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Psychological Research (2007) 71:265–276 DOI 10.1007/s00426-006-0082-2

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ORIGINAL ARTICLE

Updating representations of learned scenes

Cory A. Finlay · Michael A. Motes · Maria Kozhevnikov

Received: 15 November 2005 / Accepted: 11 March 2006 / Published online: 19 October 2006© Springer-Verlag 2006

Abstract Two experiments were designed to comparescene recognition reaction time (RT) and accuracy pat-terns following observer versus scene movement. InExperiment 1, participants memorized a scene from asingle perspective. Then, either the scene was rotatedor the participants moved (0°–360° in 36° increments)around the scene, and participants judged whether theobjects’ positions had changed. Regardless of whetherthe scene was rotated or the observer moved, RTincreased with greater angular distance betweenjudged and encoded views. In Experiment 2, we variedthe delay (0, 6, or 12 s) between scene encoding andlocomotion. Regardless of the delay, however, accu-racy decreased and RT increased with angular dis-tance. Thus, our data show that observer movementdoes not necessarily update representations of spatiallayouts and raise questions about the eVects of durationlimitations and encoding points of view on the auto-matic spatial updating of representations of scenes.

Introduction

Often people Wnd themselves coming upon a familiarscene or even a recently viewed scene from an orientation

that diVers from their orientation when they initiallyencoded the scene (e.g., when one is forced to detourfrom a previously taken route). Several scene recogni-tion studies suggest that an observer’s mental represen-tation of a scene is often viewpoint-dependent (e.g.,Christou & BuelthoV, 1999; Diwadkar & McNamara,1997; Shelton & McNamara, 2004; for an exception, seeMou & McNamara, 2002), that is, oriented to the per-spective that the observer had when studying thescene. For example, Diwadkar and McNamara (1997)had observers Wrst memorize a scene and then viewrotated pictures (from 0° to 345°) of the same scene orpictures of diVerent scenes (i.e., the spatial conWgura-tion of objects in the learned scene were rearranged).Response times to recognize whether the pictures wereof the same or a diVerent scene increased with angulardistance between the orientation of the memorized andjudged scenes.

Although there is evidence that representations ofscenes are viewpoint-dependent, several studies sug-gest that processes associated with locomotion, even ifthe person is blindfolded, automatically update theperson’s representation of the scene to be spatiallyconsistent with the person’s perspective of the sceneafter moving (Farrell & Robertson, 1998; Farrell &Thomson, 1998; Reiser, 1989). Rieser (1989), for exam-ple, had observers memorize the locations of nineobjects that surrounded them, then rotate within thearray of objects to a target facing direction while blind-folded, and Wnally point to a target object from thatfacing direction. The observers were equally fast atpointing to targets after rotating to the new orienta-tion, regardless of the magnitude of the rotation, asthey were when pointing to targets from the encodingorientation. Thus, the data suggest that the observers’

C. A. Finlay · M. A. MotesDepartment of Psychology, Rutgers, The State University of New Jersey, Newark, NJ, USA

M. Kozhevnikov (&)Department of Psychology, George Mason University, 4400 University Drive, MSN 3F5, Fairfax, VA 22030, USAe-mail: [email protected]

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representations were transformed during the rotationto match the new orientation. Farrell and Robertson(1998) essentially replicated Rieser’s (1989) Wndings,but also showed that when instructed to ignore therotation, RT and error increased with angular distance,thus showing that the eVects of updating are automaticin that they cannot be ignored (but see Waller, Mon-tello, Richardson, & Hegarty, 2002).

Rather than directional judgments, Simons andWang (1998), Wang and Simons (1999) studied theeVects of observer movement and scene movement onscene recognition. On each trial, observers wereshown a 5-object scene, followed by a brief delay.Observers were then shown the same scene exceptthat one of the objects was moved to a diVerent loca-tion, and the observers verbally reported the name ofthe moved object. Across a series of studies, observ-ers were less accurate at identifying scene changeswhen they remained at the encoding station but thescene was rotated (47°) from the encoding orientationthan when the observers remained at the encodingstation and the scene remained at the encoding orien-tation. However, observers were equally accurate atidentifying scene changes when they moved (47°)from the encoding station but the scene remained atthe encoding orientation and when they moved (47°)from the encoding station and the scene was alsorotated (47°) from the encoding orientation (orslightly more accurate in the former condition, Wang& Simons, 1999, Experiment 1). Thus, according tothe spatial updating hypothesis, the observers’ mentalrepresentations of the encoded scenes were spatiallyupdated as the observers moved around the scene,but such spatial updating did not occur when thescenes were rotated but the observers remained at theencoding station.

Simons and Wang (1998, Experiment 2; Wang &Simons, 1999, Experiment 1), however, also reporteddata that were inconsistent with a strict spatial updat-ing model. They reported lower change detection accu-racy when observers moved from the encoding stationand the judged scenes remained at the encoding orien-tation than when observers remained at the encodingstation and judged scenes that remained at the encod-ing orientation. Although Simons and Wang arguedthat this eVect of observer movement on scene recogni-tion accuracy was “weaker than the eVect of scenerotation,” this particular comparison is an essentialcomparison for testing whether full spatial updatinghas occurred. If fully updated, then observers shouldbe equally accurate and equally fast when judgingscenes following movement as when they remain sta-tionary (e.g., Rieser, 1989).

Other studies have also failed to Wnd support for astrict, automatic, spatial updating model (Mou, McNa-mara, Valiquette, & Rump, 2004; Motes, Finlay, &Kozhevnikov, in press). Mou et al. (2004), for example,had observers learn a scene, move into the scene, makean orientation change (either 0°, 90°, or 225°), andWnally, close their eyes and point to a target. The blind-folded observers were slower at pointing to targetsafter rotating 225° from the orientation in which theymemorized the scene than when they did not make ori-entation changes or when they made 90° changes.Thus, the observers’ representations were not updated,at least not fully updated, following the 225° orienta-tion changes.

Motes et al. (in press) had observers learn a spatiallayout of 11 objects from a single perspective. Afterlearning the layout, observers judged whether subse-quently presented scenes were the same as or diVerentfrom the encoded scene (half of the trials had the sameconWguration as the encoded scene; half had diVerentconWgurations in that the positions of two objects wereswitched). For the scene recognition judgments, half ofthe observers moved to one of ten viewing stations,from 0° to 360° in 40° increments, from the encodingstation while the scene remained stationary, and theother observers remained at the encoding station butthe scene was rotated to one of nine orientations, from0° to 320° in 40° increments, from the encoding orien-tation. Regardless of whether the scene was moved orthe observer moved, scene recognition RT increasedwith angular distance between the encoded and judgedviews and performance between the groups did not sig-niWcantly diVer for any of the angular distances. Thus,the data suggest that the observer movement group’srepresentations of the scene were not automaticallyupdated as they moved around the scene.

These failures to Wnd evidence of automatic spatialupdating might have been due to observers relying onallocentric rather than egocentric representations whenjudging the scenes. According to Mou et al. (2004), theallocentric, environment-based system holds enduringrepresentations of relatively familiar environments. Thesystem codes the geometry of the surroundings and thespatial relations of objects with respect to other objects.The allocentric system also codes self-to-object spatialrelations, but the self is merely treated as another objectin the environment. The egocentric system, on the otherhand, holds transient representations of one’s relativelyimmediate environment. The system codes the spatialrelations between oneself and objects in the environ-ment with respect to one’s prominent body axes: left–right, front–back, above–below. Furthermore, Mouet al. suggested that egocentric representations begin to

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fade with delays as brief as 10 s between encoding andlocomotion, and thus, their maintenance requires on-line sensory feedback. Mou et al. further argued thatautomatic spatial updating requires these egocentricrepresentations and that observers would be forced torely on enduring, allocentric representations (if avail-able) if the egocentric representations fade.

Observers in our previous study (Motes et al., inpress) memorized a single scene at the start of theexperiment, and they were required to rely on theirmemory of that scene throughout the duration of theexperiment (i.e., they were not explicitly given theopportunity to refresh their memories of the scene).Therefore, the observers’ egocentric representationsmight have faded over the duration of the scene recog-nition trials. If so, observers were then forced to useenduring, allocentric representations of the scene thatwere not updated when they moved, and thus showedviewpoint-dependent response patterns. In fact, Mouet al. (2004) also argued that observers in their studymight have been forced to use allocentric rather thanegocentric representations because the observers weredelayed approximately 10 s from pointing to a targetafter moving within the scene. Furthermore, studiesthat have found evidence of observer movement lead-ing to spatially updated representations have not hadsuch delays (e.g., Avraamides, 2003; Farrell & Robert-son, 1998; Reiser, 1989). Thus, the goal of our presentwork was to systematically examine the eVects ofdelaying observer movement, after encoding a scene,on the observers’ scene recognition RT and accuracyproWles over a range of angles, and we compared theseeVects to the eVects of delaying observers from viewingequivalent rotated versions of the same scenes.

Experiment 1

Prior to systematically examining the eVects of delay-ing locomotion, we re-examined the eVect of observermovement, over a range of angles around a scene, onscene recognition RT and accuracy. We also comparedthe eVects of observer movement to the eVects ofequivalent viewpoint changes produced by scenemovement. Similar to our previous work (Motes et al.,in press), observers learned a spatial layout of objectsfrom a single perspective, and after learning the layout,observers made scene recognition judgments on subse-quently viewed scenes. The views of the judged scenewere varied by having observers either walk to viewingstations (0°–360°) placed around the scene or by hav-ing observers remain at the encoding station and rotat-ing the scenes (0°–360°) from the encoding orientation.

In our previous experiment (Motes et al., in press),observers exited and re-entered the room betweentrials so that they would not hear adjustments being madeto the scene. However, Wang and Spelke (2000) haveshown that self-rotation (compared to not rotating) fora short period after learning a scene negatively aVectsself-to-object pointing judgments, that is, impairs ego-centric representations. Although we had observersbegin each trial at the encoding station in order to facil-itate re-orientation, the use of the encoding station as are-orientation landmark might not have been eVectiveif exiting and re-entering was akin to self-rotation inthat it impaired the observers’ egocentric representa-tions. To rule out this plausible alternative explanation,in the current study we changed our previous method-ology so that observers remained in the testing roomthroughout the duration of the experiment.

Method

Participants

Fifty-one students from Rutgers University partici-pated in the experiment in exchange for course creditor monetary compensation. Twenty-six were randomlyassigned to the scene movement condition, and 25were randomly assigned to the observer movementcondition.

Stimuli and apparatus

The experiment was conducted in a darkened room. ADell 17� LCD Xat-panel monitor was laid horizontallyon a circular table (radius = 54 cm). A black clothcovered the monitor and table, except for a circle(radius = 11 cm) that was cut out of the black cloth thatwas centered over the viewing screen of the monitor,within which all of the scenes were shown. The blackcloth prevented the outer edges of the monitor and theinner edges of the viewing screen from being used asframes of reference when learning and judging thescenes.

Viewing stations were created with ten occludingscreens (44.6 £ 180 cm) that surrounded the monitorand table. Each screen had a horizontally centeredviewing window (5.8 £ 12 cm) cut into the screen140 cm from the Xoor and 59 cm from the top of theviewing screen of the monitor. The windows were36° apart. From the center of a viewing window, thevisual angle of the display was approximately 12°. Toeliminate the potential use of the ceiling and the wallsof the room as frames of reference, the ceiling of theroom was covered with black cloth, and black cloth,


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hanging from the ceiling to the Xoor, encircled theoccluding screens and an approximately 58 cm widepath through which the experimenter and observerscould walk.

On one of the screens, a Start sign was placed abovethe viewing window. For both the scene rotation andobserver movement groups, this was the station fromwhich the scene that was to-be-remembered through-out the duration of the experiment was encoded. In thescene rotation condition, observers remained at thisstation throughout the study, whereas in the observermovement condition, observers began each trial at thisstation, and on trials in which they judged the scenesafter moving, they moved counterclockwise from thisstation. The encoded scene consisted of a computer-ized display of ten objects (see Fig. 1), and to testwhether observers had indeed learned the scene, theobservers recreated the scene with cutouts of theobjects on a magnetic clipboard.

Sixty-six scenes were judged by the observers.Thirty-three variations of the 10-object encoded scenewere created. For these scenes the locations of two ran-domly selected objects were switched with each other(e.g., see Fig. 1). Each of these 33 scenes and each ofthe 33 copies of the encoded scene were then randomlyassigned to 1 of 11 viewing angles (0°–360°). That is,for the scene rotation condition, 27 diVerent and 27

same scenes were rotated, clockwise between 36° and324° from the encoded scene orientation. The other 12scenes (6 same and 6 diVerent) were kept at theencoded scene orientation and served as 0° (3 same and3 diVerent) observer and scene movement scenes and360° (3 same and 3 diVerent) observer and scene move-ment scenes. For the observer movement condition, all66 scenes were kept at the same orientation as theencoded scene. The same scenes were used for theequivalent scene movement and observer movementviewing angles.

For the scene recognition task, observers in bothconditions used a handheld, wireless, radio-frequency,computer mouse to indicate whether the scenes werethe same as the encoded scene (right mousebutton = same and left = diVerent). An E-Prime (Psy-chological Software Tools, Version 1.1) program pre-sented the scenes and recorded RT and accuracy.When recording RT, the program started a softwareclock when the judged scene was shown and stoppedthe software clock when one of the mouse buttons waspressed. Pressing the same button triggered the pro-gram to play a digital audio Wle saying “same”. Pressingthe diVerent mouse button triggered the program toplay a digital audio Wle saying “diVerent; which objectswere switched?” The experimenter recorded theobservers’ verbal responses on a trial record sheet, and

Fig. 1 Diagram of scene recognition trials for Experiment 1. Thediagram depicts two viewpoint-equivalent trials (Trial n and Trialn + 1) for the observer and scene movement groups. On each tri-al, observers initially waited at the encoding station (start) for 3 s.Observers in the scene movement group remained at the encod-ing station throughout the experiment and judged scenes thatwere rotated (0°–324° in 36° increments) from the encoded scene

orientation. Observers in the observer movement group walked(0°–360° in 36° increments) to a new viewing station on each trialand made scene recognition judgments. Trial n depicts observerand scene movement viewpoint-equivalent, 72°, diVerent trials,and Trial n + 1 depicts subsequent observer and scene movementviewpoint-equivalent, 0°, same trials


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the experimenter used a small Xashlight to see whenrecording responses, for the observers to see andarrange the cutouts, and to maneuver around the path.

Procedure

Both the scene and observer movement groups weretold that they would Wrst have to learn the spatialarrangement of a scene composed of geometricobjects. After entering the testing room but beforelearning the encoded scene, the observers were disori-ented to reduce the possibility of their using the dooror other stimuli external to the testing room as spatialreference points. The observers closed their eyes andwere led counterclockwise by the experimenter par-tially around the occluding screens, then rotated inplace three times, led clockwise partially back, rotatedthree times, led counterclockwise partially aroundagain, rotated three times, and then opened their eyesand attempted to point to the door. However, noneaccurately pointed to the door.

Observers were then led by the experimenter to theencoding station where they learned the layout of thescene that they were to remember for the duration ofthe study. Observers were shown the scene for 1 min.They counted “1-2-3” aloud to interfere with their useof verbal coding strategies. After 1 min, the scenedisappeared, and the observers were asked to recreatethe scene. They repeated this procedure until theyaccurately reproduced the scene.

After learning the scene, the observers were toldthat they would then be shown scenes that either wouldbe the same as the encoded scene or diVerent from theencoded scene in that the locations of two of theobjects in the scene would be switched (this was dem-onstrated with the cutouts). Observers in the scenemovement group were then told that the judged scenesmight be rotated from the orientation of the encodedscene (this was also demonstrated with the cutouts) butthat they were to judge the scene as diVerent only if thelocations of two objects were switched, regardless ofwhether the entire scene was rotated or not. Observersin the observer movement condition were told that theorientation of the scene would remain the samethroughout the duration of the experiment.

Observers completed Wve practice trials randomlyselected from the 66-scene/angle combinations and thencompleted the 66 scene recognition trials. Each observerworked through the trials in one of two Wxed randomorders, and the observers were instructed to respondboth quickly and accurately. Testing lasted 1–1.5 h.

At the beginning of each trial, observers in theobserver movement group waited at the encoding

station for 3 s (see Fig. 1). A tone then played cueingthe experimenter to escort the observer to the scenejudgment station listed on the experimenter’s trialrecord sheet. After reaching the judgment station, theobserver pressed the left mouse button to view thejudged scene and then entered a scene recognitionjudgment. The observer returned to the encoding sta-tion, and pressed the mouse button to begin the nexttrial.

Observers in the scene movement group remainedat the encoding station throughout the duration of theexperiment (see Fig. 1). They also waited through a 3 sdelay between each trial. After 3 s, a tone played, andthe experimenter directed the observer to press the leftmouse button to view the scene. The observer thenentered the scene recognition judgment.

Results

Scene recognition accuracy

For accuracy, responses with RTs below 750 ms(0.09%, 3 of 3,366, of the total trials) were deleted;these were trials in which the observers inadvertentlypressed the response button before actually viewingthe judged scenes. For the remaining data, the propor-tion of correct responses for each viewing angle wasthen calculated for each observer, and a mixed-modelANOVA (2 Movement Group X 11 Angular Distance)was calculated using these accuracy data. Mean accu-racy as a function of movement group and angulardistance is shown in Fig. 2a.

ANOVA revealed a signiWcant eVect of angular dis-tance, F(10, 490) = 3.71, p < 0.01, but neither the maineVect of movement group nor the interaction weresigniWcant, F(1, 49) < 1 and F(10, 490) < 1, respectively.However, upon examining the means per group andangle, we found that the means were signiWcantly lowerin the 0° condition than in the equivalent 360° for boththe scene and observer movement groups, t(25) = 3.08,p < 0.01, and t(24) = 3.07, p < 0.01, respectively. Uponfurther investigation, we discovered below chanceperformance for only one of the 0° condition diVerentscenes (6 of 13 observers in the observer movementgroup and 6 of 13 observers in the scene movementgroup answered correctly), a scene in which the octa-gon and hexagon were switched. This scene was alsoused on the other stimulus list, but the scene wasviewed 216° from the encoded orientation. At the 216°viewing angle, scene recognition performance was alsobelow chance (4 of 12 observers in the observer move-ment group and 4 of 13 observers in the scene move-ment group answered correctly). No other scenes


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showed similar below chance performance patterns.Together, these data suggested that the mean for the 0°condition and for the 216° condition were artiWciallylow due to the inclusion of these diYcult to discrimi-nate trial types. Thus, we removed these trials andreanalyzed the accuracy data. Mean accuracy as a func-tion of movement group and angular distance is shownin Fig. 2b.

After removing the trials in which the octagon andhexagon were switched, neither the main eVect ofangular distance, the main eVect of movement group,nor the interaction were signiWcant, F(10, 490) = 1.59,p > 0.1, F(1, 49) < 1, and F(10, 490) < 1, respectively.Thus, consistent with the results from our previousexperiment (Motes et al., in press), accuracy did notsigniWcantly diVer with angular distance for either thescene or observer movement groups.

Scene recognition RT

Scene recognition RTs for each observer werescreened for outliers. First, RTs below 750 ms (0.09%,3 of 3,366, of the total trials) and above 30 s (1.16%, 39of 3,366, of the total trials) were deleted. Then,RTs § 2.5 SDs from an individual observer’s mean RTwere deleted (observer movement = 2.14%, 35 of1,632, and scene movement = 2.42%, 41 of 1,692).After deleting outlier RTs, mean RTs for correctresponses for each viewing angle were calculated foreach observer, and a mixed-model ANOVA (2 Move-ment Group X 11 Angular Distance) was calculatedusing these data. Mean RT as a function of movementgroup and angular distance is shown in Fig. 2c.

ANOVA revealed the main eVect of angular dis-tance was signiWcant, F(10, 490) = 5.77, p < 0.01, but

Fig. 2 Scene recognition accuracy and response time as a func-tion of movement group and angular distance. The open circlesshow the data for observers in the observer movement group, andthe Wlled circles show the data for observers in the scene move-

ment group. a Shows scene recognition accuracy for all trials, bshows scene recognition accuracy after deleting trials in which theoctagon and hexagon were switched, and c shows scene recogni-tion response time

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neither the main eVect of movement group nor theinteraction were signiWcant, F(1, 49) < 1 and F(10,490) < 1, respectively. Trend analyses of the eVect ofangular distance revealed that the quadratic compo-nent was signiWcant, F(1, 49) = 29.90, p < 0.01. To fur-ther examine this quadratic trend, the linearcomponents from 0° to 180° and from 180° to 360°were analyzed. The linear trend components weresigniWcant for both the eVect of angular distance from0° to 180°, F(1, 49) = 10.31, p < 0.01, and from 180°to 360°, F(1, 49) = 10.37, p < 0.01, indicating that theincrease in RT for both groups was greater with largerangular distances.

Thus, consistent with our previous Wndings (Moteset al., in press), regardless of whether the scene wasmoved or the observer moved, the analyses showedthat RT increased with angular distance from theencoded view. Furthermore, although the movementgroup by angular distance interaction was not signiW-cant, we explicitly examined RT diVerences betweenthe scene and observer movement groups at each angu-lar distance, but none of the diVerences were signiW-cant, all ps > 0.05. Given the increase in RT withangular distance for both groups and the failure to WnddiVerences between the groups for any of the angulardistances, the data suggest that both groups formedviewpoint-dependent representations of the encodedscene and possibly performed mental rotation transfor-mations to compare their viewpoint-dependent repre-sentations of the encoded scene to the judged sceneswhen the angular distances varied.

Experiment 2

In Experiment 2, we systematically investigated theeVect of delays following scene encoding and observermovement. As in Experiment 1, observers wereassigned to either an observer or scene movementgroup. DiVerent from Experiment 1, however, observ-ers viewed a diVerent 4-object scene on each trial.Then, following a 0, 6, or 12 s delay, observers viewedthe scene from either the same or a diVerent perspec-tive (i.e., observers in the observer movement groupwalked around the scene or observers in the scenemovement group viewed rotated scenes) and judgedwhich object in the scene had been moved. To examinethe eVects of delays above and below 10 s, we used ashort-term retention procedure rather than the long-term retention procedure used in Experiment 1. Thescene set-size was also reduced to four objects, from 10used in Experiment 1, to be consistent with the con-straints of visual working memory (Luck & Vogel,

1997). The procedure and set-size were consistent withthose used in studies that previously reported Wndinglocomotion-induced spatial updating eVects on scenerecognition (Simons & Wang, 1998; Wang & Simons,1999).

Method

Participants

Thirty students from Rutgers University participatedfor course credit. Fifteen participants were randomlyassigned to the scene movement condition and Wfteenparticipants were randomly assigned to the observermovement condition.

Stimuli and apparatus

The arrangement of the testing room and apparatuswere identical to Experiment 1, with the exception ofthe stimuli. Thirty-six diVerent 4-object, computerized,encoded scenes were designed. For each scene, fourobjects were randomly selected from a set of 12, easilyidentiWable objects (snowXake, pound sign, square,Xower, wheel, cross, star, triangle, octagon, sun, circleand donut, see Fig. 3a, each measuring from 2.5 to3.5 cm in height and 2.2 m to 3.5 cm in width). Eachobject was then placed in one randomly selected loca-tion of 21 predeWned locations (see Fig. 3b). For eachencoded scene, a judged scene was created by ran-domly selecting one object from the encoded scene andmoving that object to one of the randomly selected 17unoccupied spaces. Each of the 36 pairs of encodedand judged scenes were then randomly assigned to oneof six viewing angles (0°–180° in 36° increments). Forthe scene movement condition, 30 scene pairs wererotated clockwise to one of the Wve rotated viewingangles. The remaining six pairs served as 0° scene andobserver movement scenes.

Three randomly arranged lists of the 36 trial pairswere then created. Observers in both groups workedthrough three blocks of 36 trials (i.e., each list), oneblock for each delay condition. Trial lists and delayconditions were counterbalanced using a 3 £ 3 LatinSquare design. Testing lasted approximately 1 h.

Procedure

Observers in the scene movement group were told thatthe judged scenes might be rotated from the orienta-tion of the encoded scenes but that they were to iden-tify the single object moved within the scene, and oneach trial, they were told the magnitude and direction


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of the scene rotation. Observers in the observer move-ment group were told that the orientation of the scenewould remain the same regardless of whether theymoved from the encoding station or not. Observerswere then taken into the testing room, put through thedisorientation procedure used in Experiment 1, andthen led to the Wrst encoding station.

On each trial, observers viewed a 4-object scene for3 s. Then, the screen went blank for a delay period of0, 6, or 12 s, depending on the trial block. After which,a tone played to indicate that the delay period hadpassed. Observers in the scene movement group thenpressed the right mouse button to view the judgedscene. Observers in the observer movement groupwere led by the experimenter to the judgment stationand instructed to press the right mouse button to viewthe judged scene. Observers in both groups pressed theright mouse button to indicate when they recognizedwhich object had been moved, and they verballyreported the object to the experimenter. Observerswere told whether there would be a delay before begin-ning each block, but they were not told the duration ofthe delay. Observers completed four practice trials atthe beginning of each block.

Observers in the observer movement group did notreturn to the original encoding station after judging thescene but instead moved one viewing station to the left

of the judgment station to encode the next scene. Thischange was made to reduce the total testing time.Observers in the scene movement group also did notremain at the original encoding station throughout theexperiment. They, instead, changed viewing stationsbetween trials to encode the scenes from the same sta-tions as observers in the observer movement group,thus working through viewpoint-equivalent sets of tri-als (see Fig. 3c).

Results

Scene recognition accuracy

For accuracy, responses with RTs below 750 ms(0.22%, 7 of 3,240, of the total trials) were deleted;these were trials in which the observers inadvertentlypressed the response button before actually viewingthe judged scenes. For the remaining data, the propor-tion of correct responses for each viewing angle wasthen calculated for each observer, and a mixed-modelANOVA (2 Movement Group X 3 Delay X 6 AngularDistance) was calculated using these accuracy data.Mean accuracy as a function of movement group bydelay by angular distance is shown in Fig. 4a, b.

ANOVA revealed a signiWcant eVect of angulardistance, F(5, 140) = 20.77, p < 0.01, and a signiWcant

Fig. 3 Diagram of stimuli and observer movement trials forExperiment 2. a Shows the 12 objects used to create the 4-objectscenes, and b shows the template used to deWne the object loca-tions. c Depicts two trials for the observer movement group. Oneach trial, an observer had 3 s to encode a scene that was followedby a delay period of 0, 6, or 12 s. Then, the observer walked (0°–180° in 36° increments) to a new viewing station and made a scene

recognition judgment. At the conclusion of each trial, the observ-er walked one viewing station to the left to begin the next trial.Observers in the scene movement group also changed viewingstations between trials to encode the scenes from the same sta-tions as observers in the observer movement group, thus workingthrough viewpoint-equivalent sets of trials


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angular distance by delay interaction, F(10, 280) = 2.09,p < 0.05, but the main eVects of delay, F(2, 27) < 1, andmovement group, F(1, 28) = 1.94, p > 0.05, and theangular distance by movement group, F(5, 140) = 1.30,p > 0.05, delay by movement group, F(2, 27) < 1, andangular distance by delay by movement group, F(10,280) < 1, interactions were not signiWcant. Trend analy-ses of the eVect of angular distance revealed thatthe linear trend component was signiWcant, F(1,28) = 98.30, p < 0.01. Thus, unlike our previous Wndings(Experiment 1 above and Motes et al., in press),regardless of whether the scene was moved or theobserver moved, accuracy decreased with increasingangular distance from the encoded view. Thus, the typeof retention paradigm, short-term versus long-term,appeared to aVect the representation available formaking the scene recognition judgments. This diVer-ence across studies, however, must be treated with

caution because the judgment tasks also diVered.Finally, the Wnding that the impairment eVects ofobserver movement on scene recognition increasedwith angular distance suggests that previously reportedmixed Wndings (Simons & Wang, 1998; Wang &Simons, 1999) might have been due to the relativelyshort angular distances used (i.e., impairment eVects at47° should be weaker than impairment eVects at largerangular distances).

Follow-up analyses of the angular distance by delayinteraction revealed that the eVects of angular distancefor the three delay conditions were signiWcant, 0 s F(5,145) = 7.63, p < 0.001, 6 s F(5, 145) = 11.80, p < 0.001,and 12 s F(5, 145) = 9.51, p < 0.001. The linear trendcomponents for all three delay conditions were signiW-cant, 0 s F(1, 29) = 31.27, p < 0.001, 6 s F(1, 29) = 53.99,p < 0.001, and 12 s F(1, 29) = 32.59, p < 0.001. Thus,regardless of the length of the delay and whether the

Fig. 4 Scene recognition accuracy and response time as a func-tion of movement group, delay, and angular distance. a, b Showthe accuracy for the scene and observer movement groups,respectively, and c, d show the RT for the scene and observer

movement groups, respectively. Open squares represent the 0 sdelay condition, open circles represent the 6 s delay condition,and Wlled circles represent the 12 s delay condition

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observer or scene moved, accuracy decreased withangular distance. Therefore, the analyses of the accu-racy data did not reveal that delays aVected the observ-ers’ representations. Further analyses of the angulardistance by delay interaction revealed a signiWcantdiVerence only at 108°, F(2, 58) = 4.40, p < 0.05. At108°, observers in both groups were less accurate in the0 s delay condition (M = 0.50) than in either the 6 s(M = 0.59) or 12 s (M = 0.63) conditions, t(29) = 2.09,p < 0.05, and t(29) = 3.29, p < 0.01, respectively. ThisWnding, however, was not a part of a systematic pat-tern, making the interpretation of this result unclear.

Scene recognition RT

Scene recognition RTs for both groups were screenedfor outliers. RTs below 750 ms (0.22%, 7 of 3,240, ofthe total trials) and above 30 s (0.09%, 3 of 3,240, ofthe total trials) were deleted. RTs § 2.5 SDs from anindividual observer’s mean RT were deleted (observermovement = 2.23%, 36 of 1,615, and scene movement= 2.6%, 42 of 1,615). After deleting outlier RTs, meanRTs for correct responses for each viewing angle anddelay period were calculated for each observer and amixed-model ANOVA (2 Movement Group X 3 DelayX 6 Angular Distance) was calculated. Four observerswere excluded from further analyses, two from eachgroup, due to incomplete data sets (i.e., incorrectlyresponding to all six trials for at least one of the delayby angular distance conditions). Mean RT as a functionof movement group by delay by angular distance isshown in Fig. 4c, d.

ANOVA revealed a signiWcant eVect of angulardistance, F(5, 120) = 5.79, p < 0.001, and a marginallysigniWcant angular distance and movement groupinteraction, F(5, 120) = 1.91, p = 0.10, but the maineVects of delay, F(2, 48) < 1, and movement group, F(1,24) < 1, and the angular distance by delay, F(10,240) < 1, the delay by movement group, F(2, 48) = 1.07,p > 0.10, and angular distance by delay by movementgroup, F(10, 240) < 1, interactions were not signiWcant.Trend analyses of the eVect of angular distancerevealed that the linear component was signiWcant, F(1,24) = 19.75, p < 0.001. However, follow-up tests of themarginally signiWcant angle by movement group inter-action revealed that the eVect of angular distance wassigniWcant for the observer movement group, F(5, 60) =9.32, p < 0.001, but not the scene movement group,F(5, 60) < 1. Trend analyses for the observer move-ment group revealed that the linear trend componentwas signiWcant, F(1, 12) = 31.17, p < 0.001 (for the scenemovement group, F(1, 12) = 2.02, p = 0.18). Thus, con-sistent with our previous Wndings (Experiment 1 and

Motes et al., in press), when the observers movedaround the scenes, RT increased with angular distancefrom the encoded view.

Importantly, the length of delay between sceneencoding and observer movement did not have adetectable eVect on scene recognition accuracy or RT.Thus, the data do not support our hypothesis that ourprevious failure to Wnd evidence of locomotion-induced spatial updating was due to delays betweenscene encoding and locomotion (Motes et al., in press).In the present study, we did not Wnd evidence of fullspatial updating even when there was not a delay. InExperiment 2, the retention interval diVered withwhether the observer moved or the scene was moved.

Observers in both groups waited 0, 6, or 12 s afterencoding the scene, but observers in the observermovement group had to maintain their representationsof the scenes for the duration of the locomotion period,thus adding additional time to the retention interval forthis group. However, if maintenance duration alonewere relevant, this additional time should have led toeven greater diVerences between the 0 s condition andthe 6 and 12 s conditions for the observer movementgroup, but in fact, no signiWcant diVerences weredetected for any of the angular distances. With respectto the eVects of locomotion delays on automatic spatialupdating in general, future research will have to exam-ine whether delays aVect automatic spatial updating inother research paradigms (e.g., tasks like those used byFarrell & Robertson, 1998; Farrell & Thompson, 1998;Rieser, 1989).

Additionally, the data from Experiment 2 show thatour previous failures to Wnd evidence of locomotionleading to spatially updated representations of sceneswere not due to our use of 10 or 11-object scenes(Experiment 1 and Motes et al., in press, respectively).Although we only used 4-object scenes in Experiment2, we still did not Wnd evidence of full spatial updating.Furthermore, in other research (Motes, Finlay, &Kozhevnikov, 2006), we have systematically examinedthe eVect of varying scene set-size using 4-, 5-, 6-, 8-,and 10-object scenes, and although the eVects of angu-lar distance varied with set-size, none of the set-sizesyielded clear full spatial updating eVects. The datafrom Experiment 2 also suggest that our previous fail-ures were not due to our methods of having observersreproduce the scenes to show that they had learnedthem. In Experiment 2, the costs associated with loco-motion were similar to our previous Wndings, butobservers did not reproduce the scenes.

Finally, although we found evidence of systematicscene recognition costs associated with observer move-ment while Simons and Wang (1998, Experiment 1) did


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not, there were diVerences between the materials usedin these studies, and such diVerences might explain thecontrasting results. For example, we used computer-ized displays of relatively simple, easily identiWable,geometric Wgures, and our display space was relativelysmall (radius = 11 cm; covering an approximate 12°visual angle), whereas Simons and Wang used three-dimensional, real objects, and their display space waslarger (radius = 61 cm). However, in Motes et al. (inpress), we used three-dimensional, real geometricobjects placed across a circular table similar in size(radius = 54 cm) to the table used by Simons and Wang(1998), yet we found locomotion induced costs similarto those reported in the present Experiments 1 and 2.Furthermore, Simons and Wang (1998, Experiment 2;Wang & Simons, 1999, Experiment 1) also found costsassociated with observer movement in two of theirstudies (i.e., change detection accuracy was lower whenobservers moved but the scene remained stationarythan when both the observer and the scene remainedstationary). Thus, it does not appear that diVerences inthe properties of the displays, per se, account for thecosts. Other diVerences, like the range and number ofangular distances used or diVerences in the availabilityof the walls of the room as a frame of reference, mightbe relevant. For example, the walls were visually avail-able in Simons and Wang’s (1998, Experiment 1) studywhere they did not Wnd that observer movement led toscene recognition costs, but the walls were neither visu-ally available in our studies nor in Simons and Wang’sstudies where observer movement costs occurred.

Discussion

Across Experiments 1 and 2, we investigated whetherprocesses associated with locomotion would automati-cally update an observer’s representation of a scene tobe spatially consistent with the observer’s perspectiveof the scene after moving (e.g., Farrell & Robertson,1998; Reiser, 1989). In Experiment 2, we systematicallyinvestigated whether delays between encoding a sceneand moving around that scene would aVect whether theobserver movement would produce spatially updatedrepresentations of the scene. Across the two experi-ments, we failed to Wnd that locomotion about a sceneclearly produced spatially updated representations ofthe scene.

Thus, the data from the two studies question thegenerality of locomotion producing updated spatialrepresentations. Based on a dynamic model of spatialupdating oVered by Mou et al. (2004), we argued, fol-lowing Experiment 1, that our observers’ egocentric

representations of the scene, formed when the observ-ers learned the scene, might have faded over theduration of the scene recognition portion of the experi-ment, possibly forcing the observers to use moreenduring, allocentric representations of the scene thatwere not updated when they moved. However, inExperiment 2, we did not Wnd evidence to support thishypothesis.

One of the possible explanations for our resultsis that observer movement might lead to spatiallyupdated representations in the case of externallyviewed scenes only when the orientation change is lim-ited to short angular distances around the scene (i.e., atleast, not beyond 72° based on Experiment 2) or withinthe scene (i.e., at least not beyond 90° based on Mouet al., 2004). Viewing a scene externally might result inan observer processing a psychological separation ofoneself from the other objects in the environment. Wesuspect that such a psychological separation occurswhen a physical boundary (e.g., partially occludingpanels) is imposed between the observer and the scene,but we are not suggesting that psychological separationoccurs only in the presence of physical boundaries.Internally viewed scenes, on the other hand, might leadto spatially updated representations of scenes over alarger range of orientation changes (e.g., at least 360°,Rieser, 1989, barring other forms of interference likespinning quickly enough to make oneself dizzy). Inter-nally viewed scenes are those in which an observerdoes not perceive a psychological boundary betweenoneself and other objects in the scene (e.g., when one issurrounded by objects in the scene [Farrell & Robin-son, 1998; Rieser, 1989] or when a layout of objectsencompasses a large expanse of the observer’s visualWeld [Farrell & Thompson, 1998]). Internally viewedscenes might then elicit stronger egocentric coding ofthe spatial relations of objects in a scene or sensori-motor representations (Avraamides, 2003). Thus, inExperiments 1 and 2 and our previous work (Moteset al., in press), the scenes were externally viewed dueto the occluding screens. Therefore, the representa-tions of the scenes were not updated as observersmoved around the scenes, regardless of whether loco-motion after encoding the scenes was delayed or not.

In conclusion, the present experiments revealed thatscene recognition following observer movement aroundscenes does not necessarily lead to automatic spatiallyupdated representations of those scenes and add to theexisting conditions in which automatic spatial updatinghas not been found. The present experiments showedthat our previous failure to Wnd evidence of spatialupdating (Motes et al., in press) was not due to disori-entation caused by our previous procedure and that


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delays between encoding a scene and movement aboutthat scene do not aVect spatial updating. Furthermore,the present experiments raise important questions con-cerning the inXuence of encoding points of view and theeVects of locomotion on spatial updating.

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