 The mechanism mediating this direct binding has not been clarified but several hypotheses have been put forward.One theory explains it as a race between automatic activation of a previous stimulus-response route and the reengagement of the "algorithmic" route and another theory suggests the operation of an "action-trigger" where repeated stimuli trigger the previous response through perceptual or conceptual associations with the original stimulus.In support of this theory is evidence of a response congruency effect, which would be expected from these stimulus-response bindings.