  In this paper, we analyze a Hegselmann-Krause opinion formation model and a
Cucker-Smale flocking model with attractive-repulsive interaction. To be
precise, we investigate the situation in which the individuals involved in an
opinion formation or a flocking process attract each other in certain time
intervals and repeal each other in other ones. Under quite general assumptions,
we prove the convergence to consensus for the Hegselmann-Krause model and the
exhibition of asymptotic flocking for the Cucker-Smale model in presence of
positive-negative interaction. With some additional conditions, we are able to
improve the convergence to consensus for the solutions of the Hegselmann-Krause
model, namely we establish an exponential convergence to consensus result.
