How participants perceive the position of their own hand in various contexts will be examined. This will include changing the visual display to suggest the hand is in a slightly different position, and asking participants to indicate where they think it is by pointing with their other hand.
Hand position can be estimated visually, from an image on the retina, and proprioceptively, from sensors in the joints, muscles, and skin. The brain is thought to weight and combine available sensory estimates to form an integrated multisensory estimate. Inherent in this process is the capacity to realign one or both sensory estimates when they become spatially mismatched, as when washing dishes with the hands immersed in water, which refracts light. It is generally assumed that if a person knows about the sensory mismatch somehow, the realignment will not occur. This assumption will be tested in two experiments by giving people this information in different ways. Expt. A: Conscious awareness of the mismatch will be presented in different ways, or absent. Expt. B: Movement error feedback will be presented in different ways, or absent.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
Enrollment
300
Participant is told there will be a mismatch between their target finger and the visual indicator of target finger position. They will be shown a diagram explaining this.
Foamboard under mirror removed, making the mirror see-through and the hand directly visible. Mismatch between target hand and visual indicator will be directly visible.
After the participant points at each target, a cursor indicating final pointing position will be displayed briefly. The visual indicator of the target hand will be displaced.
Hannah Block
Bloomington, Indiana, United States
RECRUITINGRealignment
Measured by comparing where the subject points on a touchscreen when indicating perceived position of visual and proprioceptive targets early vs. late in the behavioral task.
Time frame: 1 day
Visuo-proprioceptive weighting
The degree to which participant relies on vision vs. proprioception when both are available. Measured by comparing where the subject points on a touchscreen when indicating perceived position of visual vs. proprioceptive targets.
Time frame: 1 day
Target estimation variance
Variance with which participant estimate visual and proprioceptive target positions. Computed from where subjects point at targets on a touchscreen.
Time frame: 1 day.
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After the participant points at each target, a cursor indicating final pointing position will be displayed briefly. The visual indicator of the target hand will not change, but the cursor indicating pointing hand position will change.
The visual indicator of the target hand will be displaced, but there will be no cursor to indicate the pointing hand's position.
Participants will not be told anything about the visuo-proprioceptive mismatch. Instead, they will be asked simply to attend to the target positions.