L4- Human locomotion Flashcards
What is optic flow?
The apparent motion of the world at the back of the eye
-Retinal flow- info actually available to the brain
What is retinal direction?
Using visual markers to line up with a target
(e.g. rear view mirror)
What is gaze direction? (steering strategy)
Turning until head lines up with the body (closing angle)
What are the 4 potential sources of steering information?
Retinal flow (RF)
Retinal direction (RD)
Gaze direction (GD)
Body rotation (BR)
How can retinal flow, gaze direction, retinal direction, and body rotation be biased?
Retinal flow- rotate ground plane around steering and fixation target.
Gaze direction- Translate (drift) the viewport in which the scene is viewed
Retinal direction- Introduce explicit source of retinal direction info (car badge) and drift left/right.
Body rotation- physically rotate ppts
Outline Wilkie & Wann’s (2005) studies
1)
-Biased GD and/or RF
-Both used for steering. Additive accumulation of errors when both biased in same direction
2)
-Also biased RD
-steer using RF and RD
-Greatest oversteer when both positively biased
3)
-Biased BR
-Had little impact when veridical GD and RF present
SUMMARY:
-RF, RD, & GD all contribute in an additive manner
Describe Wilkie & Wann’s (2002) varying info quality study
Degraded Flow (retinal and direction)
-Biased RF- more error in daylight than dark (using RF more) - use gaze direction more in dark
-Biased RF; unbiased RD- same results with smaller magnitude (veridical RD info reduced error)
-degraded flow increases reliance on other sources
-Biased RD; unbiased RF- more error as darkness increases (more reliance on RF, but info degraded)
-Human locomotion needs to reflect the flexible combination of information sources to allow for robust control.
How can we model rotation rate in human steering?
a = Brf + Brd + Bgd
a- rotation rate
B= weighting for each information source (add up to 1)
How can we model human steering?
Alpha dot model
.. . .
θ = ka - bθ
