-
EvaluatingAnimationin thePeripheryasa Mechanismfor
MaintainingAwareness
D. Scott McCrickard Richard Catrambone John T.
StaskoDepartmentof ComputerScience Schoolof Psychology Collegeof
Computing
VirginiaPolytechnicInstitute andGVU Center andGVU
CenterandStateUniversity Georgia Instituteof Technology Georgia
Instituteof Technology
Blacksburg VA 24061-0106USA AtlantaGA 30332-0170USA AtlantaGA
[email protected] [email protected]
[email protected]
Abstract: Small
animateddisplayssuchastickersandfadersareincreasinglybeingusedto
convey informationon computerscreens.Relatively little is
understood,however, abouttheir useasperipheraldisplays,that is,
toolsfor communicatinglower-priority awarenessinformation to
people. This article describestwo experimentsthatexaminethe
tradeoff of communicationcapability versusdistractionin
peripheraldisplays. We found that thepresenceof animatedtextual
peripheraldisplaysdid not distractpeoplefrom a
centralinformationbrowsingtask,andwe
identifiedparticularanimationanddisplaycharacteristicsthatfacilitatedifferentinformation-centrictasks.
Keywords:
peripheraldisplays,awareness,monitoring,animation,empiricalevaluation,dual-taskevaluation
1 Intr oductionPeoplenaturallywish to staycontinually
informedofongoing events of interest. For instance,an officeworker
may want to stay appraisedof the weatheroutside, the traffic
situation for the ride home, howcertainstocksare performing,or how
well a favoriteteamis playing. While peoplemay want to
maintainawarenessof suchinformation,orperhapsevenmonitorit
intermittently, such awarenessideally should notdistractthemfrom
their primarywork or task.
A variety of information communicationdeviceshave
beendevelopedto help peoplemaintaina senseof casualawarenessof
interestinginformation. Theclassicexamplesof thesetypes of devices
are emailalerts,loadmonitors,andstocktickers. More recently,similar
displays use visual and audio presentationmethods to show news,
weather, sports, personaldata, and other information in a small
portion ofthe desktop(Greenberg, 1996; McCrickard, 1999;Zhao &
Stasko, 2000). Also becoming prevalentare
off-the-desktopinterfacesthat use objects in theenvironment and
changesin lighting or backgroundnoiseto communicateanything from
network traffic totraffic in the hallways (Ishii & Ulmer, 1997;
Heineret al., 1999).
Our focus in this article is a set of
peripheralcommunicationtechniquesusedon computerdisplaysthat we
call peripheral displays. Typically, peripheraldisplaysusevery
little screenreal estate,but they stillattemptto convey a fairly
largeamountof information.Often, this translatesinto someuse of
animation tocycle throughitemsof interestvia scrolling or
fadingtechniques.
While animationhas beenshown to be a strongperceptive attention
draw that consequently maydistract peoplefrom their primary task
(Ware et al.,1992), it has also proven to be an effective way
toshow large amountsof information in a small space
(Robertsonet al., 1993). Researchershave
speculatedthatsmoothanimationswould not beoverly
distracting(Fitzpatrick et al., 2001), and organizations
likeYahoo,ESPN,andAOL provide tickering and
fadingdesktopdisplaysthatshow
continuouslyupdatednewsheadlines,stockquotes,sportsscores,weatherreports,and
the computeractivity of friends. Thereare eventoolkits
thathelpenableprogrammersto includetheseandsimilar techniquesinto
their interfaces(Fitzpatricket al., 1998; McCrickard&
Zhao,2000).
While numerousstudieshave examinedpeople’swillingness to use
peripheraldisplaysin maintainingawareness(for example (Parsowith et
al., 1998;McCrickardet al., 1999)),relatively little
researchhasbeenconductedto understandbetter the
informationcommunicationversusdistractiontradeoff for
differenttechniquesof peripheralcommunication.Our goal isto explore
the balancebetweendistraction, reaction,and comprehensionfor
different animatedperipheraldisplays via empirical evaluations of
realistic
butcontrolledsituations.Thispaperdescribesseveralsuchevaluationsthat
asked participantsto searchhypertextspacesfor answersto a series of
questionswhilecompletingactivitiesandansweringquestionsbasedoninformationin
peripheraldisplays.
2 RelatedworkSomeof theearliestevaluationsof
constantlychangingdisplaysexaminedtheperceptibilityandreadabilityofrapid
serial visual presentations(RSVPs) of
letters,strings,andwords.Fosterfoundthatparticipantscouldcorrectly
identify about four out of six words in asentencewhen rapidly
presenteda word at a time inasinglevisuallocation(Foster,
1970).Juolaalsofoundthat comprehensionof information was
comparablewhenpresentedasRSVPsandin multi-line paragraphformat
(Juola et al., 1982). In some of the firststudiesof
smootheranimatedeffects, Duchnicky andKolersperformedaseriesof
experimentsexaminingthe
-
readabilityof text scrolledon visual displayterminalsas a
function of window size (Duchnicky & Kolers,1983). They
foundthat largerdisplaystypically led tofasterperformanceon
readingtasks. A study led byGranaasfound that in
scrolleddisplays,larger jumps(four to tencharacters)ledto
bettercomprehensionthansmallerjumps(oneto two characters)(Granaaset
al.,1984).KangandMuter, in comparingatickeringeffectto a
non-animatedRSVP effect, found no differencein comprehensionfor a
readingtask (Kang & Muter,1989). Theseexperimentsaddressedmany
importantfactors that we explore further in our
research,includingdifferentinformationaltasks(recognitionandcomprehension),differentsizeddisplays,anddifferentwaysto
changethedisplay.
All the previously mentioned evaluationsconsideredthe readingof
small animateddisplaysasthesoletaskof theparticipant.However, in
thecaseofperipheraldisplays,participantswould be performingsome
main task with attention to a small animateddisplaypartof a
secondarytask. Oneexperimentwiththis type of dual-taskscenariowas
conductedwithOwnTime,a
peripheraltimespacemanagementsystemthatalertspeoplewhenvisitorsarewaitingto
meetwiththem(Rodensteinet al., 1999). The study found thatOwnTime
visitor interactionswere lessintrusive thandirect engagementfor
participantsperforming recallandcomprehensiontasks. The researchof
Bartrametal consideredthe effectivenessof using motion cuesto draw
attention(Bartramet al., 2001). They foundthatmotion
cuesoutperformstaticrepresentationsandthat certaintypesof
motionsaremoredistractingandirritating thanothers.
In other work, Maglio and Campbellperformedaseriesof
dual-taskexperimentsin which participantsperformeddocumentediting
taskswhile a peripheraldisplay showed news headlineslater usedto
answerquestions(Maglio & Campbell,2000). Theperipheraldisplays
included a continually scrolling displaythat jumped five pixels per
step, a start-and-stopscrollingdisplaythatbriefly
pausedwheneachheadlineappearedon the screen, and a fading display
thatincreasedthe brightnessof the text to make it visible.They
found no difference in the communicationabilities of different
peripheraldisplays(as measuredby how well information is
remembered). Also, allof the animatedperipheraldisplayswere found
to bedistractingto themaintaskof
documentediting,thoughthestart-and-stopdisplaywastheleastdistracting.
Researchon the effectsof InstantMessaging(IM)notificationson
desktopcomputertasksfound that IMtypically was disruptive to
primary tasks,particularlyso for fast,stimulus-driven
searchtaskssimilar to theonesin the Maglio experiments(Cutrell et
al., 2001).However, IM does not use smooth animation in
itsupdates,which may have excaberatedthe distraction.Our
studyexaminedwhethera slower, semantic-basedsearchtask is affected
by various smoothperipheraldisplays, and whether the peripheral
displays caneffectively communicateinformationto users.
3 ExperimentsTo examine whether animated displays
impactinformation acquisitionwhen maintainingawareness,
two empiricalevaluationswereconducted.Participantswere asked to
completea seriesof browsing taskswhile
simultaneouslykeepingabreastof a peripheraldisplay showing
constantlychangingnews, weather,stock, and sports information. We
utilized threeperipheraldisplaysin theseexperiments: a
tickeringdisplaythathorizontallymovesinformationacrossthescreen,a
fading display that graduallyfadesbetweenpiecesof information, and
a RSVP-style“blast” thatswitchesbetweenitemsin the displaywithout
smoothanimation. For the tickering effect, we employed
asmoothanimationthatrepeatedlymovesthetext apixelat a time in an
attemptto minimize distraction. Theearly
previously-describedstudies typically tickereda display by several
charactersat a time (Duchnicky& Kolers, 1983; Granaaset al.,
1984; Kang &Muter, 1989), and even Maglio and Campbell’s
5-pixel jump when scrolling createsa jerky effect
thatmayhaveresultedin unnecessarydistraction(Maglio
&Campbell,2000).Priorwork hasnotedthatpeopletendto
performbetteroncertaindecision-makingtaskswithsmootheranimations(Gonzalez,1996).
We suspectthatsmoothanimationsmayproveto
belessdistractingthantheonesusedin prior work.
Figure1: Layoutof theexperimentalenvironmentexperiencedby
participants.At thecenteris thebrowser
usedby theparticipantsin theexperiment.At thetopof thescreenis
thefadeperipheraldisplaythatcyclically showed
thestateof severaltypesof information.At thebottomis
theareausedfor monitoringactivities. After eachround,the
screenclearedexceptfor a
questionareawheretheawarenessquestionswerepresented.
Participantsusedthe information presentedin theperipheraldisplay
to completeshort-termmonitoring-style awarenessactivities
(monitoring activities) andto answer longer-term knowledge-gain
questions(awarenessquestions). The experimentsconsistedofseveral
rounds (six in the first experiment, eight inthe
second),eachconsistingof four browsing tasks,two monitoring
activities, and up to five awarenessquestions. The layout of the
information on thecomputerscreenis in Figure 1. Motivationsfor
ourexperimentalchoicesfollow.
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3.1 Browsing tasksIn performing the browsing tasks,
participantsuseda simple browser and hypertext pages. The
browserconsistedof a textual information area containinga number of
condensedpages from World WideWeb sites. The text-only information
areacontainedhighlighted, underlined links that pulled up
otherpageswhenclicked with the mouse. The participantsnavigated the
information spaceby clicking on thelinks andby usingthe
forwardandbackbuttons. Thebrowsing taskswere non-trivial: the
participantshadto readandnavigatethrougha hypertext spaceto
findcertain information in the pages,enter it into a
boxconnectedwith the browser, and press a button tocontinue.
To minimize the typing required,all solutionstobrowsing
taskquestionswerenumerical(for example,“In what year was Mount
Rushmorecarved?”) If
anincorrectanswerwasentered,theinterfacebeepedandtheparticipanthadto
continueworking on theproblemuntil
thecorrectanswerwasentered.Whenthecorrectanswerwasentered,theparticipantcouldproceedto
thenext browsingtask.Theorderin which
browsingtaskswerepresentedwasheldconstantfor all participants.
3.2 Monitoring activitiesWhile performingthe browsing tasks,the
participantsusedinformationin theperipheraldisplayto completea
setof monitoringactivities andto answera
seriesofawarenessquestions.Theperipheraldisplaycyclicallyshowed
instancesof different types of information,suchas a sportsscore,a
stock quote,and a weatherreport. Each instancewas updatedfrequently
butirregularly as it often is in real life. Participantswere asked
to pressa button when the informationin the peripheraldisplay
matchedsomecriteria (forexample,“Whenthetemperaturedropsbelow
35,pressOK1.”) The informationthat wasselectedfor displaywas
interestingbut rarely vital, and the informationaloccurrencesthat
were selectedwere chosenbecausethey mightspurauserto
performsomereal-lifeactivity,suchasbringing in a plant that is
outdoorsor sellingastockthatis performingpoorly.
Eachroundincludedtwo suchmonitoringactivities.Theorderin
whichmonitoringactivitieswerepresentedwas held constantfor all
participants. If the buttonwas pressedat the correct time (that is,
after theneededinformationwaspresented),it wasgreyed outto
alerttheparticipantthatthetaskhadbeencompletedsuccessfully. If the
button was pressedtoo
soon,theinterfacebeepedandthebuttonremainedactive.
3.3 AwarenessquestionsAt the end of each round, the participants
weregiven awarenessquestionsthat asked them to recallinformation
that wasshown in the peripheraldisplay.The questionswere
multiple-answermultiple-choicequestionsthat addressedboth content
and temporalissues. Eachquestionhad four
possibleanswers,allinitially unselected,andtherewasalwaysat
leastonecorrectanswer.
The first questionin eachset listed four typesofinformation and
asked the participant to choosetheonesthathadbeendisplayed.If they
correctlyrecalled
seeinginformation,laterquestionsasked aboutdetailsof it, such as
which news stories appeared,whichstockquotesconstantlyincreased,or
whichsportsteamscoredthe most points. For example,if a
participantcorrectlynotedthatnewsheadlineshadbeendisplayed,later
questionswould presenta list of headlinesandasktheparticipantto
selecttheonesthathadappeared.All of the information was fictional
but realistic, andno attempt was made to intentionally deceive
theparticipants with slightly different information (forexample,a
stockquotethatalmostalwaysincreased).
3.4 Data collectionand evaluationTo
compareperformanceamonggroups,thedependentvariableswere the times
for all browsing tasksandmonitoring activities and the answersto
the post-roundawarenessquestions.The resultswereanalyzedto
determinewhetherdifferencesin certainmeasuresoccurred for
participants in different
conditions(participantsusingdifferenttypesof peripheraldisplaysin
thefirst experiment,andparticipantsusingdifferentsizesandspeedsin
thesecond).
The browsing time is the time from which thebrowsing task and
browser information appearedonthe screento the time when the
participanttyped inthe correctanswerand pressedthe OK button.
Themonitoringtime is thetime from whentheinformationwas first
entered into the cyclic display until
theinformationwasacknowledgedasmatchingthecurrentcriterionvia
abuttonpress.
For the awarenessquestions, the participants’responsesto eachof
the four answerswerecollected.We consideredeach question as being
worth fourpoints: correctlyor
incorrectlyassessingeachpossibleresponseto a question.
A number of different methodscan be used todeterminea
participant’s ability to recall information.The most obvious
measureis to comparethe percentof correct responsesfor the
awarenessquestionsindifferent situations. The percentof
correctresponsesis referredto asthecorrectnessrate.
The correctness rate measure potentially canmisrepresenta
participant’s awarenessof information,however.
Notethataparticipantwhodid not rememberseeinganything in the
peripheraldisplay and left allresponsesunchecked could have a
correctnessrate ashigh or higher than a participant who
rememberedseeingseveral itemsbut wasmistakenaboutwhat
wasseenandcheckedthewrongbox(es).
An alternate measure for determiningresponsivenessis the hit
rate, a term from signaldetection theory defined as the ratio of
correctlyidentified stimuli to the total number of times
thestimulus was presented. The hit rate is typicallyaccompaniedby
the false alarm rate, the ratio ofincorrectstimuli responsesto
thetotalnumberof timeswhenthestimuluswasnotpresent.Sincea
typicalgoalwhenusinga peripheraldisplayis to proactively
recallseeinginformation, it may be better for a participantto be
mistaken about seeing information that wasnot displayedthan to be
mistaken about not seeinginformation that in fact was displayed.
Perhapsapersonwantsto rememberthatastoryoccurred,or thata
tornadowatchis underway, or that a traffic bulletin
-
appeared. The hit rate would reflect the awarenesspotentialof
ananimateddisplay.
In analyzing the results, analysesof variance(ANOVAs) were
performed to check for statisticalsignificance among different
conditions of theexperiments. If the ANOVA revealed a
significantdifference, pairwise t-tests were performed
todeterminewhichconditionsdiffered.
3.5 Experiment 1The first experiment comparedrelative
performancewhenusingfading, tickering, andblastingdisplaysaswell
aswhenno peripheraldisplaywaspresent.
3.5.1 MethodThis experiment focused on three factors:
thepossibility for degradation in performance on abrowsing
taskwhena peripheraldisplaywaspresent,the speed in identifying and
reacting to changesin peripheraldisplays, and the ability to
rememberinformationthatappearedin aperipheraldisplay.
Seventyundergraduatestudentsparticipatedin thisexperiment for
class credit. The experiment wasconductedon
identicalworkstations,eachconnectedtoa 15-inchmonitor with an
optical mouse.Participantswererun in
smallgroups,oneparticipantpercomputer.The experimentwasexplainedto
eachgroupverballyandagainon thecomputerwith examples.
Theparticipantsperformedsix roundsof browsingtasks,monitoring
activities, and awarenessquestions.In eachround,
participantscompletedfour browsingtaskswhile performingtwo
monitoringactivities usingeither a fade, ticker, or a blast
animation. Thespeed with which the information was
displayedcorrespondedto the mean speedsfor each deviceselected by
the participants in a previous study(McCrickard, 2000). While this
resultedin differentratesof informationdisplayfor theanimations,we
feltit wasa morerealisticandecologicallyvalid measureof how
peoplewould usethem. Theticker continuallyshiftedonepixel every 50
milliseconds,while thefadeandblastupdatedtheir entirecontentsevery2
seconds.The fade required500 millisecondsto fade betweenitems,while
theblastupdatedinstantaneously.
At the end of each round, participantsansweredawareness
questions about the information thatappearedin the animateddisplay.
The first questionasked which types of information appearedin
thedisplay. For each correctly-identified instance ofinformation
appearing, two questions about theinformationwereaskedup to a
totalof fivequestions.
As a basecase,onegroupof participants(n � 15)did not have any
animationspresentat any time andassuchperformedonly
thebrowsingtasks.For theothergroups,all participantsexperiencedall
animations,withordersbasedon a latin squaredesign(blast - fade
-ticker (n � 17), fade- ticker - blast(n � 17),or ticker -blast-
fade(n � 21)). A differentanimationwasusedfor eachof thefirst
threeroundswith theorderrepeatedon thelastthree.
3.5.2 ResultsFor the time requiredto carry out the browsing
tasks,therewasnotasignificantimpactdueto
thepresenceofaperipheralanimateddisplay(F
�3 � 58� � 0 � 60,MSE �
46277� 71,p � � 62). Furthermore,thetypeof animationdid not
affect the browsing times (F
�2 � 46� � 0 � 62,
MSE � 25411� 63, p � � 54), (seeFigure2).
1 2 3 4 5 60
50
100
150
200
250
300
350
400
450
Round
Bro
wsi
ng ti
me
(sec
)
No animationBlast Fade Ticker
Figure2: Averagecompletiontimesfor
browsingtasksforeachroundbasedon thetypeof
animationthatwaspresent.Participantsperformedaboutthesameon
thebrowsingtasksregardlessof thetypeor eventhepresenceof
animation.Byshowing theroundsindividually, onecanseethatthereis
notevena trendto suggestthatparticipantsperformedbetterin
certaincases.
In the monitoringactivities, participantspressedabutton when
they noticed specifiedinformation in aperipheraldisplay. Since a
round endedwhen thebrowsing taskswere completed,it was
possiblethatnot all of the monitoring activities were
completed,meaningit waspossiblethat sometypesof
peripheraldisplaysled to more activities
completedthanothers.However, the numberof activities completed(out
of 4possible,blast � 3 � 83,fade � 3 � 80,ticker � 3 � 71)doesnot
dependon the typeof animation,F
�2 � 96� � 0 � 77,
MSE � 0 � 25, p � � 46. That is, it doesnot appearthata
participantis morelikely to identify (or miss)a pieceof
informationwhenusingonetypeof animateddisplaythananother.
While the identification rate when monitoringinformation was not
affected by device type, thetime to react to it was. The times to
completethemonitoring activities differed significantly dependingon
the type of animationsused,with blast requiringan averageof 88.85
secondsin each round for thetwo activities,
fade117.41seconds,andticker 192.93seconds(F
�2 � 52� � 17� 24, MSE � 4528� 75, p �
� 001). Pairwise comparisonsrevealedthat the blastand fade
animationsresulted in significantly
fastermonitoringtimesthantheticker(p ��� 001andp � �
01,respectively) andtherewasa trendtoward
fasterblasttimesthanfade(p ��� 09).
For the awarenessquestions,Figure3 summarizesthe resultsusingthe
threemetricsdescribedearlierformeasuringperformanceon the
awarenessquestions:correctnessrate,hit rate,andfalsealarmrate.
While the correctnessrate for ticker was slightlyhigher than
that for fadeor blast, suggestingthat thetickermaybebetter,
thedifferencewasonly marginallysignificant,F
�2 � 96� � 2 � 62, MSE � 0 � 02, p � � 08. In
-
turningto thehit rate,therewasasignificantdifferenceamonghit
rates.Thehit ratefor ticker washigherthanthat for
fadeandblast,F
�2 � 96� � 3 � 87, MSE � 0 � 03,
p ��� 03.
Correct Rate Hit Rate False Alarm Rate0
10
20
30
40
50
60
70
Rat
e (p
erce
nt)
Blast Fade Ticker
Figure3: Cumulative correctnessrate,hit
rate,andfalsealarmratefor
theawarenessquestions.Theparticipantshad
a significantlyhigherhit ratewhenusingtheticker.
Onedrawbackof many techniquesthatachievehighhit ratesis thatthey
oftenresultin highfalsealarmratesas well. However, this was not
true in this situationas therewas not a
significantdifferenceamongfalsealarmratesfor blast,fade,andticker,
F
�2 � 96� � 0 � 55,
MSE � 0 � 03, p � � 58.3.5.3 DiscussionOnemight suspectthat
participantswho arenot facedwith ananimationandnotburdenedwith
theadditionalmonitoring activities and
awarenessquestionswouldperformsignificantlyfasteron the browsing
tasks,butthe resultssuggestthat this is not the case. In fact,the
resultsdid not even indicatea trend toward lowertimes in the
caseswhen an animateddisplay is notpresent(seeFigure2). While this
seemsto contradicttheresultsfoundin prior studies(Maglio &
Campbell,2000),recallthattheprimarytaskin thosestudieswereediting
tasksthat requiredparticipantsto perform in-depth readingsand make
corrections. The browsingtasks of this experiment were less
demanding,butbasedon previous studies(Fitzpatrick et al.,
1998;McCrickard,2000)they alsomaybettermatchthetypeof
primarytasksthatauserwouldbedoingwhile usingperipheraldisplays.
The times to complete the monitoring activitiesdiffered
significantly depending on the type ofanimations used. The blast
and fade animationsresultedin significantly fastermonitoring times
thanthe ticker. This result seemsto follow from previousresults
that indicate that moving text is read moreslowly than non-moving
text (Sekey & Tietz, 1982;Granaaset al., 1984).As
thetickeringdisplayreliesonmotionto cycle betweenitemswhile
thefadeandblastdo not, it seemsreasonablethat theticker would
resultin slower performance,particularly if the participantswere
readingthe displaysto identify information thatthey
weremonitoring.
In analyzing the responsesto the awarenessquestions,the
correctnessand hit ratesfor the threeanimation types suggestedthat
the ticker may bebetter. This does not contradict the results
notedpreviously indicating that moving text was moredifficult to
readthannon-movingtext. Thenatureof themonitoring activities and
the awarenessquestionsarequite different. In fact, otherstudieshave
shown thatcomprehensibility, unlikereadingspeed,is not affectedby
motion (Kang & Muter, 1989), so it is reasonableto expect the
results to differ. The implication oftheseresultson the
developmentanduseof animateddisplaysis clear:if thegoalis to
identify itemsquickly,an in-place display like a fade or blast
should beused,while if the goal is to
increasecomprehensionandmemorability, a motion-baseddisplaylike a
tickershouldbeused.
3.6 Experiment 2The previous experiment suggestedthat there
aredifferencesin performancewhen using the fade andticker
displays.In a follow-up experiment,we wantedto explore whether
certain factors, namely displaysize and animation
speed,impactedperformanceinany way. Perhapsmaking the display area
largerwould result in faster recognition times and allowthe
awarenessquestionsto be answeredwith greateraccuracy, or perhapsa
slower speedwould be lessdistracting,resulting in lower times on
the browsingtasks.
3.6.1 MethodNinety-oneundergraduatestudentsparticipatedin
thisexperiment for class credit. The materials
andprocedureweresimilar to theonesusedin thepreviousexperimentwith
thedifferencesdescribedhere.
A between-subjectssize and speedcondition
wasadded.Theparticipantswerepresentedwith a displayhaving oneof
threecharacteristics:normaldisplaysizeand animationspeed,normal
size but slow speed,orsmallsizebut normalspeed.
The normal displayswereusedas the comparisonpoint for
thesmallandslow displays.Normaldisplaysusedlarge display areasand
fast speeds,thoughbothwell within the rangesof
sizesandspeedsselectedbyparticipantsin a previous study
(McCrickard, 2000).Both the fadeand ticker had a width of 1180
pixels(about160 characters)with a heightof oneline.
Thissizewaschosenbecauseit fits nicely alongthe top orbottom of the
screenand becauseit is large enoughto hold long streamsof
information (such as newsheadlinesandweatherbulletins) in their
entirety. Theticker speedwas at the upper rangeof the
possiblespeedsfor theplatform,onepixel per20 milliseconds.The fade
cycle step had a 100 millisecond delaybetweeneachof five stepswith
a three-seconddelaybeforethenext fade.
Thesmalldisplayuseda smallerareabut thesamespeedas the normal
display. The fade and tickerwidth was more than halved to 840
pixels (about70characters),smallenoughto fit abovea
singleterminalwindow. Thisreductionin sizemeantthatmoststreamsof
informationcouldnot beshown in their entirety.
The slow displaywas the samesizeas the normaldisplay, but
slower. Thespeedwaschosento beat the
-
slow end of the rangeselectedby participantsin thepreviousstudy.
Thetickerupdatedatarateof onepixelevery 140 milliseconds. The
fadeupdatedone shadeevery150millisecondswith adelayof 9
secondsbeforethenext fade.Thesizefor thewidgetswasthesameasin
thenormaldisplay.
We focusedon resultsfrom pairs of displaysthatdiffered in
eithersizeor speedbut not both. That is,we did not examinethe
differencesbetweenthe slowand the small displaysbecausethey
differed in
bothspeedandsize.Insteadwefocusedonthenormal-smallversusnormal-slow
pairingsso that any differencesinperformancecould be attributed
more confidently toonefactor.
Theawarenessquestionsalsodifferedfrom thefirstexperiment. In the
first experiment,the first questionasked participantsto select the
types of informationthat were displayed, then for each case where
theparticipantstatedcorrectly that a type of informationwas
displayed, two additional questionswere askedaboutthat
information,thefirst relatingto contentandthe secondrelating to
order. In this experiment,eachparticipantansweredall five of the
questions. Thischangeseemedreasonablesincea cuesuchasa wordor
phrasein aquestioncanaid retrieval from memory.
The numberof roundswas increasedfrom six toeight. It
wasdeterminedthatparticipantswouldstill beable to completethe
experimentwithin the requestedhour even with the additionalrounds.
Also, the typeand order of the animationswas changed.
Sincetheblastdisplayresultedin performancesimilar to
thefadedisplayandwasconsistentlyratedasthe
leastfavoritedisplaybyparticipantsin thefirst experiment,it
wasnotusedin the
secondexperiment.Participantsalternatedbetweenusingfadeandticker in
eachround,with onegroup startingwith fade,then twice using ticker
thenfadeagainandrepeating(fade,ticker, ticker,
fade),andtheothergroupswappingtheorderstartingwith ticker.
In summary, thereweresix groupsof
participantsdifferentiatedbyanimationclassification(normal,slow,or
small)andstartinganimation(fadeor ticker). Eachgroup had 15
participantsexcept the slow fade-firstgroupwith 16
participants.
3.6.2 ResultsFor the cumulative time required to complete
thebrowsing tasks,changesto the size and speedof
theanimateddisplaydid not leadto differencesfor eitherthe fadeor
the ticker, (for fade: normal � 2999� 03,slow � 2890� 87, small �
3131� 10 with F � 2 � 88� �0 � 58, MSE � 765992� 08, p � � 56; for
ticker: normal� 3036� 83, slow � 3036� 93, small � 3079� 45 withF�2
� 88� � 0 � 01,MSE � 997900� 50, p � � 99).For monitoring
activities, the resultsshowed that
changesto thenatureof
theperipheraldisplayaffectedperformancewhen using the ticker (F
�2 � 29� � 5 � 23,
MSE � 40792� 90,p � � 01)but not thefade(F � 2 � 66� �1 � 62,
MSE � 12712� 58, p � � 21). We consideredpairwise t-tests to
determinewhere the significancelay. Did the size of the display
affect performanceon monitoring activities? Figure 4 suggeststhat
itdoes. Whenusingthe ticker, the time to completethemonitoring
activities wassignificantly different basedon thesizeof
theanimateddisplay, p � � 02.
Fade Ticker0
20
40
60
80
100
120
Mea
n m
onito
ring
time
(sec
)
LargeSmall
Figure4: Meancompletiontimesfor eachmonitoringactivity
whenusinglarge(normal)andsmalldisplays.Fortheticker,
smallerdisplaysresultedin significantlylower
timesthanlarger.
Did thespeedof thedisplayalsoaffectperformanceon
monitoringactivities whenusing ticker? For eachdisplaytype
themonitoringtimesappearto have beensimilar regardlessof
speed(fade41.1and45.7seconds,ticker 102.3 and 100.7 secondsfor the
fast and slowdisplays,respectively). Theanalysisverifiesthat
therewasno significantdifference:for the ticker, the
t-testresultedin p � � 79,for thefade,p � � 87.
For theawarenessquestions,thecumulativehit ratewhenusingthe
fadewasvirtually identical regardlessof display size or speed(with
normal 67.4%, slow66.8%,small68.3%andF
�2 � 88� � 0 � 09,MSE � 0 � 02,
p � � 92). However, when using the ticker, the hitratesdid
differ significantly(with normal68.2%,slow61.3%, small 68.3% and
F
�2 � 88� � 3 � 26, MSE �
0 � 02, p � � 04). A t-test revealedthat the
differencebetweenthe normalandslow displayswassignificant(p � �
03),while thedifferencebetweenthenormalandsmall displayswasnot (p �
� 98). As in the previousexperiment,thefalsealarmratedid notdiffer
regardlessof display size or speedfor either the fade (normal18.4%,
slow 16.8%, small 20.8%; F
�2 � 88� � 2 � 24,
MSE � 0 � 01,p � � 17)or theticker(normal19.3%,slow18.8%, small
19.7%; F
�2 � 88� � 0 � 10, MSE � 0 � 01,
p � � 91).3.6.3 DiscussionAs wasnotedin
thepreviousexperiment,for thetypeorpresenceof ananimateddisplay,
neitherthedisplaysizenor the animationspeedseemedto negatively
impactthetime requiredto completebrowsingtasks.
Users did not complete monitoring tasks morequickly with a fast
animation than a slow one.One possibleexplanationfor this result is
that eventhough the increasein speedgives
participantsmoreopportunitiesto seethe
information,eachopportunityis shorter becausethe information
disappearsmorequickly. Thesetwo factorscould balanceout to resultin
similarmonitoringtimes.
Althoughchangesin thespeedof thedisplaydonotseemto affect
monitoring times, changesin the sizedo. A smaller display results
in significantly fastermonitoring times when using the ticker, and
there is
-
a trend toward fastertimes when using the fade(seeFigure4).
While thisresultis notimmediatelyintuitive,it does seemto
correspondto the model that
mostpeopleuseduringperipheralmonitoringactivities: theyare focused
on a primary task while occasionallyglancingat
theperipheraldisplay. As notedby Rayner(Rayner,1978),only alimited
numberof characters(upto 20) canbe processedin a quick glanceat a
display.The greaternumberof charactersin a larger displaymay make
it more difficult for a personto find thedesiredinformationwith
aquick glance.
While the size of the display seemedto impactperformanceon the
monitoring activities, it doesnot seem to impact performanceon the
awarenessquestions. The participantsperformedequally wellon the
questionswhetherusing the larger or smallerdisplay. One reason the
display size may makea difference in answeringthe questionsbut not
inperformingthe monitoringactivities lies in the natureof the two
tasks. Whereasthe monitoring activitiesrequire only a quick glance,
the ability to answerquestionsrequiresa morecarefulreadingof the
entireinformation entry. In fact, it is somewhat surprisingthat the
larger display did not show better resultsonthe
awarenessquestionsthan the smallerone, thoughthis maybebecausethe
smallerdisplaywasstill largeenoughto containmost or all of the
information formany of theinformationentries.
The speed of the tickering display seemedtoimpact performanceon
awarenessquestions. Aslower animation resultedin poorer
performanceonthe questionsthan a fasterone,
perhapsbecausetheparticipants too often glanced up to see the
sameinformation. This resultis consistentwith theGranaaswork
thatshowedfastertickers(with largerjumpsin thescrolling)resultedin
bettercomprehensionthanslowertickerswith smallerjumps(Granaaset
al., 1984).
In comparing performance on the
awarenessquestionsbetweenexperiments, the result from
thepreviousexperimentwasnot replicated:the ticker didnot resultin
improvedperformanceover thefade.Thismay be relatedto the amountof
information on thescreen.Thetickersin this
experimentwereaslargeorlargerthantheonesin thefirst
experiment,resultinginfarmoreinformationonthescreenatany
giventimeforthe ticker, especiallycomparedto the fade. The shapeof
the displaymay alsobe a factor. The fadedisplayin the first
experimentwasa three-linedisplay, whilein thesecondit wasa
one-linedisplayidenticalin sizeand shapeto the ticker. It is
possiblethat multi-linedisplaysaremoredifficult to
processandcomprehendin a glancethan single-linedisplays. Futurework
isnecessaryto testthathypothesis.
4 GeneraldiscussionThegoalof theempiricalevaluationswasto
explorethebalancebetweendistraction,reaction,comprehension,and
memorability when using peripheral animateddisplays. The first
experiment showed that fading,tickering, and blasting peripheral
displays did notsignificantly distract users from a primary task
yetcould effectively communicateinformation. The typeof animation
impacted performanceon monitoringactivities and awarenessquestions.
The second
experimentshowedthatchangesin
sizeandspeedalsocouldimpactperformanceon monitoringactivities
andawarenessquestions.
The following recommendationscan be derivedfrom theresultsof
theseexperiments:
Animated displays can be used in the peripherywith minimal
negative impact on certain primarytasks. While other work (Maglio
& Campbell,2000)seemsto
suggestotherwise,bothexperimentssupportedthis claim.
Thedifferencemayresultfromaprimarytaskthatis lesscognitively
demandingandsmoother, sloweranimations.
In-place displayssuchasfadeand blast arebetterthan
motion-baseddisplays lik e ticker for rapididentification of items.
Participantswere able tocompletemonitoring activities more quickly
whenusingthe fadeandblast thanwhenusingthe ticker.This seemsto
extendprior resultsthat indicatedthatmoving text is moredifficult
to readthanstatic text(Sekey & Tietz,1982; Granaaset al.,
1984). Motion-based displays such as ticker are better
than in-place animations for comprehensionand memorability.
While in-place displays aidrapid identification, on the
awarenessquestionsparticipantswho used the ticker obtaineda
betterhit rateanda marginally bettercorrectnessratethanthosewho
usedthe blastand the fade. At the veryleast,this suggeststhat if it
is essentialto rememberinformation at the risk of
mis-rememberingit, amotion-baseddisplayshouldbeused.
Small displays result in faster identification ofchanging
information. This may be relatedto theamountof information that a
viewer can read in aglance. Larger displays may make it difficult
toobtaindesiredinformation. Fast displaysare better than slow for
establishing
comprehensionand memorability. This wasnotedin
thesecondexperimentfor thetickeringanimationandmayberelatedto
theamountof new informationthat is available in a glance. Slower
displaysmaydiscouragepeoplefrom lookingat themoften.
5 Conclusionsand futur e workThe results of the experiments and
the growingpopularity of peripheraldisplayssuggestthat peoplecan
use them to help maintain awareness. Besidesproviding
immediateinformation, smoothlyanimatedchangesto the display can be
small, subtle, andpredictable,allowing theuserto adaptto
thechangingdisplay to the point where it is less distracting. Itis
necessaryto understandthe trade-off betweentheimportanceof
theinformationbeingcommunicatedandtheresourcesnecessaryto
displayandprocessit.
This researchhas developedan understandingofthenatureof
theawarenessproblemandof how users’wantsandneedsdiffer in
maintainingawareness.It isreasonableto concludethat the useof
animationcanassistin maintainingawarenesswithout
causingunduedistractionin particularsituations.As with
mosttools,peripheralanimationscan be andhave beenmisused,
-
but whenusedproperly, this researchhasshown theyhave
thepotentialto bebeneficial.
The population of participantsin the study wasundergraduatesat a
technicalschool with significantexposure to computers and
interfaces. Furtherstudiesare necessaryto determinethe
effectivenessof peripheral displays for other segments of
thepopulation,suchaspeoplewith morelimited skills andpeoplewith
little computerexperience.Otherongoingwork is examiningwhat typesof
informationarebestsuitedfor display in the peripheryand other
primarytasksthat arenot negatively impactedby the presenceof
peripheraldisplays. As was notedpreviously, theparticular focus of
this work on controlledsituationsallows us to
understandandcompareperformanceforcertainscenarios,but it is also
importantto apply thelessonslearnedin this work to real-world
applications.
AcknowledgmentsThis researchwas partially supportedby Air
ForceOffice of Scientific ResearchGrant F49620-98-1-0362 to Richard
Catrambone. Thanks to GregoryAbowd, Amy Bruckman,Mark Guzdial, Alex
Zhao,and the anonymousreviewers for their assistanceandcommentson
this research.
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