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SUMMARY:Noise and the two-thirds power law - Elon Portuglay\, MS Microsoft
DTSTART:20100913T090000Z
DTEND:20100913T100000Z
UID:TALK26189@talks.cam.ac.uk
CONTACT:Microsoft Research Cambridge Talks Admins
DESCRIPTION:The two-thirds power law\, an empirical law stating an inverse
  non-linear relationship between the tangential hand speed and the curvatu
 re of its trajectory during curved motion\, is widely acknowledged to be a
 n invariant of upper-limb movement. It has also been shown to exist in eye
 motion\, locomotion and was even demonstrated in motion perception and pre
 diction. This ubiquity has fostered various attempts to uncover the origin
 s of this empirical relationship. In these it was generally attributed eit
 her to smoothness in hand- or joint-space or to the result of mechanisms t
 hat damp noise inherent in the motor system to produce the smooth trajecto
 ries evident in healthy human motion. We show here that white Gaussian noi
 se also obeys this power-law. Analysis of signal and noise combinations sh
 ows that trajectories that were synthetically created not to comply with t
 he power-law are transformed to power-law compliant ones after combination
  with low levels of noise. Furthermore\, there exist colored noise types t
 hat drive non-power-law trajectories to power-law compliance and are not a
 ffected by smoothing. These results suggest caution when running experimen
 ts aimed at verifying the power-law or assuming its underlying existence w
 ithout proper analysis of the noise. Our results could also suggest that t
 he power-law might be derived not from smoothness or smoothness-inducing m
 echanisms operating on the noise inherent in our motor system but rather f
 rom the correlated noise which is inherent in this motor system. \n\n
LOCATION:Small public lecture room\, Microsoft Research Ltd\, 7 J J Thomso
 n Avenue (Off Madingley Road)\, Cambridge
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