Food (F) and magazine light (ML) refer to food plus magazine light and magazine-light-only presentations, respectively: Thus, in Condition 2, for example, we arranged 10 food deliveries and two magazine-light deliveries per component (10 F + 2 ML). The data used were numbers of responses between food presentations averaged across the 6 pigeons in Conditions 1 to 5. The lower-right graph shows mean sensitivity and bias values across Conditions 1 to 5, and mean values for each condition, for comparison purposes.