This article was downloaded by: [University of Tokyo]On: 14 February 2012, At: 19:44Publisher: Psychology PressInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK

Visual CognitionPublication details, including instructions for authorsand subscription information:http://www.tandfonline.com/loi/pvis20

Sustained attention can createan (illusory) experience ofseeing dynamic changeRyoichi Nakashima a & Kazuhiko Yokosawa aa Department of Psychology, The University of Tokyo,Tokyo, Japan

Available online: 14 Feb 2012

To cite this article: Ryoichi Nakashima & Kazuhiko Yokosawa (2012): Sustained attentioncan create an (illusory) experience of seeing dynamic change, Visual Cognition,DOI:10.1080/13506285.2012.658102

To link to this article: http://dx.doi.org/10.1080/13506285.2012.658102

PLEASE SCROLL DOWN FOR ARTICLE

Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions

This article may be used for research, teaching, and private study purposes.Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expresslyforbidden.

The publisher does not give any warranty express or implied or make anyrepresentation that the contents will be complete or accurate or up todate. The accuracy of any instructions, formulae, and drug doses should beindependently verified with primary sources. The publisher shall not be liablefor any loss, actions, claims, proceedings, demand, or costs or damages

whatsoever or howsoever caused arising directly or indirectly in connectionwith or arising out of the use of this material.

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

Sustained attention can create an (illusory) experience

of seeing dynamic change

Ryoichi Nakashima and Kazuhiko Yokosawa

Department of Psychology, The University of Tokyo, Tokyo, Japan

Recent studies speculated that two types of change detection exist, one involvingthe experience of seeing dynamic change (change over brief interval), the otherinvolving detecting a completed change (change over long interval), with only theformer requiring sustained attention. To examine this supposition, a flicker changedetection task was conducted in which the spatial location of objects was manipu-lated (shift, no-shift). In shift conditions, changed image display appeared indifferent locations than they did in the original display. The time interval separatingimages was manipulated (200 or 1000 ms). Results showed that a shift led to poorchange detection only in the short interval condition. The performance decline bythe image shift was not attenuated even when participants knew beforehandwhether or not a shift would occur. Results indicate that sustained attention, whichis sustained for a brief time, is related to the experience of seeing dynamic change.

Keywords: Change blindness; Dynamic change detection; Flicker change

detection task; Spatial attention; Sustained attention.

When we view a scene, we typically experience that it provides a rich, per-

haps complete, representation of the scene. However, it is also known that we

cannot detect relatively large changes during saccades between two successive

images (e.g., Grimes, 1996), during an eye blink (O’Regan, Deubel, Clark, &

Rensink, 2000), with ‘‘mudsplashes’’ (O’Regan, Rensink, & Clark, 1999), or

with images separated by brief blanks (e.g., Rensink, O’Regan, & Clark,

1997). This inability in change detection is called ‘‘change blindness’’.

Please address all correspondence to Kazuhiko Yokosawa, Department of Psychology,

Graduate School of Humanities and Society, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku,

Tokyo, 113-0033, Japan. E-mail: yokosawa@l.u-tokyo.ac.jp

This study was supported by a grant from the Research Fellowship of the Japan Society

for the Promotion of Science for Young Scientists to RN, and by a Grant-in-Aid for Scientific

Research from the Japan Society for the Promotion of Science awarded to KY.

R. N. is currently at Tohoku University as a postdoctoral researcher.

VISUAL COGNITION, 2012, iFirst, 1�19

# 2012 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business

http://www.psypress.com/viscog http://dx.doi.org/10.1080/13506285.2012.658102

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

Why, then, does change blindness occur? Some previous studies investi-

gating change blindness have suggested that we can detect a local visual

change mainly when attention is sustained from prechange visual informa-

tion presented through the postchange visual information (Rensink, 2000a,

2000b, 2002; Rensink et al., 1997). Such findings have also been interpretedto mean that sustained attention plays a critical role of detecting local object

changes.

On the other hand, recent studies have revealed that change blindness may

be attributed to various factors, such as failures of encoding, retrieval, and

comparison (Hollingworth, 2003, 2006; Hollingworth & Henderson, 2002;

Hollingworth, Williams, & Henderson, 2001; Mitroff, Simons, & Levin,

2004). For example, Hollingworth and Henderson (2002) demonstrated that

although attention was not sustained from a pre- through postchange object,change was detected when attention focused upon the prechange object and

then upon the postchange object. Thus, these studies suggest that sustained

attention is not essential to the detection of changes.

Now, many studies suggest that people can detect a visual change in

a scene without sustained attention (see Hollingworth, 2006, 2008). This

raises the question: ‘‘What role is played by sustained attention in change

detection?’’ Rensink (Rensink, 2002; Simons & Rensink, 2005) proposed

that, whereas sustained attention may not be necessary in detecting thata change has occurred, attention is necessary for the experience of seeing dy-

namic change. This proposal hypothesizes a phenomenal distinction between

two types of change detection; one concerns the experience of seeing a

dynamic change as it occurs and other involves detection of a change after it

has been completed. The former refers to the perception of the transforma-

tion, that is, a change is perceived as a dynamic visual event. This experience

arises in situations where an original and changed scene images are sepa-

rated by a short interstimulus interval (ISI). By contrast, the latter refersan observer’s ability to detect a difference without the experience of seeing

the change happen in real time. This tends to occur when images of an

original and a changed scene are either separated by a long ISI or across a

saccade.

Support for this distinction comes from an experiment by Hollingworth

(2008) in which participants evaluated their impression of ‘‘seeing the change

occur’’. In Hollingworth’s experiment, the original and changed scene images

(250 ms each) were presented in a flicker paradigm, with an ISI of either200 ms, 1 s, or 5 s. Participants were to attend to changes of a particular target

object (identified initially). They reported having a strong impression of

‘‘seeing the change occur’’ at the 200 ms ISI, a weak impression at the 1 s ISI,

and no impression of experiencing change with the 5 s ISI. These results

confirm that the experience of seeing dynamic change is more likely when

two images are presented with a short ISI. Nevertheless, these results cannot

2 NAKASHIMA AND YOKOSAWA

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

explain whether sustained attention plays a decisive role that is specific to

the experience of dynamic change detection, because Hollingworth did not

confirm whether attention was sustained through the blank duration in the

experiment.

Several previous studies (e.g., Ariga, Kawahara, & Watanabe, 2011;Duncan, Ward, & Shapiro, 1994; Posner & Cohen, 1984; Raymond, Shapiro,

& Arnell, 1992; Theeuwes, Godijn, & Pratt, 2004) have suggested that atten-

tion can be sustained for a brief time. For example, in the rapid serial visual

presentation (RSVP), in which a sequence of visual stimuli containing two

target stimuli is presented and all stimuli appear at the same spatial location,

observers often fail to detect the second (salient) target if it occurs between

200�500 ms after the first target (Raymond et al., 1992). This is called

the attentional blink (AB). An AB indicates that if attention is focused on oneearlier stimulus (e.g., the first target), then it will continue to be focused on

this item. Indeed, the claim is that it cannot be focused on subsequent stimuli

at all for a shorter afterperiod. Furthermore, a recent study using RSVP

task revealed an attentional awakening (AA); this refers to the possibility

that attentional focusing process is not fully established early in an RSVP

sequence and thus precludes complete processing of the target. Instead,

attention becomes active gradually (Ariga & Yokosawa, 2008). Ariga et al.

(2011) reported that an enhanced state of attention was reset after an unfilledgap of 500�1000 ms that was inserted in the RSVP sequence, based on the

results that AA occurred in the second RSVP sequence after a long blank

duration. This result indicated that the attentional state cannot be maintained

for a long period of time (e.g., 1000 ms blank duration).

Another example of the sustainment of attention is illustrated in the

studies of inhibition of return (IOR; Posner & Cohen, 1984). IOR involves a

mechanism that encourages orienting towards new locations. It is experi-

mentally demonstrated in situations in which an initial response to aperipheral visual event results in facilitation of the processing of nearby

stimuli, owing to a reflexive shift of attention towards the neighbouring

source of stimulation. However, when the peripheral event is not task relevant

and attention has had time to disengage from it, an inhibitory aftereffect can

be measured in the delayed response to stimuli subsequently displayed at the

originally cued location. This inhibitory aftereffect appears about 300 ms

after the presentation of the initial visual event. In other words, IOR also

indicates that attention can be sustained only for a short time.Moreover, the studies that directly measured attentional dwell time in

human vision (e.g., Duncan et al., 1994; Theeuwes et al., 2004) reported that

a dwell time of attention was around a few hundred milliseconds. Although

the studies described earlier indicated that focused attention can be sus-

tained for a short time, they cannot reveal the relationship between sustained

attention and change detection.

SUSTAINED ATTENTION AND CHANGE DETECTION 3

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

In the present study, we examine an unresolved issue surrounding the

relationship between sustained attention and change detection. To address

this issue, we consider whether or not attention can be sustained only

for only a brief blank time interval and during this brief interval observers

can experience seeing dynamic change. With regard to attention, we define

sustained attention as ‘‘endogenous spatial attention that maintains its state

for a period of time’’;1 it is operationalized as an intentional focus upon

a local area within a larger visual scene. This assumption is based on two

established facts. First, change detection is, to some degree, an active process,

i.e., without an active attentional focus change blindness is usually observed.

Second, change detection across a saccade (correlated with a movement of

attention) reflects the ‘‘detection of completed change’’ (Hollingworth,

2008); this indicates that spatially focused and staying attention can enable

the dynamic change detection.

EXPERIMENT 1

In order to address the question of whether or not spatial attention is

sustained when ISI is short (i.e., when dynamic change detection occurs),

we used a flicker change detection task in which pre- and postchange images

are presented repeatedly. We manipulated the ISI, i.e., the duration of a black

blank interval separating original and changed images. We also orthogo-

nally varied the spatial location of original and changed images. The flicker

change detection task allowed observers to serially encode and compare

small sections of a scene (Yokosawa & Mitsumatsu, 2003), and they were not

forced to encode and compare large amounts of scene information (see

Varakin & Levin, 2008). To use the flicker change detection task minimizes

the possibility that observers scatter attention over spatial locations at a

given time; instead, it encourages them to focus and sustain attention on a

local area at a particular point at one time. Further, in the flicker change

detection task, when a change was detected, the viewers’ eyes were more

likely to be fixated on the changing object than any other location of the

scene, suggesting that a close link exists between fixation position (correlated

with focal attending locus) and change detection (Hollingworth, Schrock, &

1 It may be better to record eye movement to judge whether or not attention is sustained,

because eye movement correlates with attention movement in a normal scene viewing. However,

we cannot determine whether or not attention maintains its state using eye movement

measurements. Ariga et al. (2011) reported that observers do not maintain an attentional state

during a long blank display, even though the visual stimuli were always presented at the local

area where the observers can view the stimuli without eye movements. We are interested in the

issue of whether or not attention can maintain its state. Therefore, we did not record observers’

eye movements in this study.

4 NAKASHIMA AND YOKOSAWA

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

Henderson, 2001). Based on this suggestion, we assumed that detection in

the flicker change detection task is successful when an observer’s attention is

focused on the changing object. In addition, the images of object arrays

(used as stimuli) also encouraged observers to focus the attention on a local

area, because the presented objects were spatially segregated (i.e., they werenot spatially continuous).

The blank display separating original and changed images was black and

it differed in colour from the background of the array of object images.

This manipulation was designed to reduce the likelihood of iconic memory

(i.e., sensory persistence) influencing change detection. The operating as-

sumption is that because sensory persistence is highly susceptible to

interference from new sensory processing (see Hollingworth, 2006, 2008), a

background colour change during the ISI would serve as a type of backwardmask, preventing sensory persistence of the original image.

Before this experiment, we conducted a pilot experiment in order to

confirm whether the impression of ‘‘seeing the change occur’’ depends on ISI.

In the pilot experiment, 10 observers, who did not participate in Experiment 1

and 2, saw the original and changed image display presented by the flicker

paradigm, and evaluated the impression of ‘‘seeing the change occur’’.

The changing object was specified at the beginning of each trial, and

observers were instructed to fixate and attend to it. The original image display(250 ms) was alternated with the changed image display (250 ms), with a black

blank display inserted between image displays (i.e., ISI). After the presenta-

tion of image displays, participants were told to evaluate their impression

of ‘‘seeing the change occur’’ by choosing a number from 0, 1, 2, 3, which

indicate the strength of the impression (from 0 �no impression to 3 �strong

impression). We used 12 ISI conditions (100, 200, 300, 400, 500, 600, 700, 800,

900, 1000, 1500, and 2000 ms) to comprehensively examine ISI effects. The

results replicated Hollingworth’s experiment (2008), suggesting that theexperience of seeing dynamic change arises in situations where an original

and a changed scene images are separated by a short ISI.

Following Hollingworth (2008) and our pilot experiment, we used a short

(ISI of 200 ms) and a long (ISI of 1000 ms) duration of the blank display.

We also manipulated the location of original and changed images using

no-shift and shift conditions. In the no-shift condition, original and changed

images were presented at the same spatial location, conforming to a typical

format of the flicker change detection task (e.g., Rensink et al., 1997;Yokosawa & Mitsumatsu, 2003). In the shift condition, original and changed

images were presented at entirely different locations, thereby forcing

attention focused upon one local area to move to a different spatial area.

If spatial attention is associated with a sustained focus upon a single local

area throughout the duration of a blank display, then change of image

location, as described earlier, should interfere in change detection. This is

SUSTAINED ATTENTION AND CHANGE DETECTION 5

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

due to the high cognitive cost to a viewer who must both disengage attention

from the original location, and move-plus-refocus attention upon a new

(changed) area in order to detect an object change. Otherwise if spatial

attention cannot be focused upon a single local area during a blank display,

postulating a cognitive cost for disengaging attention is unnecessary. Thus,this leads to an attenuation of the performance declining of change detection

in the shift condition. Several studies imply that attention can be sustained

for a brief time (e.g., Ariga et al., 2011; Duncan et al., 1994; Posner & Cohen,

1984; Raymond et al., 1992; Theeuwes et al., 2004). Accordingly, Experiment

1 examines a resulting prediction of an interaction between an image shift

manipulation the ISI: The decline of change detection performance in the

shift condition should be larger with short ISIs than with long ISIs.

Method

Participants. Twelve undergraduate and graduate students (mean age�23.17 years) with normal or corrected-to-normal vision participated. All

were naive with respect to the purpose of the research.

Stimuli. We chose 88 familiar objects (the object set) from commercial

three-dimensional model data sets (Figure 1). Eight objects were used for the

practice session, and remaining 80 objects were used for the experimental

session. The objects belonged to several categories: Animal, food, vehicle,

plant, tool, clothes, and furniture. The objects were rendered into colour

stimuli pictures (the original object images). Each object picture stimuli

subtended a maximum visual angle of 48�48. The background was uniformlygrey. An orientation change object image was created by transforming the

object using a mirror image reversal. A token change object image was the

image of a visibly different object from the same basic-level category used for

the original image, i.e., a token (Hollingworth & Henderson, 2002; see also

Archambault, O’Donnell, & Schyns, 1999).

In a display of the original images, eight original object images were

chosen randomly from the object set and arranged in a circle on the uniform

grey background square image (208�208). The radius of the circle was 88. Tocreate a changed image display, one of the objects in the original image

display was randomly selected as a target and replaced either by an orien-

tation transformation or by a token change object image. The location of the

changing object was counterbalanced.

Apparatus. Presentation of stimuli and recordings of participants’ res-

ponses were controlled by ViSaGe (Cambridge Research Systems). Stimuli

were displayed at a resolution of 1024�768 pixels by 24-bit colour on a

22-inch monitor.

6 NAKASHIMA AND YOKOSAWA

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

Procedure. Participants were seated in front of a computer monitor in a

dark room, and a viewing distance was fixed at 57 cm. On each trial, after

presentation of a fixation (1000 ms) display, then a blank display (1000 ms),

the original image (250 ms) alternating with a particular orientation or tokenchange image (250 ms) were presented. All the trials contained an object

change. Alternations occurred repeatedly, separated temporal by the blank

display (the flicker presentation; Figure 2). The flicker presentation sequence

was repeated until a participant detected the change between the two images,

or until a time out (13.5 s in the 200 ms ISI condition and 37.5 s in the

1000 ms ISI condition).

Participants were informed that all trials had one change object and

instructed to search for a changed object on each trial. They were told to pressa response button on discovery of a change, and then identify the changed

object in the test display including four original object images chosen

from the object presented in the flicker presentation display (4AFC test

display). When participants fail to find a changed object during the

flicker presentation, the instruction ‘‘Press a Button’’ was presented and

they were instructed to press a response button and choose one of the four

objects based on intuition. Reaction times (RTs) over time limits were

recorded as being of time limit duration (i.e., 13.5 s in the 200 ms ISIcondition and 37.5 s in the 1000 ms ISI condition). No feedback was given in

the experiment.

Conditions. In addition to the change type (orientation change, token

change), the four main conditions involved two variables (ISI, shift). Two ISIconditions corresponded to presentation of a blank display (black in colour)

for either an ISI of 200 ms or 1000 ms, respectively. The flicker presentation

durations were at most 13.5 s in the 200 ms ISI condition and 37.5 s in the

1000 ms ISI condition. Two shift conditions were shift and no-shift. The shift

condition changed the location of the object between the original image

display and changed image display, whereas the no-shift condition did

Figure 1. Sample object stimuli in this study. Samples of original objects (upper row) and their token

change objects (lower row). Stimuli were presented in colour.

SUSTAINED ATTENTION AND CHANGE DETECTION 7

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

not. The original image was always presented at the centre of the display. In

the shift condition, the changed image was shifted by 48 from the original

image; thus the original and changed object images were presented at a

completely different location. The changed image was shifted to one of the

four different directions (up, down, right, and left), chosen randomly at the

beginning of each trial in the shift condition. Four possible shift directions

ensured that participants could not predict the direction of the shift. That

is, every flicker in the shift condition contained a shift of the images from

one spatial location to another. In the no-shift condition, the original and

changed images were presented at the same spatial location (i.e., the centre of

the display).

Figure 2. Sequence of events (flicker presentation) for sample trials in Experiment 1. Each sequence

was repeated until a participant detected the change between the two images; in this case the change

was a token change: One cup is replaced by another. Two shift conditions were no-shift condition, in

which two images were presented at the same location (left of the changed image), and shift condition,

in which two images were presented at the different location (right of the changed image); in this case

the shift direction was ‘‘right’’.

8 NAKASHIMA AND YOKOSAWA

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

Participants completed an experimental session of 256 trials, 32 in each of

the eight conditions created by the 2 (200 ms, 1000 ms ISIs)�2 (no-shift,

shift)�2 (orientation, token change) factorial design. The ISI conditions

were blocked, and block order was counterbalanced across participants.

Within a block, the order of shift and no-shift trials (and other variables) wasdetermined randomly. In each block, participants first completed a practice

session of eight trials, one in each of the eight conditions.

Results

We assumed that participants concentrated on the change detection task,

because in each of the four main conditions the mean accuracy of identify-ing a changed object was quite high (above 95%). In the RT data analysis,

we used the mean number of alternations (proportional to the RT; Rensink,

2000c), to compare the performance across the four main conditions. The

mean number of alternations was taken only from correct detection res-

ponses (i.e., the trials in which participants could choose a changed object

from the 4AFC test display). Before the RTs for the correct responses were

analysed, the outliers which were more than 2.5 SDs from the mean in each

participant were removed. As the result, 2.6% of the trials, which included alltime-out trials, were removed.

Figure 3 shows the results of Experiment 1 collapsed over the change

type conditions, because there were no interaction between change type and

the other conditions. We conducted a repeated measures ANOVA with the

factors of ISI, shift, and change type. There were significant effects of shift,

F(1, 11)�41.42, MSE�0.23, pB.001, and change type, F(1, 11)�14.45,

MSE�0.43, pB.003. Performance in the shift condition was poorer (i.e.,

slower) than in the no-shift condition,2 and performance in the orientationchange condition was poorer than in the token change condition. Further,

a significant interaction of ISI with shift was observed, F(1, 11)�51.08,

MSE�0.13, pB.001.

Post hoc analyses followed up on the interaction of ISI and shift.

Performance in the shift condition was poorer in the 200 ms ISI condition,

pB.001, but there were no differences due to shift in the 1000 ms ISI

condition, p�.7. Therefore, as a matter of course, performance decline with

an image shift, calculated by the number of alternations in shift condition

2 We conducted an additional analysis to examine the effect of the image shift orientation.

We divided the data of shift conditions in both ISI conditions into two groups based on the

image shift (vertical shift and horizontal shift). An ANOVA revealed that only the main effect of

ISI was significant, F(1, 11) �4.89, MSE�0.99, pB.05. Neither the main effect of image shift

orientation nor shift type with ISI interaction were significant, Fs B1, MSEs �0.9, ps�.4. We

did not obtain an effect of the image shift orientation. One explanation for this is that the effect

is likely to be very small because the degree of the image shift (48) was relatively small.

SUSTAINED ATTENTION AND CHANGE DETECTION 9

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

minus the number of alternations in no-shift condition, was larger in the 200

ms ISI condition (1.17) than in the 1000 ms condition (0.10), t(11)�7.17,

pB.001. In addition, in the no-shift condition, performance was signifi-

cantly better (faster) in the 200 ms ISI condition than in the 1000 ms ISI

condition, pB.003, whereas the performance in the shift condition was

significantly poorer (slower) in the 200 ms ISI condition than in the 1000 ms

ISI condition, pB.001. Other main effects and interactions were not

significant, Fs B1, MSEs �0.19.

Discussion

Participants were slower to detect an orientation change than to detect a

token change. This result is consistent with the assumption that orientation

changes are more difficult to detect than token changes, because object

identity is invariant under an orientation transformation, but it is not under

a token change (e.g., Hollingworth & Henderson, 2002; Nakashima &

Yokosawa, 2011).

Shifting the location of a changed image also lowered performance. This

agrees with previous findings that change detection is poorer when the object

is presented in a new location (e.g., Blackmore, Brelstaff, Nelson, &

Troscianko, 1995). Presumably this is due to the fact that observers must

refocus spatial attention to the new locus of the object in order to compare

the new input information with the representation of a prechange (i.e.,

original) object. Indeed, in this experiment the 200 ms ISI resulted in slower

change detection performance to a shifted image. By contrast, in the 1000 ms

ISI, this was not the case. The interaction of shift with ISI observed in

Experiment 1 indicates that attention can be sustained during a brief time

period (e.g., 200 ms). In the 200 ms ISI condition, attention is focused on the

8

7

6

5

4

3

2

1

0200 ms 1000 ms

ISI condition

No-shiftShift

Alte

rnat

ions

Figure 3. Experiment 1: Mean alternations as a function of ISI and shift condition. Error bars are

standard errors of the means.

10 NAKASHIMA AND YOKOSAWA

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

area occupied by an object (or perhaps multiple objects), and sustained at

this location throughout this period. But when an image shift occurs,

attention will be forcibly disengaged to refocus on the object at a different

location. Theoretically, this reorientation should take additional time. The

1000 ms ISI, by contrast, disengagement can occur spontaneously during thepresentation of a blank display. Even if an image shift occurs, attention can

be refocused on the object at the different location with a lower cognitive

cost, because the cost for disengagement is not necessary. The finding that

people were somewhat faster in detecting a change with the 200 ms ISI

condition than with the 1000 ms ISI condition in the no-shift condition also

provides evidence to support this claim. This is because with 1000 ms ISI it is

difficult to sustain attention for that duration and then attention should be

refocused upon the same exact region. Therefore, in the no-shift condition,the change detection performance decreased because of this cognitive cost

(i.e., the cost of refocusing attention on the object location).

Before we conclude that focused attention is sustained only for a short

period of blank time, we should consider alternative explanations of these

findings that do not appeal to limits on sustained attending. First, one such

explanation assumes that the time for consolidation of object memory can

selectively influence performance in the shift condition. Visual memory

performance has been shown to increase with longer view times, at least upto 5 s. This occurs not only with longer durations of a presented object, but

also with longer blank durations following a presented object (Tversky &

Sherman, 1975). In Experiment 1, time for memory consolidation may be

restricted with the short ISI condition but not with the long ISI condition.

This raises the possibility that a visual object representation is fragile and

affected by the image shift only in the short ISI condition. However, this

memory consolidation account incorrectly predicts that change detection

performance in the no-shift condition should be worse in the short ISIcondition than in the long ISI condition. This is because putatively visual

memory is not consolidated in the short ISI condition. This prediction is

inconsistent with our finding showing an opposing outcome. Specifically

change detection performance was better in 200 ms ISI condition than in

1000 ms ISI condition when the image shift did not occur. Therefore, we

rejected this possibility.

Another alternative explanation maintains that attention is captured by

a transient signal produced by a change. Although we used a black blankdisplay between two successive image displays, the masking effect of this

display may be weak. This leads to the conclusion that a transient change

signal captures attention only in the short ISI condition. This possibility can

explain the result that the image shift manipulation caused deterioration in

change detection performance in the short ISI condition. That is, a transient

signal created by an object change can only be generated in the no-shift

SUSTAINED ATTENTION AND CHANGE DETECTION 11

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

condition with a short ISI. However, if this is the case, we would expect to

find best performance in the no-shift condition with the short ISI, whereas

performance in the remaining three conditions should show comparable, and

poorer, performance because the transient change signal appears only in the

no-shift condition with short ISIs. This prediction, too, is inconsistentwith our results which showed that performance in the shift condition was

better with long ISIs than with short ISIs. Therefore, we also rejected this

possibility.

Third, we considered the effect of verbal encoding. In this study, because

we did not incorporate a verbal suppression task, it is possible that a verbal

representation of an object influenced change detection performance. For

instance, if participants can verbally encode an object representation when

given sufficient time, as in long ISI condition, they should perform betterthan those in the short ISI condition will limits encoding time. Perhaps

change detection performance can be impaired by the image shift only in

conditions wherein participants cannot encode verbally the image. In this

case, verbal encoding has an additional effect to visual encoding. This leads

to the prediction that overall change detection performance in the long

ISI condition would be better than in the short ISI condition. However, we

did not observe a main effect of ISI in this experiment. Furthermore, several

studies using change detection tasks (e.g., Hollingworth, 2003; Nakashima& Yokosawa, 2011) indicated that there was little or no effect of verbal

encoding in an orientation or token change detection. Further, no par-

ticipants in this study reported that they had encoded visual objects verbally

in the task. Therefore, we concluded that verbal encoding cannot be a main

factor for the results in this experiment.

In summary, the results of Experiment 1 suggest that attention focused

on an area is sustained only for a brief period of time (e.g., 200 ms). Further,

change detection when attention was sustained appeared to be facilitatedcompared with when attention was not sustained. Although performance in

the short ISI condition was significantly better than in the long ISI condition

in the no-shift condition, this difference was not, practically speaking, very

large. The degree of facilitation (the difference of alternation between two

ISI conditions) was less than one alteration. One reason why the facilitation

was small may relate to task difficulty. In this experiment, only eight discrete

objects, which were separated spatially, were presented in each trial.

Although this manipulation was necessary to examine the effect of sustainedattention, at the same time, it made the task relatively easy. As the result,

the degree of facilitation may have been quite small. In this study, we empha-

sized the fact that there was facilitation of change detection by sustained

attention, and did not discuss the absolute degree of facilitation further.

Taken together with the fact that observers reported a strong impression

12 NAKASHIMA AND YOKOSAWA

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

of seeing a dynamic change transpire at this focal area with a short ISI con-

dition, such sustained attention also appears to be related to the experience

of seeing dynamic change.

EXPERIMENT 2

The results of Experiment 1 suggest that focused attention is sustained

only for a short period of blank time, and is spontaneously disengaged during

a long blank time. Building on this, we sought to examine certain related

issues. One issue raises the question: Can viewers strategically control the

sustainment and disengagement of attention within a short blank time? In

Experiment 2 we address this question. We examine whether or not sustained

attention is independent of observers’ strategies or attentional settings.

In Experiment 1, shift and no-shift trials were randomly interleaved. It is

possible that the brief ISI conditions in Experiment 1 led observers to

consistently rely upon on a strategy whereby they focused attention on the

prechange (i.e., original) location of a presented object. This is because such a

strategy would at least be effective on no-shift trials, i.e., assuming observers

had not been instructed beforehand about the postchange object location. By

contrast, with longer ISI conditions, there is sufficient time for an observer to

decide whether they would focus attention on the same location or shift to the

different location. Thus, performance differences due to ISI in Experiment 1

may be the result of different strategies employed by participants in that

experiment.

In Experiment 2, we manipulated the shift/no-shift conditions as a

between block factor, in order to examine the observers’ intentional controls

of the sustained attention. If observers can control sustained attention even

with short ISI and the results of Experiment 1 were simply based on observer

strategies, then poor performance on shift trials with brief ISIs in that

experiment should be attenuated in Experiment 2. This is because blocking

levels of the shift variable will enable observers to know in advance if a trial

involves a shift in location or not. This knowledge should reduce the cog-

nitive cost or time spent determining whether or not they must disengage

attention. In this experiment, we assessed performance only for the 200 ms

ISI condition. This is because our aim was to examine whether the decline in

performance for shift conditions could be reduced. Participants were not

informed about the image shift direction beforehand, because participants in

Experiment 1 did not have advance knowledge of image shift direction. In

Experiment 2, we aimed to duplicate conditions used in Experiment 1 with

respect to shift manipulated. In other words, in both experiments the idea

SUSTAINED ATTENTION AND CHANGE DETECTION 13

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

was to eliminate any additional effects due to participants’ knowledge about

the shift direction3.

Method

Participants. Twelve undergraduate students (mean age �20.58 years)

with normal or corrected-to-normal vision participated. No one participatedin Experiment 1. They were naive with respect to the purposes of the

research.

Stimuli and apparatus. The stimuli and apparatus were identical toExperiment 1.

Procedure. The procedure of Experiment 2 was identical to Experiment 1,

with two exceptions. First, only the 200 ms ISI condition was used in thisexperiment. Second, we manipulated the shift/no-shift condition as a between

block factor in addition to retaining it as a within block factor. The within

block shift/no-shift factor condition was identical to that of Experiment 1;

shift or no-shift conditions were randomly determined at the beginning of

each trial. The between block shift/no-shift factor condition involved

presenting these two conditions in different blocks; in addition, participants

were informed beforehand as to whether the task was in the shift or no-shift

condition.Participants completed an experimental session of 256 trials, 32 in each

of the eight conditions created by the 2 (within, between block factor)�2

(no-shift, shift)�2 (orientation, token change) factorial design. The block

factor conditions were blocked, and block order counterbalanced across

participants. Further, in the between block factor condition, the shift/no-

shift condition order was counterbalanced across participants. Within a

block, trial order was determined randomly.

Results and discussion

As in Experiment 1, we assumed that participants concentrated on the

change detection task because of the high accuracy observed in each

3 We recognize that it is easier to shift attention to a different location when participants

know the direction of the shift beforehand. Although this issue is very important, we were

concerned that participants’ knowledge about the shift direction might have an additional

influence on change detection in this study, because this manipulation could reduce the

cognitive cost of not only disengaging attention but also shifting attention to a particular

direction. Thus, we did not give instructions regarding the shift direction, in order to focus on

the effect of the cognitive cost of disengaging attention during a blank display. We plan to

pursue this issue in future research.

14 NAKASHIMA AND YOKOSAWA

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

condition (above 95%). We analysed the mean number of alternations, which

were taken only from correct responses. In the same manner as in

Experiment 1, we removed the outliers (2.8%, including all the time-out

trials), which were more than 2.5 SDs from the mean in each participant

before the RTs for the correct responses were analysed.

Figure 4 shows the results of Experiment 2 collapsed over change type

conditions, because there were no interaction between change type and

the other conditions. We conducted a repeated measures ANOVA with the

factors of block factor, shift, and change type. There were significant

effects of shift, F(1, 11)�61.75, MSE�0.86, pB.001, and change type,

F(1, 11)�8.15, MSE�1.15, pB.02. Performance in the shift condition

was poorer (slower) than in the no-shift condition, and performance in the

orientation change condition was worse than in the token change condition,

replicating the results of Experiment 1. However, other main effects and

interactions were not significant, Fs B2, MSEs �0.06. In particular, dif-

ferences due to the block factor were not statistically significant.

These results show that poor change detection occurs for spatially shifted

postchange objects in both the within block and between block shift

conditions. In other words, blocking shift and no-shift trials did not

facilitate performance on the shift trials with brief ISIs when compared to

performance in the within block condition which mixed the two types of shift

trials. Statistically, the decline of performance by the image shift did not

differ as function of blocking condition (within; 1.57, between; 1.41),

t(11) �0.59, p�.5. This implies that prior knowledge of the trial shift

type did not reduce the decline in performance on trials with spatial shifts of

critical objects.

8

7

6

5

4

3

2

1

0Within Between

Block factor condition

No-shiftShift

Alte

rnat

ions

Figure 4. Experiment 2: Mean alternations as a function of the block factor and shift condition.

Error bars are standard errors of the means.

SUSTAINED ATTENTION AND CHANGE DETECTION 15

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

In sum, observers could not control the sustainment and disengagement

of attention during a short blank time. These findings suggest that attention

is automatically sustained during a short period of time, and support our

suggestion that sustained attention is related to the experience of seeing

dynamic change.

GENERAL DISCUSSION

The purpose of the present study was to examine whether attention focused

on an area is sustained only for a short blank time, in which the experience

of seeing dynamic change occurs, using a flicker change detection task

(Rensink et al., 1997; Yokosawa & Mitsumatsu, 2003). In Experiment 1, we

manipulated the ISI between an original and a changed image as well as

varying the location of a target object across the original and changed imagedisplays (the image shift variable). Participants performed most poorly when

the ISI was brief and the changed image was shifted. These results indicate

that attention, which is focused upon a local area, appears to be sustained at

that area for only a brief period of time. In Experiment 2, where blocking of

no-shift and shift conditions was examined, participants were putatively

aware of the object shift in the shift condition. In this experiment,

participants continued to show poor performance due to an image shift,

indicating that prior knowledge of a shift did not dispel the poorperformance participants showed on shift trials. This result indicates that

observers cannot control the sustainment of attention during the short blank

time. Taken together, results indicate that attention must be sustained for a

short time during a blank display.

The idea that attention is sustained for short periods of time is consis-

tent with the suggestions of several previous studies (e.g., Ariga et al., 2011;

Duncan et al., 1994; Posner & Cohen, 1984; Raymond et al., 1992; Theeuwes

et al., 2004). In particular, it is difficult to maintain attentional state duringthe blank display (Ariga et al., 2011). The present study expands the

suggestion that attention is automatically sustained for short periods of time,

especially for short periods of blank time, to change detection tasks.

The present study suggests that attention focused on a local area can be

sustained for a short time during blank display in the change detection task.

Further, this implies that change detection which occurs within a focal

region during a period of sustained attention can be facilitated; this is

evident in results of Experiment 1. These results are consistent with thestudy reporting that attentional shift to a changed object facilitates change

detection (Smith & Schenk, 2008; see also Scholl, 2000). However, they

examined the effect of a reflexive attentional shift that is captured by a

peripheral visual event, and not the intentional attentional shift of interest in

16 NAKASHIMA AND YOKOSAWA

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

the present study. Thus, this study suggested that attention can facilitate

change detection regardless of whether the attention is a reflexive or an

endogenous process. Furthermore, the results in this study are consistent

with findings that a long blank duration (e.g., 320 ms) renders change

detection performance poorer in the flicker paradigm (Rensink, O’Regan, &

Clark, 2000). Although Rensink et al. (2000) did not discuss the relationship

between the blank duration and sustained attention in detail, their results

can be explained by our suggestion that attention can be sustained for a

short time and, when present, this persistence of attention, in turn,

facilitates change detection (i.e., attention tends not to be sustained for

the blank duration of 320 ms).

Additionally, considering the fact that observers report strong impres-

sions of seeing a dynamic change occur over a short ISI condition in both

Hollingworth (2008) and in our pilot experiment, any facilitation of change

detection discovered using short ISI is likely to be based upon sustained

attention. Contrary to our suggestion, Hollingworth claimed the difference

in impression of change as function of ISI cannot be explained by attention.

His claim is based on the fact that observers were attending to the change

object that was specified at the onset of a trial. The difference between

suggestions offered by Hollingworth and our interpretation of attention in

the present study stems from different definitions of ‘‘sustained attention’’.

Hollingworth defined sustained attention in terms of focused attention on

specific object when it was presented. This definition is consistent with that

of Nakayama and Mackeben (1989), who suggested that observers could

always direct their attention easily to the optimal location when a critical

target was presented at the same location in every trial. By contrast, our

definition of sustained attention maintains that attention is a state that is

maintained at a particular spatial region (i.e., not object specific) such that it

persists throughout a blank duration. In Hollingworth’s experiment, it is not

clear whether attention can maintain its state throughout a blank display,

i.e., in the absence of an object. According to our view, attention can be

sustained with its state lasting a short period of time in the absence of an

object. Therefore, we conclude that sustained attention is involved in the

experience of seeing dynamic change. In turn, this engagement of attention

contributes to the strong impression people have of ‘‘seeing’’ a change

actually occur. This means that sustained attention can be related to the

experience of seeing dynamic change.

In conclusion, although there remained some issues that have not been

clarified completely and should be examined, we suggest that the difference

between the experience of seeing dynamic change and that of detecting a

completed change is not merely a phenomenological difference. Instead,

SUSTAINED ATTENTION AND CHANGE DETECTION 17

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

these two experiences are distinguished, respectively, by the presence and

absence of sustained attention.

REFERENCES

Archambault, A., O’Donnell, C., & Schyns, P. G. (1999). Blind to detect changes: When learning

the same object at different levels of categorization modifies its perception. Psychological

Science, 10, 249�255.

Ariga, A., Kawahara, J., & Watanabe, K. (2011). Object-based maintenance of temporal

attention in rapid serial visual presentation. Visual Cognition, 19, 553�584.

Ariga, A., & Yokosawa, K. (2008). Attentional awakening: Gradual modulation of temporal

attention in rapid serial visual presentation. Psychological Research, 72, 192�202.

Blackmore, S. J., Brelstaff, G., Nelson, K., & Troscianko, T. (1995). Is the richness of our visual

world an illusion? Transsaccadic memory for complex scenes. Perception, 24, 1075�1081.

Duncan, J., Ward, R., & Shapiro, K. (1994). Direct measurement of attentional dwell time in

human vision. Nature, 369, 313�315.

Grimes, J. (1996). On the failure to detect changes in scenes across saccades. In K. Akins (Ed.),

Vancouver studies in cognitive science (Vol. 5, pp. 89�110). Oxford, UK: Oxford University

Press.

Hollingworth, A. (2003). Failures of retrieval and comparison constrain change detection in

natural scenes. Journal of Experimental Psychology: Human Perception and Performance, 29,

388�403.

Hollingworth, A. (2006). Visual memory for natural scenes: Evidence from change detection

and visual search. Visual Cognition, 14, 781�807.

Hollingworth, A. (2008). Visual memory for natural scenes. In S. J. Luck & A. Hollingworth

(Eds.), Visual memory (pp. 123�161). Oxford, UK: Oxford University Press.

Hollingworth, A., & Henderson, J. M. (2002). Accurate visual memory for previously attended

objects in natural scenes. Journal of Experimental Psychology: Human Perception and

Performance, 28, 113�136.

Hollingworth, A., Schrock, G., & Henderson, J. M. (2001). Change detection in the flicker

paradigm: The role of fixation position within the scene. Memory and Cognition, 29, 296�304.

Hollingworth, A., Williams, C. C., & Henderson, J. M. (2001). To see and remember: Visually

specific information is retained in memory from previously attended objects in natural

scenes. Psychonomic Bulletin and Review, 8, 761�768.

Mitroff, S. R., Simons, D. J., & Levin, D. T. (2004). Nothing compares 2 views: Change

blindness can occur despite reserved access to the changed information. Perception and

Psychophysics, 66, 1268�1281.

Nakashima, R., & Yokosawa, K. (2011). Does scene context always facilitate retrieval of visual

object representations? Psychonomic Bulletin and Review, 18, 309�315.

Nakayama, K., & Mackeben, M. (1989). Sustained and transient components of focal visual

attention. Vision Research, 29, 1631�1647.

O’Regan, J. K., Deubel, H., Clark, J. J., & Rensink, R. A. (2000). Picture changes during blinks:

Looking without seeing and seeing without looking. Visual Cognition, 7, 191�211.

O’Regan, J. K., Rensink, R. A., & Clark, J. J. (1999). Change blindness as a result of

‘‘mudsplashes’’. Nature, 398, 34.

Posner, M. I., & Cohen, Y. (1984). Components of visual orienting. In H. Bouma &

D. Bouwhuis (Eds.), Attention and performance X (pp. 531�556). Hove, UK: Lawrence

Erlbaum Associates.

18 NAKASHIMA AND YOKOSAWA

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012

Raymond, J. E., Shapiro, K. L., & Arnell, K. M. (1992). Temporary suppression of visual

processing in an RSVP task: An attentional blink? Journal of Experimental Psychology:

Human Perception and Performance, 18, 849�860.

Rensink, R. A. (2000a). The dynamic representation of scenes. Visual Cognition, 7, 17�42.

Rensink, R. A. (2000b). Seeing, sensing, and scrutinizing. Vision Research, 40, 1469�1487.

Rensink, R. A. (2000c). Visual search for change: A probe into the nature of attentional

processing. Visual Cognition, 7, 345�376.

Rensink, R. A. (2002). Change detection. Annual Review of Psychology, 53, 245�277.

Rensink, R. A., O’Regan, J. K., & Clark, J. J. (1997). To see or not to see: The need for attention

to perceive changes in scenes. Psychological Science, 8, 368�373.

Rensink, R. A., O’Regan, J. K., & Clark, J. J. (2000). On the failure to detect changes in scenes

across brief interruptions. Visual Cognition, 7, 127�145.

Scholl, B. J. (2000). Attenuated change blindness for exogenously attended items in a flicker

paradigm. Visual Cognition, 7, 377�396.

Simons, D. J., & Rensink, R. A. (2005). Change blindness: Past, present, and future. Trends in

Cognitive Sciences, 9, 16�20.

Smith, D. T., & Schenk, T. (2008). Reflexive attention attenuates change blindness (but only

briefly). Perception and Psychophysics, 70, 489�495.

Theeuwes, J., Godijn, R., & Pratt, J. (2004). A new estimation of the duration of attentional

dwell time. Psychonomic Bulletin and Review, 11, 60�64.

Tversky, B., & Sherman, T. (1975). Picture memory improves with longer on time and off time.

Journal of Experimental Psychology: Human Learning and Memory, 104, 114�118.

Varakin, D. A., & Levin, D. T. (2008). Scene structure enhances change detection. Quarterly

Journal of Experimental Psychology, 61, 543�551.

Yokosawa, K., & Mitsumatsu, H. (2003). Does disruption of a scene impair change detection?

Journal of Vision, 3, 41�48.

Manuscript received July 2011

Manuscript accepted January 2012

First published online February 2012

SUSTAINED ATTENTION AND CHANGE DETECTION 19

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

19:

44 1

4 Fe

brua

ry 2

012