Lec 2UsingSpace

Cogs102A*DistributedCognition

EcologicalPerception

• Asystemsmodelthatasks:Howdoesthehuman/worldsystemaccomplishperception?

• Assumesevolvedperceptualsystemsenableperceiverstonavigate through,andmanipulate,theirenvironments.

• Operationofsystemsgenerate“Invariants”=regularitiesthatemerge wheneverahumanengagesitsvisiblespace

• Sincenaturalfunctionisofprimaryconcern,boththeory&methodaimtomaximize“EcologicalValidity”ofresearch

• Theworldisacluttered,dynamicplaceandperceiversoftenmovethemselves,sothisiswhatweshouldstudy

EcologicalPerception

J.J.Gibson:"EcologicalPerception"

Perceptionastheinteraction

betweenan

activeperceiver

anditsenvironment

EcologicalPerception

Gibsoncommissionedtoresearchhowtodesign

realisticsimulatorstotrainWWIINavypilots

Contemporaryresearchdoneincomplex,real-world

environments,w/subjectssolvingreal-worldproblems

• PROBLEM:• Howdoesanobservergetfromheretothere?• Howdoesitperceiveitsspeedanddirectionofmovement?

• SOLUTION:• Focusondestinationpointandmovesuchthatthe

OpticFlowpatternsymmetricallyexpandsfromthatpoint.

OpticFlow=whenobservermoves,environmentstreamstoorfrom“FocusofExpansion”(FOE)

• OnlyFOE (subject’sfocalpointinenv,towardswhichitismoving)isstationary

• Restofvisualenvironmentexpands asyoumoveforward(towardFOE)

• Similarly,visualenvironmentcontracts asyoumovebackward (fromFOE)

FOE

Thesepointsmoveslowly

Thesepointsmovequickly

OpticFlow=whenobservermoves,environmentstreamstoorfrom“FocusofExpansion”(FOE)

• OnlyFOE (subject’sfocalpointinenv,towardswhichitismoving)isstationary

• Restofvisualenvironmentexpands asyoumoveforward(towardFOE)

• Similarly,visualenvironmentcontracts asyoumovebackward (fromFOE)

• Theacceleration ofexpansion/contractionisdirectlydependentonmover’svelocity

• PointsclosertoFOE willmove moreslowly,

• PointsfartherfromFOE movemorequickly

So,itistheseregularitiesofrelationshipbetweenrateofexpansion/contractionanddirection&velocityofmovementthataretheInvariants inthisactivity.

OpticFlowFunction

• Thus,iffocusondestination(FOE)&movesothatOpticFlow

symmetrically expands...

• 1)Workstogetyouthere

• 2)Enablesyoutoperceiveyourrelativedistancefromallpoints(basedontheirrelativeratesofexpansion)

• 3)Enablesyoutoperceiveyourownvelocity(sinceexpansionratesareafunctionofthis)

• PROBLEM:• Howdoyoukeepfromrunningintothings?• Howdoyoucatchordodgesomethingcomingatyou?

• SOLUTION:• Adjusttrajectory(orreach/grasp)accordingtothe

RateofAngularExpansion(“Tau”)oftheobject.

RateofAngularExpansion

Whenanobjectmovesdirectlyatyou,oryoudirectlytowardit,atagivenvelocity,itsrateofchangeisanInvariant

RateofAngularExpansion

Objectexpands atanacceleratingrateatitapproachesyou

RateofAngularExpansion

Objectexpands atanacceleratingrateatitapproachesyou,contracts atadeceleratedrateasitmovesaway

AngularExpansion– "Tau"

Plus,ifobjectismovingdirectly to/fromyou,itsapparentexpansion/contractionwillbesymmetrical

Rate ofexpansion/contractiondependsonobject'svelocity

AngularExpansion– "Tau"Rate ofexpansion/contractiondependsonobject'svelocity

But,ifobjectisNOT movingdirectly to/fromyou,itsapparentexpansion/contractionwillbeasymmetrical

• PROBLEM:• Howdoyoudeterminetherelativelocation

(toyou,toeachother)of2objectsasyou(orthey)move?

• SOLUTION:

• Observeinvariantpatternsin“KineticOcclusion”(AKA“Accretion/Deletion”)

KineticOcclusion(AKA"Accretion/Deletion")

Objectthatdeletes (occludes)anotherismovinginfront ofit,ORispositionedbetweenyouanditasyoumove

Objectthatshowsaccretion (becomesmoreandmorevisibleasothermoves)isrevealedasbehind other

KineticOcclusion(AKA"Accretion/Deletion")

Atagivenvelocity,objectsclosertogether changeindeletion/accretionmoreslowly

thanobjectsfartherapart

• PROBLEM:• Howdeterminetherelativesizeandlocationof2objects

whenallyoucanmoveareyoureyes?

• SOLUTION:

• Observerelativefrequency ofthe“TextureGradient”onthesubstratethattheyocclude(hide).

TextureGradients

Man-made Natural

Allsubstrates,naturalorman-made,areperceivedasarepeatingpatternthatincreasesinfrequencyasitrecedes

TextureGradient

Man-made Natural

Invariant:Gradientsbecomehigherinfrequencyasobserver’sfocusmovesfartheraway (lowerfreq asmovescloser)

"Frequency"=#ofCYCLESoftextureperdegreeofVisualArc

TextureGradient

Invariant:Gradientsbecomehigherinfrequencyasobserver’sfocusmovesfartheraway (lowerfreq asmovescloser)

Thisinvariantallowsustojudgedistance&size

ChangeinFrequency=ChangeinDistance

NoChangeinFrequency=NoChangein

Distance

TextureGradient

IfobjectsAandBarethesamesize,ifAoccludesahigherfreq gradientthanobjectBdoes,objectAmustbe

fartheraway thanobjectB

2cycles

4cycles

TextureGradient

Ifobjectsdifferinsize,atthesamedistance,theonethatoccludes

morecycles willbeperceivedaslarger

4cycles2cycles

TextureGradient• Note:Typically,large/closeobjectsLOOM=takeupmoreofvisualfield,

butabovefactorscantakepriority(seeLAB2!)

• So,sizeanddistanceareco-constrainingfactorsinthissystem• (e.g.Asyoumayknow,see...Emmert’s Law Sp=Sr XDp)

TextureGradient

Wecanbefooled intoseeingspacethatisn’tthere,misjudgingsize,etc.byartistswhoexploittheseinvariants

TextureGradient

Wecanbefooled intoseeingspacethatisn’tthere,misjudgingsize,etc.byartistswhoexploittheseinvariants

PlusMotionParallax

SeeLAB2!

Invariants =Regularitiesinhowobjectsinenvmoverelativetooneanother

givenperceiver’sposition,movement&focus

Givenhowfundamental

– i.e.predisposed,well-practiced,vitaltoaccomplishment–

spatialcognitionis,

itisnotsurprisinghowoftenweexploitit’sregularitiesto

makeothercognitivetaskseasier…

Spatialvs.SymbolicProcessing

Shiftfromsymbolictospatial processing

• e.g.SeeSpeedBug fromLecture1

• Pilotsshiftfromusingnumberstojudgingspatialdistancefromneedleondialto“SpeedBug”marker

Track spatial juxtaposition of needle and “bug”

Spatialvs.SymbolicProcessing

Avoidingabstract,symbolicprocedures• e.g.Lave1994

• Askedtoprovide“3/4ofnormaldailyallowanceof2/3cupofcottagecheese”

• Cookfirstmumblesabouthavingtaken“calculusincollege”...

3/4X2/3?

3/4________

2/3 ?

2/3________

3/4 ?

Spatialvs.SymbolicProcessing

Howmuchis3/4ofdailyallotmentof2/3cup?

Voila!

2/3

SpatialAssociations

MemoryPalace• Usespatialsimulationofa“MemoryPalace”asmnemonicdevice

• Easiertorememberitemsassociatedwithdistinct,knownlocations

• “MethodofLoci”– FirstdescribedbyGreekphilosophers,500BC

SpatialAssociations

MemoryPalace

Fourscore&7yearsago dedicated

totheproposition

that.

a newnation,conceivedinliberty

and

allmenarecreatedequal

SpatialAssociations

Chunking• Groupsubsets>feweritemstoremember

CIAFBINCISDOD

vs.

CIAFBINCISDOD

SpatialAssociations

Cache - Putthings“intheirplace”• e.g.Dishes,towelsin

differentcupboards• Especiallywithsimilarthings• Easiertofindwhenneeded

• Organizationthenshapesbehavior• Goto“right”placetoget

Co-Locate withassociated structure• e.g.Cleandishesindryingrack,

dirtystackedoncounterorinsink

SpatialAssociations

Task-DependentOrganization

• Hand-EyeCoordination• Welearntodivergeandcoordinate

ourmodalitiesofattention

• SeeupcominglectureonTRIADICDEVELOPMENT

• Primacyof“Praxic Space”• Time-lapserevealsarea

(ventral,medial,headtolap)ofmosthandactivity

Task-DependentOrganizationACCESS

Withinreach• e.g.CookbringsallingredientsandtoolstoWorkspace (“Praxic”space)

• Allowseasy,efficientaccess,insometimestime-sensitiveprocedures

Task-DependentOrganizationACCESS

Re-Orient forbetter(safer)access• e.g.Turnhandlesofcookingpotstoward(cooler)edgesofstove

sowon’tgettoohottohandle

Task-DependentOrganizationACCESS

Locatetoolswhereactivityoccurs foreaseofaccess• e.g.Keysneardoor,sinceneedwhenleavinghouse

Task-DependentOrganizationACCESS

Locateobjectswhereactivityoccursforeaseofaccess• e.g.Productionlinew/binsofparts

Task-DependentOrganizationORDER

ArrangeaccessbasedonORDERelementswillbeused• e.g.Putobjectsinaline,intheorder theyareneeded

• Nextiseasiesttoreach,Loomsasapproach

Task-DependentOrganizationORDER

• Notetradeoffduringassembly• Canlayoutinorder or forlocationused,butnotboth…

...unlessadditionalinfoprovided

Task-DependentOrganizationORDER

Co-Locate withassociated structure• e.g.Baggerseparatesitemsbysize,weight,fragility

toorganizeeffectivebagging

Task-DependentOrganizationORDER

• e.g.Hierarchical sorting allowssearchtobe…• Limited toonelevelatatime• Directed torelevantdetails

Task-DependentOrganizationMARKING

Co-Locate withassociated structuretoinform• e.g.Oncemeasure&cutbutter,layknifeoncutsection

toID,later,whichwasmeasuredpart

Task-DependentOrganizationMARKING

CanalsousespacetomarkwhatNOTtodo• e.g.Atasettable,donotdohomework• e.g.Workerslayragacrosshothandles:Beware!

SpatialAssociations

Unusualplacement• e.g.Pillbottleonkeyboard• Especiallyincommonlyengagedlocation• Surprisemarksas“special”,noteworthy

• Increases”Salience"• Likelinessofbeingnoticed

Tothetrees!