A novel visual illusion reveals different principles for perception and action D Huh |
|---|
Gatsby Computational Neuroscience Unit, University College London, United Kingdom
|
| The visual perception of biological motion has been suggested to have a tight coupling with the movement generation process. A well-known example is the speed illusion of single dot movements – the apparent fluctuation in the speed of a dot which is actually moving uniformly along a curved path. It has been suggested that the motion appears uniform only if it resembles the natural drawing motion of human subjects: For elliptic figures, this is known as the one-third power-law relationship between the speed and the radius of curvature (v(t) ~ r(t)^1/3) (Viviani and Stucchi 1992). However, the phenomenon has not been rigorously studied for non-elliptic movements. Our optimal-control based theory predicts a whole family of power-law relationships depending on the shape of the movement paths, instead of the fixed 1/3 power-law. Such generalized relationship was indeed confirmed in our movement and perception experiments – smaller exponent is observed for a path shape whose curvature oscillates with higher frequency. The data, however, revealed different ranges of exponents for two tasks. In the motor task, the exponent was found to range between 0 and 2/3, while it was between 0 and 1/2 in the perception task, which can be predicted from optimizing two different cost functions. Therefore, our result reveals two similar yet different principles for the perception and the action processes of curved motion. |
| Up Home |
|---|