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Cited by 499Virtual Reality Applications and ImpactsMultisensory perception and integrationFree Will and Agency

Extending body space in immersive virtual reality: a very long arm illusion

Open access
Kilteni, Konstantina, Normand, Jean-Marie, Sanchez-Vives, Maria V., Slater, Mel·2012·PLoS ONE
DOI 10.1371/journal.pone.0040867PMC PMC3400672
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Abstract

Recent studies have shown that a fake body part can be incorporated into human body representation through synchronous multisensory stimulation on the fake and corresponding real body part - the most famous example being the Rubber Hand Illusion. However, the extent to which gross asymmetries in the fake body can be assimilated remains unknown. Participants experienced, through a head-tracked stereo head-mounted display a virtual body coincident with their real body. There were 5 conditions in a between-groups experiment, with 10 participants per condition. In all conditions there was visuo-motor congruence between the real and virtual dominant arm. In an Incongruent condition (I), where the virtual arm length was equal to the real length, there was visuo-tactile incongruence. In four Congruent conditions there was visuo-tactile congruence, but the virtual arm lengths were either equal to (C1), double (C2), triple (C3) or quadruple (C4) the real ones. Questionnaire scores and defensive withdrawal movements in response to a threat showed that the overall level of ownership was high in both C1 and I, and there was no significant difference between these conditions. Additionally, participants experienced ownership over the virtual arm up to three times the length of the real one, and less strongly at four times the length. The illusion did decline, however, with the length of the virtual arm. In the C2-C4 conditions although a measure of proprioceptive drift positively correlated with virtual arm length, there was no correlation between the drift and ownership of the virtual arm, suggesting different underlying mechanisms between ownership and drift. Overall, these findings extend and enrich previous results that multisensory and sensorimotor information can reconstruct our perception of the body shape, size and symmetry even when this is not consistent with normal body proportions.

AI snapshot

Written from the paper’s full text.

TL;DR

In an immersive virtual reality between-groups experiment, participants experienced ownership over a virtual arm elongated up to three times the real arm length, with the illusion declining at four times. Ownership and proprioceptive drift appeared to depend on different underlying mechanisms.

Key findings

  • With no elongation, ownership was high in both congruent (C1) and visuo-tactile incongruent (I) conditions: Q3 median was 4/5 in both, P = 1.0000, while touch-referral Q1/Q2 were significantly higher in C1 (P = 0.0009 and P = 0.0001).
  • Ownership declined with virtual arm elongation: ordered logistic regression of Q3 on elongation had a negative coefficient, P = 0.032; estimated probabilities of Q3 ≥ 4 were 0.86, 0.78, 0.66, and 0.52 for elongations 1–4, leaving about a 50% chance of high ownership at four times real length.
  • Proprioceptive drift was positively associated with elongation (Spearman P = 0.03) and significant in C2 (P = 0.037) and C3 (P = 0.012) but not C4 (P = 0.169); drift did not correlate with ownership, and path analysis suggested different mechanisms.
  • Defensive withdrawal movements to a falling virtual saw were greater during Saw Time than Control Time overall (combined P = 0.017), and hand movement dispersion was positively related to ownership and to feeling harmed.

Methods

  • Fifty participants were assigned to 5 between-groups conditions (n = 10 each): Incongruent (I) and Congruent C1–C4, where the virtual dominant arm was 1, 2, 3, or 4 times the real arm length; mean real arm length was 53 ± 3 cm, giving average C2/C3/C4 lengths of 106, 159, and 212 cm.
  • Participants wore a stereo head-mounted display and saw a first-person virtual body; all conditions had visuo-motor congruence, while visuo-tactile congruence was present in C1–C4 but not I. Elongation occurred over 2 minutes while participants touched a physical box.
  • Measures included a 7-item questionnaire (1–5 scale), proprioceptive drift via angle estimation before and after elongation for C2–C4, and hand-tracking dispersion before and during the virtual saw threat; analyses used nonparametric tests, ordered logistic regression, robust regression, and path analysis.

Limitations

  • The paper states that defensive movements were small because participants were instructed to remain motionless, creating competition between staying still and avoiding the saw; the data likely reflect motor initiation rather than full execution for some participants.
  • The paper states that in C4 the virtual hand was far from the body and visual precision/quality were poorer, and that spatial distance or limits on limb representation may contribute to the illusion decline; it also notes that richer multisensory stimulation may be needed for greater distortions.
  • Evident from the text: each condition had only 10 participants, drift was not measured in C1 or I, and path analysis treated ordinal questionnaire variables as interval-scale, which the paper acknowledges is not strictly justified.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1371/journal.pone.0040867

Cites

45 of 45 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 40 cited sources checked · 0 supported · 0 flagged

  • Findingnone given

    It is possible to quite dramatically alter body representation by inducing an ownership illusion over one very long arm in a situation where the entire body has been replaced by a virtual body seen from a first person perspective.

    “In this paper we show that it is possible to quite dramatically alter body representation, by inducing an ownership illusion over one very long arm in a situation where the entire body has been replaced by a virtual body seen from a first person perspective position (1PP).”
    Quote in the paperSubstantial claim
  • Findingown data

    There is no difference in the amount of hand movement between congruent and incongruent conditions.

    “Table 3 gives the means and standard errors for and from which it is clear that there is no difference in the amount of hand movement between congruent and incongruent conditions.”
    Quote in the paperNot a substantial claim
  • Findingown data

    Hand tracking dispersion during Saw Time was significantly greater than during Control Time for C1 and C2.

    “and is significantly greater for C1 and C2”
    Quote in the paperSubstantial claim
  • Findingown data

    Robust regression supports a negative relationship between virtual arm length and hand movement dispersion.

    “The regression fit is shown in Table 6, supporting the notion of a negative relationship between the virtual arm length and the hand movement dispersion.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [27] PW Holland, 1977, Robust regression using iteratively reweighted least-squares., Communications in Statistics-Theory and Methods source

      Not checked in the free run.

  • Findingown data

    Hand movement dispersion during Saw Time declines with elongation, taking into account dispersion during Control Time.

    “We now show that the dispersion in Saw Time declines with elongation, taking into account the dispersion during the Control Time.”
    Quote in the paperSubstantial claim
  • May combine two claims. 29
  • Classified as probably not a substantial claim. 17
  • The quote only partly states this claim. 2

  • May combine two claims.

    Findingown data

    Estimated probabilities of ownership score being at least 4 are 0.86, 0.78, 0.66 and 0.52 for elongations 1 through 4.

    “The estimated probabilities of the score being at least 4 are 0.86, 0.78, 0.66 and 0.52 respectively.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The median of the 30 angle estimates is 45.6°, and the median of the corresponding 30 standard errors is 0.76° with interquartile range 0.59°.

    “The median of these 30 angle estimates is 45.6°, and the median of the corresponding 30 standard errors is 0.76° with interquartile range 0.59°.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Q7 (the feeling of being harmed) shows a trend where the median is greater in the congruent condition.

    “The only other response that shows a trend is Q7 (the feeling of being harmed) where the median is greater in the congruent condition”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    For elongation 1 to 3 there are always at least 7 out of 10 participants with scores of at least 4; this declines to 4 out of 10 for elongation 4.

    “For elongation 1 to 3 there are always at least 7 out of 10 participants with scores of at least 4. This declines to 4 out of 10 for elongation 4.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Post-elongation measured hand angle (AngleAfter) was significantly greater than prior hand position angle (AngleBefore) for C2 and C3 but not for C4.

    “The (two-sided) significance levels are for C2 P = 0.037, for C3 P = 0.012, and for C4 P = 0.169.”
    • Also stated in: § The Effect of Elongation · plain
      “AngleAfter is significantly greater than AngleBefore for C2 (P = 0.04) and C3 (P = 0.01) but not for C4 (P = 0.17), Wilcoxon matched-pairs signed-rank tests.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    There is no difference in median scores for the ownership question Q3 between C1 and I, and the median scores are both high (4 out of 5).

    “However, there is no difference in median scores for the ownership question, and the median scores are both high (4 out of a maximum of 5).”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    The incorporation of a virtual arm up to three times the real length is accompanied by a defensive withdrawal movement evoked by a threat to the virtual arm near the distant hand position.

    “and a defensive withdrawal movement evoked by a threat to the virtual arm near the distant hand position.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Questionnaire scores and defensive withdrawal movements in response to a threat showed that the overall level of ownership was high in both C1 and I, and there was no significant difference between these conditions.

    “Questionnaire scores and defensive withdrawal movements in response to a threat showed that the overall level of ownership was high in both C1 and I, and there was no significant difference between these conditions.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The mean Saw Time dispersion is greater than the mean Control Time dispersion for each group I and C1 separately and for the two groups combined.

    “However, the mean Saw Time dispersion is greater than the mean Control Time dispersion for each group I and C1 separately (bearing in mind that the significance levels are two-tailed) and for the two groups combined.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Responses to Q1 and Q2 about touch referral were significantly different between conditions C1 and I, showing that participants perceived the mismatch between seen and felt touch in I.

    “However, responses to Q1 and Q2 about touch referral were significantly different between the two conditions C1 and I showing that the participants had perceived the mismatch between seen and felt touch in I.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Withdrawal movements were positively correlated with Q3 and Q7, validating the use of withdrawal movements to address ownership.

    “Regression analysis revealed that withdrawal movements were positively correlated with Q3 and Q7, validating the use of withdrawal movements to address ownership.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    All participants in the conditions with the long virtual arm perceived an elongation of the dominant virtual limb and not a distortion of visual space in the depth axis.

    “And indeed, all participants in the conditions with the long virtual arm perceived an elongation of the dominant virtual limb and not a distortion of visual space in the depth axis.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In a regression of hand movement dispersion on ownership and other variables, ownership had a positive slope (P = 0.0058) but no significant effects for the other two variables.

    “A regression of on , ownership and shows a positive slope for ownership (P = 0.0058) but no significant effects for the other two variables.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    A robust regression of hand movement dispersion on ownership and harmed resulted in a highly significant positive slope for both variables (P < 0.0005 in both cases).

    “However, a robust regression of on ownership and results in a highly significant positive slope for both variables (P<0.0005 in both cases).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Hand movement dispersion is positively related both to Q3 (ownership) and Q7 (harmed).

    “It is positively related both to Q3 (ownership) and Q7 (harmed).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Proprioceptive drifts and the difference in dispersion of movement data were significant in C2 and C3 but not in C4.

    “Additionally, proprioceptive drifts and the difference in the dispersion of movement data were significant in C2 and C3 but not in C4.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Dropping the two non-significant terms resulted in a significant positive slope for ownership (P < 0.01) but did not resolve the non-normality of the residual errors.

    “Dropping the two non-significant terms results in a significant positive slope for ownership (P<0.01), but does not resolve the problem of the non-normality of the residual errors.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Questionnaire scores for ownership were high in C2 and C3 and less in C4.

    “Questionnaire scores for ownership were high in condition C2 and C3 and less in C4.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    At virtual arm length equal to the real one, the fitted value of ownership is 4; at quadruple the size, the value is 3.3.

    “However, at virtual arm length equal to the real one the fitted value of ownership is 4 and at quadruple the size the value is 3.3.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    These sensations were reported in questionnaire results and observed through participants' motor defensive reactions in response to a threat towards the virtual hand.

    “These sensations were reported in questionnaire results and observed through participants’ motor defensive reactions in response to a threat towards the virtual hand.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    There is a positive linear regression slope of hand movement dispersion on harmed (P < 0.0001) with residual errors satisfying normality (Shapiro-Wilks P = 0.272).

    “The case of harmed is more straightforward – there is a positive linear regression slope of on harmed (P<0.0001) with the residual errors satisfying normality (Shapiro Wilks P = 0.272)”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    The same negative relationship was true for withdrawal movements and elongation.

    “The same was also true for withdrawal movements and elongation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    During the elongation phase, each image of the virtual arm was different from the previous one, inducing sensations of having an arm that continuously extended but still moved synchronously with the real one and received congruent and synchronous tactile feedback in relation to a box that would not be reachable in reality.

    “Here, during the elongation phase, each image of the virtual arm was different from the previous one inducing the sensations of having an arm that continuously extended but still moved synchronously with the real one and received congruent and synchronous tactile feedback in relation to a box that would not be reachable in reality.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing). May combine two claims.

    Premisecitation

    The artificial body part should obey various morphological, anatomical and postural constraints, including the necessity for human body part resemblance.

    “Furthermore, it has been proposed that the artificial body part should obey various morphological, anatomical and postural constraints (for a review see [6]) including the necessity for human body part resemblance.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [6] M Tsakiris, 2010, My body in the brain: a neurocognitive model of body-ownership., Neuropsychologia source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    It is possible to induce the illusion of having a very small or giant body using synchronous visuo-tactile stimulation on a visible dummy body seen from first person perspective and the unseen real body.

    “Moreover, a recent study showed that it is possible to induce the illusion of having a very small or giant body using synchronous visuo-tacile stimulation on the visible dummy body seen from first person perspective and the unseen real body [20].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [20] B van der Hoort, 2011, Being Barbie: the size of one’s own body determines the perceived size of the world., PLoS One source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Under the rubber hand illusion, participants asked to localize their real hand are more likely to point closer to the rubber hand after stimulation compared to before.

    “Under this illusory perception, participants when asked to localize their real hand they are more likely to point closer to the rubber hand after the stimulation compared to before [7], [9].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [7] M Botvinick, 1998, Rubber hands ‘feel’ touch that eyes see., Nature source

      Not checked in the free run.

    • cites [9] M Tsakiris, 2005, The rubber hand illusion revisited: visuotactile integration and self-attribution., J Exp Psychol Hum Percept Perform source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    In the rubber hand illusion, a fake hand 91 cm beyond the real one can induce the illusion, although with lesser intensity compared to a normal sized fake arm.

    “In [8] the RHI was induced using a fake hand 91 cm beyond the real one, although with a lesser intensity compared to when using a normal sized fake arm.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [8] KC Armel, 2003, Projecting sensations to external objects: evidence from skin conductance response., Proceedings of the Royal Society of London Series B-Biological Sciences source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Proprioceptive drift is widely considered as a behavioral correlate of the ownership illusion, although a recent study challenged the idea that there is a common underlying mechanism that connects drift with the subjective illusion of ownership.

    “The difference between the participants’ estimations before and after the stimulation is called ‘proprioceptive drift’ and it is widely considered as a behavioral correlate of the ownership illusion, although a recent study [10] challenged the idea that there is a common underlying mechanism that connects drift with the subjective illusion of ownership.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [10] M Rohde, 2011, The Rubber Hand Illusion: Feeling of Ownership and Proprioceptive Drift Do Not Go Hand in Hand., PLoS ONE source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisenone given

    The extent to which gross asymmetries in the fake body can be assimilated remains unknown.

    “However, the extent to which gross asymmetries in the fake body can be assimilated remains unknown.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [8] KC Armel, 2003, Projecting sensations to external objects: evidence from skin conductance response., Proceedings of the Royal Society of London Series B-Biological Sciences source

      Not checked in the free run.

    • cites [22] F Pavani, 2007, The role of hand size in the fake-hand illusion paradigm., Perception source

      Not checked in the free run.

    • cites [23] M Schaefer, 2007, Morphing the body: illusory feeling of an elongated arm affects somatosensory homunculus., Neuroimage source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    It is possible to generate an illusion of ownership of a rubber hand that was 3 cm larger than the real hand.

    “Additionally it has been shown that it is possible to generate an illusion of ownership of a rubber hand that was 3 cm larger than the real hand [22].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [22] F Pavani, 2007, The role of hand size in the fake-hand illusion paradigm., Perception source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Similar methods were used to give normal sized men the illusion of ownership over a very fat virtual body, seen from first person perspective and with synchronous visuo-tactile and visuo-motor stimulation.

    “Similar methods were used to give normal sized men the illusion of ownership over a very fat virtual body, again seen from a first person perspective and with synchronous visuo-tactile and visuo-motor stimulation [21].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [21] JM Normand, 2011, Multisensory stimulation can induce an illusion of larger belly size in immersive virtual reality., PLoS One source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Body ownership results from combining prior information (innate or gained from life experience) and current multisensory information.

    “It has been proposed that body ownership results from combining two types of knowledge: prior information that is innate or gained from the life experience (e.g. the appearance of our own body), and current multisensory information [6].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [6] M Tsakiris, 2010, My body in the brain: a neurocognitive model of body-ownership., Neuropsychologia source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Induction of ownership illusions generally requires multisensory stimulation with the same spatiotemporal pattern on the real and fake body part.

    “Generally the induction of ownership illusions requires multisensory stimulation with the same spatiotemporal pattern on the real and fake body part [7], [14].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [7] M Botvinick, 1998, Rubber hands ‘feel’ touch that eyes see., Nature source

      Not checked in the free run.

    • cites [14] M Costantini, 2007, The rubber hand illusion: Sensitivity and reference frame for body ownership., Consciousness and Cognition source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The illusion of having a very long nose can be produced without kinesthetic illusions when a finger of a blindfold subject is manipulated to tap the nose of another subject while the experimenter simultaneously taps the nose of the blindfold subject.

    “However, the illusion of having a very long nose can be produced without such kinesthetic illusions. This occurs when a finger of a blindfold subject (S0) is manipulated by the experimenter to tap the nose of another subject (S1) who is sitting in front facing away from S0 while the experimenter simultaneously taps the nose of S0 [19].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [19] VS Ramachandran, 1998, The perception of phantom limbs. The D. O. Hebb lecture., Brain 121 (Pt source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Simultaneous vibration on the biceps and triceps muscle tendons can induce the perception of a shrunken arm.

    “Also simultaneous vibration on the biceps and triceps muscle tendons can induce the perception of a shrunken arm [18].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [18] MR Longo, 2009, Contraction of body representation induced by proprioceptive conflict., Current Biology source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    The probability is high for ownership to be scored at the highest level for equal length, but still at triple length the probability remains high, and only shows a decline at quadruple length.

    “It is clear that the probability is high for ownership to be scored at the highest level for equal length, but still at triple length the probability remains high, and only shows a decline at quadruple length.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Just seeing an artificial limb 20 cm longer and connected to the body could result in topographic reorganization of the primary somatosensory cortex.

    “Furthermore, it has been found that just seeing an artificial limb 20 cm longer and connected to the body could result in topographic reorganization of the primary somatosensory cortex [23].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [23] M Schaefer, 2007, Morphing the body: illusory feeling of an elongated arm affects somatosensory homunculus., Neuroimage source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    Body representation is flexible and it is possible to feel ownership towards a transformed and very asymmetric body that contradicts all notions about the human body.

    “These findings revealed that the body representation is flexible and that it is possible to feel ownership towards a transformed and very asymmetric body that contradicts all the notions one has about the human body.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    The brain encodes personal space differently from peripersonal space, and also from far non-reachable extrapersonal space.

    “Secondly, neurophysiological studies on monkeys (for a review, see [34]) and behavioral studies in humans e.g. [35] have shown that the brain encodes personal space (i.e. the space occupied by our body) differently from the peripersonal space”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [34] M Graziano, 2002, How the brain represents the body: insights from neurophysiology and psychology; Hommel WPaB, editor: Oxford: Oxford University Press).

      Not checked in the free run.

    • cites [35] PW Halligan, 2003, Spatial cognition: evidence from visual neglect., Trends in Cognitive Sciences source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In study [8], the intensity of the RHI was smaller when a distant fake arm was used (+91 cm) compared to a normal size fake arm as indicated by questionnaire responses but not from skin conductance responses.

    “For example, in the study of [8] the intensity of the RHI was smaller when a distant fake arm was used (+91 cm) compared to a normal size fake arm as indicated by the questionnaire responses but not from skin conductance responses.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [8] KC Armel, 2003, Projecting sensations to external objects: evidence from skin conductance response., Proceedings of the Royal Society of London Series B-Biological Sciences source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Peripersonal space is thought to serve as a safety zone for the body, adapted to the body shape.

    “and is thought to serve as a safety zone for the body, adapted to the body shape [41].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [41] MS Graziano, 2006, Parieto-frontal interactions, personal space, and defensive behavior., Neuropsychologia source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    Proprioceptive drifts were affected by elongation but only through the sensation that the real arm feels longer and not through ownership.

    “Proprioceptive drifts were found to be affected by elongation but only through the sensation that the real arm feels longer and not through ownership.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Visual space was re-encoded in the virtual hand reference frames with a recalibration of the body segmental and postural configuration and a consequent update of the personal and peripersonal space under the perception of having a very long arm.

    “These findings imply that the visual space was re-encoded in the virtual hand reference frames with a recalibration of the body segmental and postural configuration and a consequent update of the personal and peripersonal space under the perception of having a very long arm.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Rapid changes in the primary somatosensory cortex (SI) due to visual exposure to a long artificial arm were found in study [23].

    “Rapid changes in the primary somatosensory cortex (SI) due to visual exposure to a long artificial arm were found in the study of [23]”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [23] M Schaefer, 2007, Morphing the body: illusory feeling of an elongated arm affects somatosensory homunculus., Neuroimage source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    This modulation was significantly and positively correlated with the magnitude of the subjects' sensations of having a long arm.

    “More interestingly, this modulation was significantly and positively correlated with the magnitude of the subjects’ sensations of having a long arm.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [23] M Schaefer, 2007, Morphing the body: illusory feeling of an elongated arm affects somatosensory homunculus., Neuroimage source

      Not checked in the free run.

45 of 45

  • The authors state this as an assumption.

    The angular drift is 0 at elongation 1 (when the arm is at the same length as the true arm there would be no angular displacement within random error).

    “Although we did not measure angular drift in condition C1 (no elongation but with congruence) we assume that the angular drift is 0 at elongation 1 - that is, when the arm is at the same length as the true arm there would be no angular displacement within random error.”

  • The authors state this as an assumption.

    The questionnaire variables can be treated as if they are on an interval scale for the path analysis.

    “For this purpose we treat all of the questionnaire variables as if on an interval scale.”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • The virtual hand illusion persists through radical transformations such as extensive elongation of the arm or change in the virtual hand position with respect to the real one.

    “This illusion persists through radical transformations such as extensive elongation of the arm [51] or change in the virtual hand position [52] with respect to the real one.”

    From Changing bodies changes minds: Owning another body affects social cognition (2015) · cites this paper as [51]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • C1 and C2 hand movements are called significant despite their reported P values

    Major

    The text calls the Saw Time increase significant for C1 and C2, but Table 5 reports two-tailed P values of 0.09 and 0.07. Neither meets the conventional 0.05 significance threshold; the paper elsewhere describes a P value of 0.0914 as a trend.

  • Discussion incorrectly claims significant C3 movement dispersion

    Major

    The discussion says the difference in movement dispersion was significant in C3, whereas Table 5 reports P = 0.72 for C3.

  • Reported fitted ownership at quadruple arm length does not match the path model

    Minor

    Table 7 gives an ownership intercept of 4.489 and an elongation coefficient of −0.341. At elongation 4, these yield 3.125, or about 3.1 to one decimal place, rather than 3.3.

    Reported 3.3 · recomputed 3.125

  • Path-analysis caption reverses the definition of angular drift

    Minor

    The results define AngleDiff as AngleAfter minus AngleBefore, but the Figure 8 caption defines anglediff in the opposite direction.

4 of 4

Cites

Flagged first, then by citations

1 of the 46 references couldn’t be matched to a known paper.

Research works printed but not linked: 1

  1. M Graziano, 2002, How the brain represents the body: insights from neurophysiology and psychology; Hommel WPaB, editor: Oxford: Oxford University Press).

Cited by

Sorted by citations

Related

Authors
Kilteni, K., Normand, J.-M., Sanchez-Vives, M. V., & Slater, M.
Affiliations
  • Universitat de Barcelona (ES)
  • Consorci Institut D'Investigacions Biomediques August Pi I Sunyer (ES)
  • Institució Catalana de Recerca i Estudis Avançats (ES)
Corresponding author
Slater, Mel
ORCID
Venue
PLoS ONE
Publisher
Public Library of Science (PLoS)
Published
2012-07-19
Volume
7
Issue
7
Pages
e40867
ISSN
1932-6203 (ISSN-L)
DOI
10.1371/journal.pone.0040867
PMC
PMC3400672
OpenAlex
W1965428772
Semantic Scholar
a6eb124caa6aafcd6bda8c6e524711b90aad993a
Cited by
499
References
46
Citations by year
2026: 26 · 2025: 41 · 2024: 43 · 2023: 32 · 2022: 47 · 2021: 51 · 2020: 64 · 2019: 35 · 2018: 37 · 2017: 31 · 2016: 26 · 2015: 25 · 2014: 26 · 2013: 15
FWCI
38.86
Type
journal article
Language
en
Open access
Licence
Locations
  • PLoS ONE (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • RECERCAT (Consorci de Serveis Universitaris de Catalunya) (publishedVersion, other-oa)
  • RePEc: Research Papers in Economics (submittedVersion)
  • Dipòsit Digital de la Universitat de Barcelona (Universitat de Barcelona) (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • UCL Discovery (University College London) (submittedVersion)
  • Figshare (submittedVersion, cc-by)
Funders
FP7 Ideas: European Research Council (227985)
Topics
  • Physical Sciences › Computer Science › Human-Computer Interaction › Virtual Reality Applications and Impacts
  • Social Sciences › Psychology › Experimental and Cognitive Psychology › Multisensory perception and integration
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Free Will and Agency
Keywords
body ownership, multisensory integration, proprioception, rubber hand illusion, body image, body size perception, immersive virtual reality

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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