hci-lecture02

7/24/2019 HCI-Lecture02

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Human ComputerInteraction

Lecture 2

The Human


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The Human

Think of human as an informationprocessing system, which containsinput/output, stores information andprocesses information

We will therefore consider threecomponents of this system: input

output, memory and processing


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The Human

Information i/o !

"isual, auditory, haptic, mo"ement

Information stored in memory

sensory, shortterm, longterm

Information processed and applied

reasoning, pro#lem sol"ing, skill, error

$motion in%uences human capa#ilities

$ach person is di&erent


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'ision

Two stages in "ision

( physical reception of stimulus

( processing and interpretation ofstimulus


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The $ye physical reception

mechanism for recei"ing light andtransforming it into electrical energy

light is re%ected from o#)ects

images are focused upsidedown onretina

retina contains rods for low light

"ision* +ods are responsi#le for "isionin darkness* ppro-imately .2million rods*


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The $ye physical reception

+etina also contains cones for colour"ision* They are responsi#le for "isionin light*

Cones are concentrated on fo"ea androds are concentrated on retina

0lind spot contains neither rods nor

cones* 1anglion cells #rain34 detect pattern

and mo"ement


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5esign 6ocus

user concentrating on the middleof the screen cannot #e e-pected toread help te-t on the #ottom line*

7o if an error message is to #e shownto user, what to do888


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5esign 6ocus

user concentrating on the middleof the screen cannot #e e-pected toread help te-t on the #ottom line*

7o if an error message is to #e shownto user, what to do888

0etter use %ashing error message

What a#out cle"er mo"ing icons*


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Interpreting the signal cont4

0rightness su#)ecti"e reaction to le"els of light

a&ected #y luminance of o#)ect, which is

the amount of light emitted #y an o#)ect Contrast is luminance of o#)ect and

luminance of its #ackground

"isual acuity increases with luminanceas does %icker*

High display luminance systems areseen to %icker e"en a#o"e 9 H*


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Interpreting the signalcont4

Colour made up of hue, intensity, saturation

Hue is determined #y the spectral wa"elength of the light ppro-imately .9 di&erent hues can #e discriminated #y the a"erage

person

Intensity is the #rightness of color

7aturation is the amount of whiteness in color

Cones are sensiti"e to colour wa"elengths*Three types of cones red, green and #lue4

#lue acuity is lowest, #ecause only ;= males and .= females colour #lind


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Interpreting the signal cont4

?ur e-pectations a&ect the way animage is percei"ed*

Conte-t is used to resol"e am#iguity

Howe"er, ?ptical illusions sometimesoccur due to a#o"e factors


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?ptical Illusions

the @ono illusionthe Auller Lyer illusion


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+eading

7e"eral stages: "isual pattern percei"ed

decoded using internal representation of language

interpreted using knowledge of synta- and

semantics

+eading in"ol"es saccades)erky mo"ements4and B-ations

@erception occurs during B-ations

Word shape is important to recognition

egati"e contrast dark character on a lightscreen4 impro"es reading from computerscreen


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5esign 6ocus

7tandard font sies of D to .2 areeEually legi#le, gi"en proportional

spacing #etween lines* 7imilarly line lengths of #etween 2*;

and 9*2 inches 9> and .;2 mm4 areeEually legi#le*

e"ertheless, reading from a computerscreen is slower than from a #ook*Howe"er, this fact can #e controlled #y

careful design of te-tual interfaces*


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Hearing

7ound can con"ey a remarka#le amount of information

@ro"ides information a#out en"ironment:distances, directions, o#)ects etc*

@hysical apparatus:

outer ear F protects inner and ampliBes sound middle ear F transmits sound wa"es as

"i#rations to innerear

inner ear F chemical transmitters are releasedand cause impulses in auditory ner"e

7ound

pitch F sound freEuency loudness F amplitude

tim#re F type or Euality


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Hearing cont4

Humans can hear freEuencies from 2H to.9kH less accurate distinguishing high freEuencies than low*

uditory system Blters sounds can attend to sounds o"er #ackground noise*

for e-ample, the cocktail party phenomenon*

7ound could #e used e-tensi"ely in interfacedesign to con"ey information a#out the systemstate


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Touch

@ro"ides important feed#ack a#out en"ironment*

Aay #e key sense for someone who is "isuallyimpaired*

7timulus recei"ed "ia receptors in the skin: thermoreceptors F heat and cold

nociceptors F pain

mechanoreceptors F pressure

7ome areas more sensiti"e than others e*g*6ingers and hair


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Ao"ement

6ittsG Law descri#es the time taken to hit a screentarget:

At a # log25/7 .4

where: a and # are empiricallygained #y means ofo#ser"ations4 determined constants

At is mo"ement time

5 is 5istance

7 is 7ie of target

targets as large as possi#le distances as small aspossi#le


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Aemory

There are three types of memory function:

7ensory memories

7hortterm memory or working memory

Longterm memory


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7ensory Aemory

0u&ers for stimuli recei"ed through senses

iconic memory: "isual stimuli

echoic memory: aural stimuli

haptic memory: touch stimuli

$-amples: Ao"e your Bnger fastly #efore

you, JsparklerK trail Continuouslyo"erwritten

Information is passed to 7TA #y attention


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7hortterm memory 7TA4

What is the result of ;9 M888

7cratchpad for temporary recall rapid access

rapid decay

limited capacity NO 2 @rinciple


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$-amples

2.2;2N>

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