Sensitivity. Eyeblink Sensitivity d' for the two groups in Sessions 1 and 2. d' was high in the conditioning session due to the presence of the US. In session 2, d' drops to a small value indicating no specificity for the key related to the target tone. In any part of the experiment, no sensitivity difference between the groups is observed. NB: The graph shows eyeblink sensitivity only. Twitches, however, display an equally low d' in both Sessions 1 and 2. Red: NM group; Yellow: PP group. Inset: Correlation of d' with the US-CS delay in Session 1. A positive correlation is present in the non-musician group (upper panel, r = 0.8, p < 0.05) but not in the musician group (lower panel, r = 0.4, p = n.s.). In Session 2 (not shown), no positive correlation is found in either group.