(color online) (a) Normalized histogram of velocity measured by all displacements from the trajectories in each bin. The red lines are Gaussian fit of the data in each group. Trajectories are classified into five bins, – (black squares), – (red circles), and – (green up triangles), – (blue down triangles), and – (light blue rhombuses). (b) The plot for log( ) versus , with , where and σ are the fitting mean value and the standard deviation in the Gaussian fits in panel (a), respectively. (c) The standard deviation as a function of . The blue line is a linear fit of the data, , with and κ = 0.088.