  We study a minimal cognitive flocking model, which assumes that the moving
entities navigate using exclusively the available instantaneous visual
information. The model consists of active particles, with no memory, that
interact by a short-ranged, position-based, attractive force that acts inside a
vision cone (VC) and lack velocity-velocity alignment. We show that this active
system can exhibit -- due to the VC that breaks Newton's third law -- various
complex, large-scale, self-organized patterns. Depending on parameter values,
we observe the emergence of aggregates or milling-like patterns, the formation
of moving -- locally polar -- files with particles at the front of these
structures acting as effective leaders, and the self-organization of particles
into macroscopic nematic structures leading to long-ranged nematic order.
Combining simulations and non-linear field equations, we show that
position-based active models, as the one analyzed here, represent a new class
of active systems fundamentally different from other active systems, including
velocity-alignment-based flocking systems. The reported results are of prime
importance in the study, interpretation, and modeling of collective motion
patterns in living and non-living active systems.
