Failures to replicate blocking are surprising and informative - Reply to Soto

The blocking effect has inspired numerous associative learning theories and is widely cited in the literature. We recently reported a series of 15 experiments that failed to obtain a blocking effect in rodents. Based on those consistent failures, we claimed that there is a lack of insight into the boundary conditions for blocking. In his commentary, Soto (in press) argues that contemporary associative learning theory does provide a specific boundary condition for the occurrence of blocking, namely the use of same- versus different-modality stimuli. Given that in ten of our 15 experiments same-modality stimuli were used, he claims that our failure to observe a blocking effect is unsurprising. We cannot but disagree with that claim, because of theoretical, empirical, and statistical problems with his analysis. We also address two other possible reasons for a lack of blocking that are referred to in Soto's (in press) analysis, related to generalization and salience, and dissect the potential importance of both. While Soto's (in press) analyses raises a number of interesting points, we see more merit in an empirically guided analysis and call for empirical testing of boundary conditions on blocking.