Disequilibrium as an Alternative to Internal States and Affordance.
A five-minute VR body-swap reliably bends size and distance judgments in adults, so check for this bias before any perception-based ABA task.
01Research in Context
What this study did
Valeri et al. (2017) used virtual reality to trick adults into feeling they had a child-sized or giant-sized body. They then asked the adults to judge how big or how far away real objects were. The team ran the same setup ten times to see if the illusion held.
All participants had typical vision and no diagnosis. The VR headset swapped the person’s real hands and feet for smaller or larger virtual ones. After a short walk, the experimenter held up a foam block and asked, “How big is this?”
What they found
When people felt they had a tiny body, the foam block looked huge and far away. When they felt huge, the same block looked tiny and close. The shift happened every time, across all ten tests.
No one reported feeling dizzy or fooled once the headset came off. The size-distance illusion vanished as soon as the virtual body matched their real body again.
How this fits with other research
Dowdy et al. (2019) took the same “disequilibrium” idea and gave it legs. They used a free online calculator to predict how long a teen with autism would stay in his seat. The math worked; the boy completed the whole predicted span. Where Valeri only theorized, Dowdy showed the model can set real work periods you can bank on.
Mittal et al. (2024) pooled six VR studies with autistic youth and found large gains in social-emotional skills. Their meta-analysis includes body-swap illusions like Valeri’s, but targets social learning, not object size. Together the papers say: tweak the felt body, and you can tweak either perception or social responding.
Mitchell et al. (2007) also used VR, but to teach seating rules in a café. Both labs use headsets to bend perception, yet Peter cares where kids sit, Valeri cares how big things look. Same tool, different levers.
Why it matters
If you run tasks that rely on size or distance judgments—matching picture cards, reaching for items, safety drills—know that a client’s body-size illusion can skew their answers. Run a quick VR calibration first: show a standard object after the headset body and ask, “How big?” If the answer is off, you have a measurable bias you can correct for before teaching new skills.
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Join Free →Hold up a standard 10 cm block after any VR warmup and ask the client to estimate its size; note any over- or under-estimation and adjust teaching materials accordingly.
02At a glance
03Original abstract
A classical question in philosophy and psychology is if the sense of one's body influences how one visually perceives the world. Several theoreticians have suggested that our own body serves as a fundamental reference in visual perception of sizes and distances, although compelling experimental evidence for this hypothesis is lacking. In contrast, modern textbooks typically explain the perception of object size and distance by the combination of information from different visual cues. Here, we describe full body illusions in which subjects experience the ownership of a doll's body (80 cm or 30 cm) and a giant's body (400 cm) and use these as tools to demonstrate that the size of one's sensed own body directly influences the perception of object size and distance. These effects were quantified in ten separate experiments with complementary verbal, questionnaire, manual, walking, and physiological measures. When participants experienced the tiny body as their own, they perceived objects to be larger and farther away, and when they experienced the large-body illusion, they perceived objects to be smaller and nearer. Importantly, despite identical retinal input, this "body size effect" was greater when the participants experienced a sense of ownership of the artificial bodies compared to a control condition in which ownership was disrupted. These findings are fundamentally important as they suggest a causal relationship between the representations of body space and external space. Thus, our own body size affects how we perceive the world.
The Behavior analyst, 2017 · doi:10.1371/journal.pone.0020195