In three human causal learning experiments, we examined attentional modulation in the blocking task, in which participants typically learn little about a novel cue B when it is paired with a previously trained, predictive cue A. Evidence indicates that this blocking training led to a decrement in attention to the blocked cue B. The present experiments addressed whether this decrease in attention to the blocked cue could be better explained as being due to lateral inhibition from the pretrained cue A to the blocked cue B, or as a cue-specific property that is not conditional on the presence or absence of other stimuli. Strong effects of learned predictiveness were observed on participants' causal judgments (Experiment 1) and choice behavior (Experiments 2 and 3). However, no evidence for lateral inhibitory processes emerged in any of the experiments, despite explicit attempts to maximize experimental sensitivity to this effect. The results are discussed in the context of formal models of the operation of attentional processes in human and animal learning.