Does so-called interhemispheric transfer time depend on attention?

To our knowledge none of many past attempts to experimentally modulate the crossed-uncrossed differential (CUD) or so-called "interhemispheric transfer time" derived from appropriate visual reaction time experiments has ever succeeded. The present 4 experiments were designed to establish that (a) under normal attentional constraints, significant CUDs would be obtained, but that (b) lateral mobilization of attention by probabilistic (valid and invalid) cuing as to target location would significantly and systematically alter the CUDs. In a baseline experiment, a significant CUD was obtained. In Experiments 2-4, CUDs were rendered nonsignificant by probabilistic cuing. Specific experimental conditions generally did not significantly influence the CUD in a systematic direction. In only one of many analyses of those results did an experimental effect on the CUD reach significance: In Experiment 3 intrasubject mean reaction times yielded a significant complex dissociation of CUDs as a function of type of cuing (valid or invalid) and stimulus onset asynchrony. It was concluded that the CUD can be significantly modulated by target location cuing, but only under very specific conditions. The direction of the trends in all the experiments, and in the significant finding, suggests that the CUD component that is most markedly influenced by such cues is a postcallosal, motor component.