Coactivation of response initiation processes with redundant signals.

•Reaction time (RT) to multiple stimuli is faster than RT to a single stimulus.•An additive model of coactivation of initiation processes was investigated.•Predicted RT values of the coactivation model were equivalent to observed RT values.•Results indicated that initiation-related activation can summate to speed RT.•Coactivation of initiation processes can explain redundant signal effects.