Of course, the CUD is no longer an estimate of IHTT! In particular, if Dr is large enough in relation to Dl, then the CUD is negative!
Marzi's Meta-analysis Marzi, Bisiacchi, and Nico-letti (1991) carried out a meta-analysis of SRT studies and obtained the pattern shown in Figure 3. In addition to the standard significant rh x VF interaction, they found an overall LVF advantage and an overall Rh advantage. There was also an asymmetry in the crossed conditions, with selectively long RVF-Lh responses and no difference between the two uncrossed conditions. These results mean that [10v] > 0, [11v] < 0, [12v] < 0, and [13v] A 0. It follows from equations 10v— 13v that the meta-analysis is simultaneously consistent with all of the following three effects: (1) asymmetric transfer, (2) asymmetric hemispheric processing of the visual input, and (3) asymmetric hemispheric motor programming and response. In fact, assuming that CRrl < CRlr, the inequalities above yield PL < Pr and Vr < VL. But the meta-analysis is also consistent with symmetric transfer and asymmetric processing: CRlr = CRrl, Vr < VL and Pr > Pl. Thus, the meta-analysis does not imply asymmetry in relay.
For the second scenario, cognitive relay, we get similar results. Given the same inequalities observed in the metaanalysis, we find that if CRlr > CRrl, then OPl < OPr and IPr < IPl. Similarly, for motor relay, given the inequalities of the meta-analysis, we get that if CRlr > CRrl, then Ml < Mr and Pr < Pl.
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