The aim of this study is to test a new technique that allows comparisons to be made between movement measures of between-trail (perceptual) and within-trail (movement) variability within the same perception-action task and person.
Three groups of 8 students took part. At first participants produced 0° with three practice trails (0:0, 0:180 and 0:90). For the next three trials the cross-modal phase relation was set to 0° (0:0). This was followed by a block of six trials with the crossmodal phase relation set to 90° (0:90). The next six trials set the crossmodal relation to 180° (0:180), followed by three more 0:0 trials. Finally, there were two blocks of four trials in which the instructions were to produce either 180° or 90° visually.
First, they analyzed the MVLW data from the consistent conditions. Pairwise comparisons indicated the main effect of phase condition was due to within-trial stability at 0:0 being higher than the other two conditions, the main effect of frequency was due to stability being higher at 1 Hz. An average 90:90 and 180:180 were not different from each other.
Second, they analyzed the MVLW data from the 0° visual target conditions. Pairwise comparisons showed that the main effect of phase condition was due to within-trial stability at 0:0 being higher than the other two conditions and 0:90 being more stable than 0:180.
A clear relationship existed between within- and between trial stability. The matching scale of the two measures is evidence supporting the hypothesis that the differential movement stability is being caused by the differential perceptual stability.
The main new result is that the 0° visual target stabilized movements that were at a non-0° phase relationship to the dot being tracked.
The five conditions from experiment 1 where replicated plus two new conditions – 90:0 and 180:0. Pairwise comparisons showed that the 0° visual target conditions were more stable than the non-0° visual target conditions. An ANOVA on the non-0° visual target conditions revealed they did not differ in their stability.