  We discuss the collective dynamics of self-propelled particles with selective
attraction and repulsion interactions. Each particle, or individual, may
respond differently to its neighbors depending on the sign of their relative
velocity. Thus, it is able to distinguish approaching (coming closer) and
moving away individuals. This differentiation of the social response is
motivated by the response to looming visual stimuli and may be seen as a
generalization of the previously proposed, biologically motivated, escape and
pursuit interactions. The model can account for different types of behavior
such as pure attraction, pure repulsion, or escape and pursuit depending on the
values (signs) of the different response strengths, and provides, in the light
of recent experimental results, an interesting alternative to previously
proposed models of collective motion with an explicit velocity-alignment
interaction. We show the onset of large scale collective motion in a subregion
of the parameter space, which corresponds to an effective escape and/or pursuit
response. Furthermore, we discuss the observed spatial patterns and show how
kinetic description of the dynamics can be derived from the individual based
model.
