1. A method for detecting at least one similar behavioral phenomenon in two space-time video segments, the method comprising: for small space-time patches of pre-defined size around individual pixels of a corresponding pair of pixels across said two video segments, associating a local motion consistency measure between a pair of said space-time patches of said corresponding pair of pixels which determines whether or not said pair of patches could have resulted from the same underlying local motion without explicitly computing an underlying motion field; and from an aggregation of at least part of a plurality of said local motion consistency measures, determining the likelihood that said two space-time video segments could have resulted from the same underlying motion field, wherein said associating comprises calculating whether a vector ū with a non-zero temporal component exists which is perpendicular to space-time gradients of pixel values in said corresponding space-time patches without explicitly computing said vector ū.