There are several possible scenarios how the integration might take place. It might be that both verniers are
completely independently stored for longer periods of time and that their integration into one offset occurs only just before awareness is reached (
Figure 4A). Different dominance values might be reached because TMS selectively affects the first or the second vernier representation differently depending on the TMS onset asynchrony, thereby biasing perception towards the other, less-affected vernier. In this case, processing of the first vernier would be impaired with earlier TMS and processing of the second vernier would be impaired with later TMS, which would bias vernier offset perception towards the second or first vernier, respectively. However, such a scenario is unlikely because if we assume that the modulating effects of TMS are due to interference with completely independently stored verniers, we would expect that TMS also interferes with a single presented vernier, which is equivalent to a completely independently stored vernier. In
Experiment 3, we show that this is not the case even though the verniers were of considerably smaller offset sizes which are more prone to TMS interference (
Figure 3). The fact that TMS does not have an effect on an individual vernier is not surprising because the vernier was of high luminance (Weber contrast ∼1) and therefore too strong for TMS to interfere. Other studies that have found TMS masking effects have typically used much weaker stimuli (Amassian et al.,
1989; Corthout et al.,
1999; Jolij & Lamme,
2005; Kammer, Scharnowski, & Herzog,
2003; Kastner, Demmer, & Ziemann,
1998; Ro, Breitmeyer, Burton, Singhal, & Lane,
2003). The representation of the single vernier in
Experiment 3 is of course not directly comparable to the representations of the vernier stimuli in
Experiment 1 because in the latter case the two vernier representations interact. However, when assuming completely independent vernier representations in
Experiment 1, they are comparable to the individual verniers of
Experiment 3. Hence,
Experiments 1 and
3 show that TMS can interfere with the vernier representations only when they are interacting with each other (
Figure 4B).