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LIT-1275: What is embodiment? A psychometric approach

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StatusActive — read 2026-10-20 (NOTE-1004) in full, from the published article on the first author's lab site; worth reading as the first large-sample measurement of what the rubber hand illusion feels like, and as the study that split "embodiment" of a rubber hand into ownership, location and agency. 131 people rated 27 statements after 60 s of synchronous and of asynchronous brushing. A principal components analysis found four components in both conditions (embodiment of the rubber hand, loss of own hand, movement, affect) and a fifth, deafference, only after asynchronous brushing. Ownership and location rose above neutral only after synchrony, agency stayed below it, and ownership and location each predicted proprioceptive drift. Read it knowing that the three subcomponents come from a second varimax rotation of ten items dominated by one component, that there is no control for expectation or suggestion, and that every item is about a hand, none about the whole body.
Tagsself, psychometrics, embodied-cognition, neuroscience, consciousness, agency
Cited as “paper” byNOTE-1004 — Longo et al. — What is embodiment? A psychometric approach
Cited as “source” byTHEORY-766 — Brushing a seen rubber hand in synchrony with the hidden real hand, against asynchronous brushing, raises reports that touch is felt at the rubber hand and, more weakly and less reliably, that the rubber hand is one's own; the proprioceptive drift toward the rubber hand that accompanies these reports is not a measure of them; the standard comparison conditions do not equalise participants' expectations, so whether the stimulation or the expectation produces the report difference is open

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Longo, M. R., Schüür, F., Kammers, M. P. M., Tsakiris, M. & Haggard, P. (2008). What is embodiment? A psychometric approach. Cognition 107(3), 978–998. DOI 10.1016/j.cognition.2007.12.004.

Key takeaways

From the reading, NOTE-1004.

  • The illusion has structure. Across 131 people, ratings of 27 statements after 60 s of brushing fell into four components in both conditions: embodiment of the rubber hand (26.3% of variance after synchrony), loss of own hand, movement and affect. A fifth, deafference (pins and needles, numbness, a less vivid hand), appeared only after asynchronous brushing.
  • Embodiment splits three ways. A second analysis of the ten items loading on embodiment gave ownership, location and agency in both conditions. Ownership and location were positive after synchrony and negative after asynchrony. Agency, over a hand that never moved, was negative after both.
  • Ownership and drift go together. Felt hand position moved 1.34 cm toward the rubber hand after synchrony and a non-significant 0.30 cm after asynchrony (n = 120). Location (β = .485) and ownership (β = .425) each predicted the drift; agency did not.
  • The rubber hand displaces the real one. A “loss of own hand” component (paralysis, disappearance, loss of control) was higher after synchrony. The authors read this as a principle of “body constancy”: the new hand replaces the old one rather than being added to it.
  • The method is the claim. Structure that recurs across participants and conditions, and that predicts a behavioural measure, is offered as evidence that structured introspective report can measure a complex experience. No control separates that structure from expectation.

Standing in the record

Filed on 2026-10-20 at the owner’s request for experimental work building on the rubber hand illusion, alongside Lush 2020, Lush et al. 2020, Ehrsson et al. 2022 with Lush & Seth 2022, Roseboom & Lush 2022, Rohde, Di Luca & Ernst 2011, Abdulkarim & Ehrsson 2015 and Kalckert & Ehrsson 2012. Read in full: Active.

It is the first replication in the record with a large sample, named tests and drift measured in both conditions, so it bears on THEORY-765’s promotion test, though not on its suggestion control. It splits ownership from location within a hand, which is a part-level analogue of Blanke & Metzinger’s split between self-identification and self-location (THEORY-768); it measures nothing about the whole body. Its “loss of own hand” component is a questionnaire sign of the trade-off THEORY-769 predicts. It reports ownership without agency in the condition means and the two cohering across people, and the authors draw both conclusions; that bears on THEORY-458 without testing its comparator. It says nothing about interoception (THEORY-767). Its argument that covariance among reports reveals the structure of an experience is a case for QUESTION-048. Haggard is also the author of LIT-1009, whose agency is the narrow motor sense this paper’s agency items do not reach. The NOTE sets this out.

Filed alongside, earlier in the batch: Botvinick & Cohen 1998 (LIT-1277), Lenggenhager et al. 2007 (LIT-1279), Blanke & Metzinger 2009 (LIT-1274), Apps & Tsakiris 2014 (LIT-1262), Seth 2013 (LIT-1263).

One of the sources of THEORY-766 (filed 2026-10-20), which restates the rubber hand synchrony effect as a difference in reports, separates drift from those reports, and leaves open whether expectation produces the difference.

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