Two studies of human contingency learning investigated the influence of stimulus salience on the cue competition effect of blocking. These studies demonstrated that blocking (defined as a difference in responding to blocked and control cues) was greater for target cues that had high “semantic salience” than those of lower salience. Moreover participants showed weaker responding to high salience blocked cues than low salience blocked cues, but a corresponding difference was not observed for control cues. These findings suggest that the influence of relative salience on associative learning depends on the relative validity of the cues in question. Use of eye tracking in Experiment 2 demonstrated that participants’ overt attention to cues was also influenced by both relative salience and relative validity. We describe three associative learning models, based on the attentional theory proposed by Mackintosh (1975), that are able to account for our key findings.