Exp Brain Res (2011) 209:19–27 Fig. 2 Group masking curves. Upper graph the average performance accuracy across participants is shown in blue. SOAs (time between visual stimulus onset and TMS pulse onset) are on the horizontal axis, proportion correct is on the vertical axis. Red curves shading the per- formance curve represent the standard error of the mean. Open circles reXect a signiWcant decrease from the all-round mean performance. Lower graph the average visibility rating across participants is shown in blue. SOAs are on the horizontal axis, visibility rating between 1 and 4 is on the vertical axis. 2.5 marks the border between ‘seen’ and ‘not seen’. Red curves again reXect standard error of the mean. Open circles reXect a signiWcant decrease from the all-round mean visibility rating diVerent scenario. Orientation discrimination accuracy was decreased in 70 ms, 90 ms, and seemingly in 110 ms, in what seem to be three separate dips in performance. In between these SOAs, at 80 ms and at 100 ms, there seemed to be no masking eVect—not a slight decrease of eVect, but a real return to baseline. Statistically, the earlier two of these three dips are conWrmed to be signiWcant. As explained in the Methods section, we conservatively compared masking eVects in individual time windows with the all-round mean. Table 1 reveals the resulting t and P values for these com- parisons. Since this was an exploratory study, the number of comparisons was too large to statistically correct for (as dis- cussed in the Methods section). Therefore, results are tenta- tive and future research should aim to replicate and conWrm these Wndings in hypothesis-driven experiments. For the moment, in our comparison to all-round mean, our data sug- Table 1 All statistical values from comparison to all-round mean Objective performance Visibility rating 0 ms 10 ms 20 ms 30 ms 40 ms 50 ms 60 ms 70 ms 80 ms 90 ms 100 ms 110 ms 120 ms 130 ms 140 ms 150 ms t value ¡1.798 1.080 0.630 ¡0.796 0.528 0.383 0.595 ¡2.406 1.170 ¡1.930 1.116 ¡1.114 1.804 1.459 ¡0.234 ¡0.110 P value 0.053 0.154 0.272 0.223 0.305 0.355 0.283 0.020 0.136 0.043 0.147 0.147 0.052 0.089 0.410 0.458 t value ¡0.148 0.180 ¡0.300 0.194 0.401 0.998 0.759 ¡0.193 ¡0.601 ¡0.484 0.451 0.313 ¡3.230 0.121 ¡1.839 ¡0.227 23 P value 0.443 0.431 0.386 0.425 0.349 0.172 0.234 0.425 0.281 0.320 0.331 0.381 0.005 0.453 0.050 0.413 Bold values are statistically signiWcant gest that there was a behavioral impairment at 70 ms (t(9) = 2.41; P < 0.05) and at 90 ms (t(9) = 1.93; P < 0.05). Note that time window 0 ms closely approached signiW- cance, with (t(9) = 1.80; P = 0.053). In light of previous research (Laycock et al. 2007), this very early dip might also reXect behaviorally relevant processing. If diVerent participants have individual masking curves around 100 ms, but slightly displaced temporally, a group masking curve with separate dips could result artifactually from the averaging of these individual curves. To rule out this option, we looked into the individual masking curves. Individual curves were noisier than the group curve, which is to be expected with a total of 15 trials per time window per subject, on which a single accuracy ratio is based. In spite of this, we noticed that many individual participants showed at least two of the three dips (decreases in perfor- mance at SOA 70, 90, or 110 compared to the SOAs imme- diately before and after). To allow inspection of these ‘dips’, we provide all ten individual masking curves (focused on the time windows of interest) in Fig. 3. These include curves of participants in whom masking seemed wholly unsuccessful, but were nonetheless included to be conservative (see “Methods”). With 15 trials per time win- dow, and taking interindividual diVerences into account, these results seem remarkably consistent. For instance, one of the two participants without any ‘dips’ at the appointed time windows showed two dips at 60 and 80 ms, rather than 70 and 90 ms. Such variability is to be expected, which is why a group curve remains most informative. The individ- ual curves shown in Fig. 3 at any rate do not suggest that 123