dog out

Scenes:arriving at receptionwaiting in roomexaminationpaying

Tracks:dog needs medicinedog needs operationRepresentation of procedural knowledge. Condition/action rules if condition is matchedthen use rule to determine action.IF dog is wagging tailTHEN pat dog

IF dog is growlingTHEN run away4. Production SystemLong Term Memory -- ProcessesStorage

Forgetting

Retrieval

LTM - Storage of information1. RehearsalInformation moves from STM to LTMTotal Time hypothesisAmount of information retained is proportional to rehearsal (or learning) timeDistribution of practice effectOptimized by spreading learning over time

2. Structure, Meaning and FamiliarityIf information is Structured, Meaningful or Familiar, it becomes easier to remember

Past, Faith, Idea, Cold, Value, Courtesy, Logic, Quiet, AmbitiousBoat, Tree, Cat, Child, Gun, Plate, Home, Table, Computer, SpoonLTM - Forgetting1. DecayInformation is lost gradually but very slowly2. InterferenceNew information replaces old: Retroactive interferencee.g. if you change telephone numbers, learning your new number makes it more difficult to remember your old number.However sometimes the old may interfere with new: proactive inhibition e.g. when you find yourself driving to your old house rather than your new one.3. EmotionWe tend to remember highly emotive events rather than mundane ones.Do we ever actually forget anything or does it just become increasingly difficult to access certain items from memory? (debatable)

LTM - RetrievalRecall Information reproduced from memory can be assisted by cues, e.g. Categories, imageryAct of reproducing a specific incident, fact or other item (from LTM)Recalling where you were last weekend, fill-in-the-blank on exams RecognitionInformation gives knowledge that it has been seen beforeLess complex than recallPeople are more likely to recognize a suspect in a police line-up than to provide an accurate description from recall memoryIt is easier to answer multiple-choice questions than essay questions because the correct answer may be recognized