I came across "Magnetic sand": Illusions of interactivity, a May paper in Journal of Vision that catalogs a new variety of visual perception issue, in which the participant perceives an actually inert system is responding to them, which struck me as interesting in relation to some UAP sightings, particularly those where observers think lights in the sky are reacting to them. If nothing else it highlights how things can differ between what is actually happening and what an observer perceives is happening.
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We discovered a series of new illusions in which hand or finger movements near a random white noise display lead to the perception that the display is interactively altered contingent upon the observer's actions.
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In all demonstrations, the observer is expected to hold their finger(s) or palm very close to the dynamic random noise display, but not touch it. They should then execute the following movements, each of which leads to a visual illusion. All these illusions make the visual noise appear interactive with the finger movements. [emphasis added]
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Eight participants (7 male, 1 female), all students or researchers affiliated with the California Institute of Technology, took part in the study. All participants reported normal or corrected-to-normal vision and provided written informed consent prior to their involvement. They were compensated $50.00 for their participation in a 120-minute session, which included a short break after approximately 50 minutes. In addition to these laboratory participants, all reported effects were tested, refined, and confirmed through demonstrations—both onsite and via the project website—with 50 to 70 audience members each year at the Demo Night, held at the Vision Science Society Annual Meetings in 2019, 2022, 2023, 2024, and 2025. All participants were explicitly instructed to ensure clear perception of each illusion, from illusion 1 to illusion 4.
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New illusions. (a) Illusion 1. Iconic trace of trajectory. When the observer draws an "S" letter (or any other letter/pattern) on the dynamic noise display, they see a trace that fades away quickly. (b) Illusion 2. Magnetic repulsion/attraction. Open a palm as it approaches the display, then close the fingers (as though grabbing) as you pull away from it, and repeat. The nearby dots are perceived as though magnetic, moving away while the palm opens and gets close, and being attracted to the fingers when they grab and move away from the display. (c) Illusion 3. Action capture (with visible hand). The palm should be wide open, held very close and parallel to the noise display, then slowly moved left and right (or up and down), within a very small spatial range (a slow shudder). It perceptually captures the nearby dots, as though they were being captured and coming together with the palm. (d) Illusion 4. Action capture (with invisible hand). While observing the dynamic noise, the observer moves their hand up and down behind the display, so that the hand itself is invisible. The dynamic noise nearby (although often in the spreading area) may appear to be captured by the invisible hand.