ORIGINAL RESEARCH ARTICLE

published: 23 October 2013
doi: 10.3389/fpsyg.2013.00760

Imposed visual feedback delay of an action changes massperception based on the sensory prediction error
Takuya Honda 1,2 , Nobuhiro Hagura 1,3 , Toshinori Yoshioka 1 and Hiroshi Imamizu 1,4*
Cognitive Mechanisms Laboratories and Brain Information Communication Research Laboratory Group, Advanced Telecommunications Research InstituteInternational, Kyoto, Japan
2
Research Fellow of the Japan Society for the Promotion of Science, Tokyo, Japan
3
Institute of Cognitive Neuroscience, University College London, London, UK
4
Center for Information and Neural Networks, National Institute of Information and Communications Technology and Osaka University, Osaka, Japan
1

Edited by:
Makoto Miyazaki, Yamaguchi
University, Japan
Reviewed by:
R. Chris Miall, University ofBirmingham, UK
David Franklin, University ofCambridge, UK*Correspondence:
Hiroshi Imamizu, Advanced
Telecommunications ResearchInstitute International, 2-2-2
Hikaridai, Seika-cho, Soraku-gun,Kyoto 619-0288, Japane-mail: imamizu@gmail.com

While performing an action, the timing of when the sensory feedback is given can beused to establish the causal link between the action and its consequence. It has beenshown that delaying the visual feedback while carrying an object makes people feel themass of the object to be greater, suggesting that the feedback timing can also impact
the perceived quality of an external object. In this study, we investigated the origin of the
feedback timing information that influences the mass perception of the external object.
Participants made a straight reaching movement while holding a manipulandum. The
movement of the manipulandum was presented as a cursor movement on a monitor.
In Experiment 1, various delays were imposed between the actual trajectory and the
cursor movement. The participants’ perceived mass of the manipulandum significantly
increased as the delay increased to 400 ms, but this gain did not reach significance when
the delay was 800 ms. This suggests the existence of a temporal tuning mechanism
for incorporating the visual feedback into the perception of mass. In Experiment 2, we
examined whether the increased mass perception during the visual delay was due tothe prediction error of the visual consequence of an action or to the actual delay of the
feedback itself. After the participants adapted to the feedback delay, the perceived massof the object became lighter than before, indicating that updating the temporal prediction
model for the visual consequence diminishes the overestimation of the object’s mass.
We propose that the misattribution of the visual delay into mass perception is induced by
the sensorimotor prediction error, possibly when the amount of delay (error) is within therange that can reasonably include the consequence of an action.
Keywords: sensorimotor prediction, feedback delay, mass perception, delay adaptation, prediction error

INTRODUCTION
While performing an action, information on the timing of thesensory feedback has a crucial role in detecting the causal link
between the action and its consequence (Kitazawa et al., 1995;
Blakemore et al., 1999; Farrer et al., 2008; Tanaka et al., 2011;
Honda et al., 2012a,b). For example, when the visual feedback
is delayed, a self-generated visual motion is perceived as generated by someone else (Blakemore et al., 1999; Farrer et al.,2008). Furthermore, the motor learning process is also disrupted in such situations, possibly due to the failure of accurately linking the feedback information with one’s own action(Kitazawa et al., 1995; Tanaka et al., 2011; Honda et al., 2012a,b).
It has been suggested that the central nervous system (CNS)
uses a forward model to predict the sensory consequence of anaction (e.g., the position of the hand at a certain time point)
by using a copy of the motor command (Miall et al., 1993;
Wolpert et al., 1995; Miall et al., 2007). In such a scenario,
the amount of prediction error, which is the difference between
the predicted and the actual sensory feedback, contributes todetecting whether the sensory input is actually generated by the
person.

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The feedback timing information is not only used for linking
the action and the consequence but can also contribute to the perception of the external environment. For example, the perceptionof a somatosensory event induced by self-touch is modified whena delay is imposed between the action and the touch (Blakemore
et al., 1999). Likewise, it has been shown that delaying the visualfeedback of an action while carrying an object makes people feelthat the mass of that object is greater (Di Luca et al., 2011). Suchevidence suggests that delay in the sensory feedback of an action
may violate the authorship of the sensory consequence and, at thesame time, change the quality of perception of that sensory event.
In this study, we focus on the influence of feedback timing on theperceptual quality of the object’s mass. Similar to the violation of
authorship induced by the prediction error, in this case, the difference in the visually predicted hand position and the actual visualfeedback (prediction error) may also contribute to such an overestimation of the object’s mass. However, it is not yet clear whether
the prediction error or the actual delay itself plays the major rolein causing this phenomenon.
To test these two possibilities, we set up a reaching experiment
where participants made a straight reaching movement while

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Honda et al.

holding a manipulandum. The movement of the manipulandum
was presented as a cursor movement on a monitor, which allowed
us to impose various delays between the actual hand movement
and the visual cursor movement. In Experiment 1, we examined
the relationship between the amount of delay and the illusory
increase of mass. Since the authorship of the sensory consequenceis violated with a longer imposed delay between the action and theconsequence, (Farrer et al., 2008) we predict that the mass of themanipulandum will be perceived as heavier for a shorter delay but
not for a longer delay.
In Experiment 2, we investigated the effect of delay adaptation on the perceived mass. If the prediction error were thecause of the increase in perceived mass, reducing the prediction
error by adapting to the delay would alleviate the overestimation of the mass. On the other hand, if the actual delay werethe cause, the mass would be overestimated irrespective of theadaptation.

Feedback delay and mass perception

FIGURE 1 | Top-down view of twin visuomotor and haptic interface
system (TVINS). In Experiment 1, only the right-hand manipulandum wasused. In Experiment 2, both manipulanda were used. The horizontal screen
is illustrated as if it were transparent in order to show the manipulandum.
In reality, it was opaque and reflected images generated by the projector
installed above.

MATERIALS AND METHODSPARTICIPANTS

A total of 24 neurologically normal right-handed (Oldfield, 1971)
volunteers (22 males and 2 females; age range, 20–44 years) participated. The study was approved by the Ethics Committee ofthe Advanced Telecommunications Research Institute. Written
informed consent was obtained from all participants prior toperforming the experiments.
APPARATUS

Participants sat on an adjustable chair while grasping the handle of a twin visuomotor and haptic interface system (TVINS)(Figure 1). The participant’s forearm was secured to a support
beam on the horizontal plane. TVINS consists of two parallellinked, direct-drive floating manipulanda using air magnets.
Thus, the experiment can be conducted either by using only one
manipulandum or by using both at the same time. Each manipulandum was powered by two DC direct-drive motors controlled
at 2000 Hz. TVINS yielded a virtual mass (M) according to theequation of motion: M = F/a. Here F is a resistance force generated by TVINS in proportion to the handle acceleration (a). We
confirmed that the accuracy in online measurement of the acceleration was ±0.04 m/s2 even at the peak acceleration. We also
confirmed by measuring the resistance force with a spring scalethat TVINS could generate a target force with the precision of
0.1 Kgf. The position of the manipulandum was measured using
optical joint position sensors (4,800,000 pulse/rev). The positionof the hand (handle of the manipulandum) was projected on ahorizontal screen placed above the mechanical plane and below
shoulder level. The projector refresh rate was 75 Hz. The screen
prevented the participants from directly seeing their arm.
It should be noted that there was a slight time delay for theactual handle movement to be reflected as the cursor movement on the screen, due to the limitations of the computer’s dataprocessing speed. When the delay between the handle and the cursor movements was measured 10 times by a high-speed camera(600 Hz), it was found to be 42.5 ms (SD 2.4 ms) when aroundthe handle position near the body (around the “starting position”
in the experiments) and 41.8 ms (SD 2.4 ms) when at a distance

Frontiers in Psychology | Consciousness Researchfrom the body (around the “target position”). No significant
difference between the positions [t(18) = 2.11, p = 0.543] wasobserved. Since this delay is comparable across positions, andour interest was in the difference between the conditions, we
believe that this delay itself will not affect our results. In thefollowing, we describe the delay from this “baseline delay” butnote that an additional 42-ms delay always existed in all of theconditions.
EXPERIMENT 1

We tested how the difference in imposed visual delay between theactual movement and the cursor feedback information influences
the mass perception.
Task procedure

Fourteen volunteers participated. By making a reaching movement while grasping the manipulandum with their right hand,participants moved the cursor toward the target presented 10 cm
from the starting point on the screen. After the reaching movement, the handle automatically moved back to the starting
position. Participants judged the perceived mass of the manipulandum after each trial.
Three target locations were prepared. The middle target wasstraight ahead from the starting point, and the other two were20◦ rotated clockwise or counterclockwise around the starting
point from the middle target’s path. The peak velocity of thereaching movement was required to be within the range of
300–450 mm/s. A warning message appeared on the screen if the
movement velocity of the handle was faster (“Fast”) or slower(“Slow”) than the set velocity range. The mass of the manipulandum was varied from trial to trial by adding a resistive force
against the movement of the hand (see above). Nine mass values were prepared: 1, 2, 3, 4, 5, 6, 7, 8, and 9 kg. Furthermore,a variable delay was imposed between the cursor movement
and the actual movement of the hand in each trial, where this
delay was chosen from five values: 0, 100, 200, 400, or 800 ms.
The experiment investigated every combination between mass

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Feedback delay and mass perception

and delay (9 masses × 5 delays: 45 combinations). Each combination was repeated 15 times in random order. Consequently,
each participant carried out a total of 675 trials. The experiment
was divided into five 135-trial blocks, and the participants wereallowed to take a break between the blocks. After each reaching
movement, participants judged whether the mass of the manipulandum was greater or smaller than the average of all of themass values presented in the previous trials. This is a versionof the “method of single stimuli,” (Morgan et al., 2000) which
requires participants to use their internal criterion for the judgment. The accuracy of this method is comparable to, and evenmore accurate than, (Nachmias, 2006) the method that always
presents a standard stimulus as a comparison stimulus (Wearden
and Ferrara, 1995; Hagura et al., 2012). Moreover, this method
enables us to increase the number of trials for a given period oftime, which is crucial for reconstructing the psychometric function. The judgment (“lighter” or “heavier”) was made by pressing
one of two buttons with the left hand. Before the experiment,
participants practiced and experienced each mass 30 times inorder to familiarize themselves with the distribution of the input
mass.
Data analysis

Participants’ judgments of the masses were analyzed separately forfive imposed delays. Logistic regression was used to relate the percentage of “heavier” judgment to overall stimulus mass value foreach participant. The form of the function was
y=

1
x−α ,
1 + e( θ )where α is the mass value corresponding to the point of subjective equality (PSE, the 50% response level on the psychometricfunction) and θ provides an estimate of the mass discrimination
sensitivity. To estimate the parameters, the logistic function was
fitted to the judgment data of individual subjects by using a generalized linear mode as implemented in a MATLAB glmfit function(MathWorks, Natick, MA, USA). One-Way analysis of variance(ANOVA) with repeated measures was used to test the effect ofthe delay value on both the PSE and the discrimination sensitivity. Ryan’s multiple comparison tests were used to compare the0-ms delay condition with the other delay conditions. The threshold for statistical significance was set at p < 0.05 throughout thisstudy.
EXPERIMENT 2

In Experiment 1, we found that the perceived mass of the manipulandum significantly increases with the amount of imposed visualfeedback delay when the delay is in the short range, but notwhen it is in the longer range (see Results). Next, we examined
whether decreasing the prediction error for the feedback delay
would change this delay-induced overestimation of the object’s
mass.
Task procedure

Ten volunteers participated. There were two conditions: delay
condition and no-delay condition. In delay condition, participants

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were continuously exposed to the visual feedback delay whenreaching to a target with the manipulandum, whereas delay was
not imposed in no-delay condition (simple reach trials). Between
these reaching trials, the participants’ ability to perceptually
recognize the delay (delay awareness trials) and their perception of
the manipulandum mass (mass comparison trials) were measured.
The two conditions were performed by each participant on
two separate days. The order of the conditions was randomly
assigned to each participant: five of them performed no-delay condition first, while the others performed delay condition first. Eachcondition consisted of 404 trials, which were divided into four
101-trial blocks. Each block consisted of 87 simple reach trials, 5delay awareness trials, and 9 mass comparison trials. Participants
took short breaks between blocks. Note that the delay awarenessand mass comparison trials were identical between conditions.
Therefore, any conditional difference observed in these trials
would be due to the pre-exposure to the feedback delay occurring in the simple reach trials. The details of these different trial
types are explained below.
In simple reach trials, participants made a right-hand reaching
movement by moving the manipulandum toward the target thatappeared 15 cm from the starting position. The visual feedback
was delayed for 200 ms in delay condition, whereas no delay was
imposed in no-delay condition. The aim of simple reach trials was
to allow participants to adapt to the 200-ms delay in delay condition (and the lack of delay in no-delay condition). To maintainparticipants’ concentration, in one of 10 to 11 trials, the target
jumped to the 20◦ clockwise-rotated position immediately after
the onset of the reaching. The simple reach trials were distributed
pseudo-randomly in a block, where more than one simple
reach was conducted before delay awareness or mass comparison
trials.
In delay awareness trials (sequence A in Figure 2), after making
the right-hand reaching movement, participants were required toanswer whether they felt any delay between their hand and the
cursor movement. This trial was used to assess the change in perceptual sensitivity to the delay. Since we found in our pilot study
that the delay of 200 ms was easily detectable, the cursor delay indelay awareness trials was set to 150 ms to avoid any ceiling effect.
Finally, in mass comparison trials (see sequence B in Figure 2),
after making a right-hand reaching movement, participants wereasked to make the same straight reaching movement with theirleft hand. Then, they were asked to judge whether the right hand
was heavier or lighter than the left hand. The cursor delay was set
to 200 ms for the right-hand movement, and there was no cursor
presented for the left-hand movement. The mass value of all of
the right-hand reaches was set to 3 kg (this was also the case forsimple reach and delay awareness), while the mass was set to 1,
3, or 5 kg for left-hand reaches. This trial was used to evaluate
the perception of mass under the delay of visual feedback, in thesame manner used in Experiment 1. Since our aim was to extend
our findings in Experiment 1, which was performed with the righthand, the left hand was used only to present the reference mass forthe right hand.
Before delay awareness and mass comparison trials, participants
were instructed about which type of trial they were going toperform (see “announcement” in Figure 2).

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Honda et al.

Feedback delay and mass perception

A

Announcement

Right-hand reach
VelocityIn the next trial, answer
whether the cursor delayed
from the hand movement.

OK

Left-hand reach

AnswerVelocity OK
Cursor delayed?
YesNo

TargetLeft-hand cursor
Right-hand cursor
start circle

B

VelocityOK

VelocityOK

Velocity OK
Which was heavier?
Left
Right

In the next trial,
answer which is heavier,left or right handle.
No cursor
during reaching

Before the start of each trial(manipulandum at the starting
position; 5~7 sec)

for 2.5 sec

FIGURE 2 | Two types of trials in Experiment 2. The horizontal flow is thesequence of each trial; (A) Delay awareness trial in which subjects were asked ifthey felt any delay in cursor movements, and (B) mass comparison trials inwhich subjects were asked to judge whether the right- or left-hand movementfor 2.5 sec

time
Until participants’ answer

was heavier. The instruction was on the screen from the end of the last trial until
the onset of the next trial (target appearance). The yellow letters and arrows areused to explain each display, but they are not shown on the screen during theactual experiment.

Data analysis

For the delay awareness and the mass comparison trials, theprobability of judging the trial as “delayed” and that of judging the mass of the right hand “heavier” were calculated.
These values were compared between the delay and no-delay
conditions.

RESULTS
EXPERIMENT 1

The psychometric function in Figures 3A,B describes the participants’ judgment of mass as a function of actually delivered mass.
Figure 3A shows the psychometric function constructed for different imposed delays (0, 100, 200, 400, or 800 ms) of a representative participant, while Figure 3B shows that of the data averaged
across all participants. One-Way ANOVA with repeated measures
performed on the PSEs of different delay values showed a significant effect of delay on mass perception [p = 0.024, F(4, 52) =3.082]. Figure 3C shows a shift in PSE for each delay from thecase of 0-ms delay. The post hoc comparison performed from the0-ms delay condition showed that the PSE significantly shifted
toward the heavier side when the 200-ms delay (p = 0.030 after
correction with Ryan’s nominal significant level) or the 400-ms
delay (p = 0.038 after the correction) was imposed, but not when
the delay was 100 ms (p = 0.175 after the correction) or 800 ms(p = 0.175 after the correction). Moreover, One-Way ANOVA
with repeated measures performed on the discrimination sensitivity of different delay values showed no significant effect of delay[p = 0.130, F(4, 52) = 1.866; mean sensitivity (±SD) was 0.97 ±0.09 for a 0-ms delay, 1.11 ± 0.10 for a 100-ms delay, 1.02 ± 0.10
for a 200-ms delay, 0.94 ± 0.08 for a 400-ms delay, and 1.01 ±0.08 for a 800-ms delay]. This indicates that sensitivity to the mass
did not differ according to the delays. The results show that thevisual feedback delay significantly modifies the mass perceptionof the manipulandum but failed to reach significance for a longer
delay.

Frontiers in Psychology | Consciousness Research

FIGURE 3 | Results of Experiment 1. (A) Results are shown for a typicalparticipant. The mass value at which each curve crosses the 0.5 line is PSE
for each delay value. The red arrow indicates the shift of PSE for a 800-ms
delay from that for a 0-ms delay (see panel C). (B) Psychometric functions
are fitted to data averaged across participants. Average judgment rate
across participants was calculated for each mass value, and sigmoid
functions were fitted to the averaged rates. (C) For each delay, the shift of
PSE from that for a 0-ms delay is shown. Shifts were calculated for eachcursor delay and averaged across participants. Error bars indicate standard
error of measures across participants. *p < 0.05 according to Ryan’s
multiple (four) comparison tests for difference in PSE between 0-ms delay
and the other delay conditions.

EXPERIMENT 2

One participant was excluded from the analysis based on his
extremely slow reaction times, that is, initiation of the movement
onset from the target appearance was more than 1000 ms on
average, possibly due to a lack of concentration on the task.

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Feedback delay and mass perception

rate of delay awareness

0.8

B1.0

*

0.7

C

0.8

0.6

0.6

0.5
0.4

0.4

0.3
0.2

0.2

0.1

0

0

No-delay
condition

Delaycondition

1

2

3

Block number

4

Rate of ‘right hand heavier’ response

A

1

0.8

0.6

0.4

0.2

0

No-delay condition
Delay condition
1

3

5

Left hand mass [kg]

FIGURE 4 | Results of Experiment 2. (A) Average delay awareness acrossparticipants is shown in each condition. *p < 0.05 according to the paired
t-test. (B) Rate of the delay awareness is shown as a function of blocknumber. (C) Average judgment of “right hand heavier” across participants
is shown for each right-hand mass value in each condition. Error bars
indicate standard error of measures across participants.

For the delay awareness trials, the rate of delay awarenesswas significantly higher in the no-delay condition than in the
delay condition according to the paired t-test [p < 0.001; t(8) =6.468; Figure 4A]. Namely, participants tended to more accurately perceive the imposed 150-ms delay in the no-delay condition
compared to the delay condition. This indicates that repeatedexposure to the delay in the simple reach trials made the participants less sensitive to the delay. The lower sensitivity to thedelay after being exposed to the delay was already observed in
the first block of trials, and it continued throughout the experiment (Figure 4B). When we analyzed the data with a Two-Way
ANOVA, using the effect of block number along with the effect ofcondition (delay or no-delay), only a main effect of the condition[p = 0.0001, F(1, 8) = 47.059] was observed, without any main
effect of the block [p = 0.102, F(3, 24) = 2.313] nor of the interaction between the two factors [p = 0.592, F(3, 24) = 0.649]. These
results show that exposure to the delay seems to have an immediate impact on the delay sensitivity, and the effect was consistentthroughout Experiment 2.
Following this tendency, participants perceived the mass ofthe manipulandum as lighter in the mass comparison trials of
the delay condition compared to that of the no-delay condition(Figure 4C). Two-Way ANOVA with repeated measures showedsignificant main effects of the condition [p = 0.002, F(1, 8) =19.139] and the mass value [p < 0.001, F(2, 16) = 71.627], without any significant effect of interaction [p = 0.558, F(2, 16) =0.605]. This indicates that the adaptation to the delay induced
the insensitivity to the delay, and this was accompanied by theperception of smaller mass compared to when there was no adaptation. In other words, the perceived delay may play a critical rolein judging the mass of an object while making a movement.

DISCUSSION
We examined how imposing a delay between an action and its
visual feedback influences mass perception. In Experiment 1, participants felt that the manipulandum was heavier as the feedback
delay increased to 400 ms, but this effect was less clear when the
delay was 800 ms (Figure 3C). This indicates that mass perception
modified by feedback delay is not solely related to the amountof delay. The results of Experiment 2 show that the mass overestimation was alleviated when the participants adapted to thewww.frontiersin.org

delay, compared to when there was no adaptation (Figure 4C).
This suggests the sensory feedback prediction error may play animportant role in inducing the overestimation of mass.
Delaying the visual feedback during manual actions causes a
discrepancy between visual and proprioceptive positional estimates of the hand, or between expected and actual hand positions. This kind of discrepancy tends to be attributed to the massperception, making the participants feel that the hand-held object
is heavier than expected (Di Luca et al., 2011). Within the range ofthe delay investigated in the previous study (0–200 ms), the perceived mass linearly increased as the delay increased. However,this was not the case for much longer delays, which was specifically tested in our experiment (Figure 3C); when the delay was
800 ms, the effect of overestimating the mass became variable.
This shows that longer feedback delay is processed differently
from shorter delays. A previous study showed that delaying thetiming of a sensory consequence of an action makes people feelthat the time between an action and its sensory consequence isshorter than it actually is (Haggard et al., 2002). This binding
effect was regarded as an implicit measure of whether the sensory input is actually processed as one’s own action (authorshipof the sensory event) (Haggard et al., 2002; Haggard and Clark,
2003). Several studies have shown that the binding effect is modulated by temporal contiguity: When the feedback delay is large, thebinding effect becomes weak (Haggard et al., 2002; Heron et al.,2009). Many studies have demonstrated that such binding does
not occur if the delay is more than 200–300 ms (Blakemore et al.,
1999; Haggard et al., 2002; Heron et al., 2009). In considering thisevidence, the reason why the longer feedback delay (800 ms) was
not reflected as an increase in mass may be due to the disruptionof the association between an action and its sensory consequence:
The longer delay may have violated the authorship of the sensory feedback information rather than being processed as theconsequence of the action. Violation of action-authorship modifying the quality of the sensory perception may reflect findingsin the literature showing that the participant’s perceived intensity(amount of force) (Shergill et al., 2003) or the quality (ticklishness) of a tactile input depends on the applied timing of the tactile
stimulus in relation to the participant’s own action (Blakemore
et al., 1999).
It should be noted that the violation of the authorship of the
feedback information in the present study can occur without
depending on the amount of delay; since the average movement
time of reaching movement was 882 ± 88 ms, participants may
not have related the 800-ms-delay feedback to their own movement simply because the movement had nearly terminated. Ourcurrent experimental design cannot separate the effects of these
two factors, and so further study is needed to separate these
possibilities.
In Experiment 2, when the participants were repeatedly
exposed to the delay (delay condition), they became less sensitive to the delay compared to when not exposed to the delay(no-delay condition) (Figures 4A,B). Reduced sensitivity to thetemporal delay shows that the participants were perceptuallyadapted to the feedback delay in the delay condition, as has beenshown both in the perceptual domain (Haggard et al., 2002;
Haggard and Clark, 2003) and in the motor control domain

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Honda et al.

Feedback delay and mass perception(Honda et al., 2012a,b). Accompanying this adaptation effect, theillusory increase in mass was significantly alleviated in the delay
condition in comparison to the no-delay condition (Figure 4C; redplots are significantly below blue ones). This result clearly showsthat the mass overestimation accompanying feedback delay is notcaused by the actual delay itself, since the actual delay is constantin the two conditions (Figure 4C). Furthermore, this suggests thatthe factors changing in accordance with the perceptual temporal adaptation might be tightly linked to the alleviation of mass
overestimation.
Two different types of adaptation may underlie the temporal
adaptation observed between the action and the sensory input
in this study. One is the adaptation between different sensory
inputs, such as between vision and proprioception (Kambara
et al., 2013). Feedback delay will lead to a discrepancy between
the two, which may require calibration. The other possibility
is the involvement of a motor command, providing prediction
about the timing of the sensory reafference. In this case, adaptation may have occurred between the predicted and the actual
timing of the incoming sensory input (prediction error). Either
mechanism could have worked in our experiment. However,
Stetson et al. (2006) showed that the strength of calibration ofperceived timing between pressing a button and a visual flash

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Frontiers in Psychology | Consciousness Research

is much weaker when the button press was replaced by a passive button touch. Other studies on delay perception have alsosuggested that prediction in the sensorimotor system is critical for a change in temporal perception (Haggard and Clark,
2003; Stetson et al., 2006). Therefore, we believe that the increasein mass perception dominantly involves motor-based prediction error. In any case, further study is necessary to clarify thispoint.
In conclusion, we propose that the misattribution of a visual
delay to the increased mass perception is induced by the sensorimotor prediction error, and it seems to preferentially occur
when the delay is within the range that can be attributed to theconsequence of the action.

ACKNOWLEDGMENTS
The authors would like to thank Drs. Kenji Ogawa, Chang Cai,
Satoshi Hirose, and Mitsuo Kawato for their helpful comments,and Ms. Yuka Oshima for recruitment of the participants. This
research was supported by Grants-in-Aid for JSPS Fellows #229430 (Takuya Honda). Nobuhiro Hagura was supported by Marie
Curie International Incoming Fellowships. The funders had norole in the study design, data collection and analysis, decision to
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Conflict of Interest Statement: The
authors declare that the research
was conducted in the absence of any
commercial or financial relationshipsthat could be construed as a potential
conflict of interest.

Received: 19 June 2013; accepted: 28
September 2013; published online: 23
October 2013.
Citation: Honda T, Hagura N, Yoshioka
T and Imamizu H (2013) Imposed visualfeedback delay of an action changes massperception based on the sensory prediction error. Front. Psychol. 4:760. doi:
10.3389/fpsyg.2013.00760
This article was submitted to
Consciousness Research, a section of
the journal Frontiers in Psychology.
Copyright © 2013 Honda, Hagura,
Yoshioka and Imamizu. This is an
open-access article distributed under
the terms of the Creative Commons
Attribution License (CC BY). The use,
distribution or reproduction in otherforums is permitted, provided the original author(s) or licensor are credited and that the original publicationin this journal is cited, in accordancewith accepted academic practice. No use,
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