  The idea of sensitivity in ant colony systems has been exploited in hybrid
ant-based models with promising results for many combinatorial optimization
problems. Heterogeneity is induced in the ant population by endowing individual
ants with a certain level of sensitivity to the pheromone trail. The variable
pheromone sensitivity within the same population of ants can potentially
intensify the search while in the same time inducing diversity for the
exploration of the environment. The performance of sensitive ant models is
investigated for solving the generalized vehicle routing problem. Numerical
results and comparisons are discussed and analysed with a focus on emphasizing
any particular aspects and potential benefits related to hybrid ant-based
models.
