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htmlDistinguishingbetweenparallelandserialaccountsofmultipleobjecttrackingPiersHowe,MichaelCohen2,YairPinto,andToddHorowitzAbstractHumanscanattentionallytrackmultiplemovingobjects.
IsthisaccomplishedbyattendingtoalltheobjectsatthesametimeordoweattendtoeachobjectinturnWeaddressedthisfundamentalquestionusinganovelapplicationofthesynchronous-asynchronousparadigm.
Participantsviewedfourgroupsofdots,eachgroupcontainingfourdots,eachgrouplocatedinitsownquadrant.
Duringthetrial,whichlastedsevenseconds,eachgroupofdotswouldrotatearoundthecenterofitsquadrant,90degreesatatime,withapausebetweenrotations.
Thedirectionofsuccessiverotationswasrandom.
Participantstrackedonedotineachgroup.
Inonecondition,allgroupsrotatedsynchronously.
Intheothercondition,thegroupsrotatedasynchronouslysothatatanygiventimeonlyhalfthegroupswererotating.
Ifobserverstrackdotsserially,thentheasynchronousconditionshouldyieldsuperiorperformancesincefewerdotsmovesimultaneously.
Conversely,astandardparallelaccountpredictscomparableperformanceinthetwoconditions.
Surprisingly,wefoundthatperformancewasactuallybetterinthesynchronousconditionthanintheasynchronouscondition,disconfirmingaserialaccount.
Wespeculatethatthemotiononsettransientsintheasynchronousconditioninvoluntarilyswitchedattentionbetweendots,therebydisruptingtheparalleltrackingmechanism.
Thereisevidencethattrackingoccursindependentlyineachcerebralhemisphere(Alvarez&Cavanagh,2005,PsychologicalScience,16,637).
Whilethismightexplainwhydotsindifferentvisualhemifieldscanbetrackedinparallel,whenweconfinedallthedotstojustonevisualhemifield,performancewasstillgreatestinthesynchronouscondition.
Infact,whenallthedotswereconfinedtojustonequadrant,performancewasstillinconsistentwithaserialaccount.
Weconcludethatmultipleobjecttrackingisachievedinparallelacrossthevisualfield.