Abstract
The present study is a follow-up of Elliott and Hansen (2010), which compared limb trajectory amendment measures. Because planning mechanisms can influence trajectory scaling and variability between trials, one major weakness of the measures contrasted in Elliott and Hansen (2010) is the use of many limb trajectories to obtain a measure of trajectory amendments (e.g., Heath et al., 2004; Khan et al., 2002). In contrast, a jerk-score can be obtained from a single trial (see Hogan & Flash, 1982). The present study contrasted jerk-score analyses (e.g., Goble et al., 2010) with other limb trajectory amendment measures. Fourteen participants performed reaches to 3 target amplitudes with (V) or without (NV) vision between movement onset and offset. Limb trajectories were monitored using motion tracking and a tri-axial accelerometer. As anticipated, participants exhibited more accurate and precise endpoint distributions in V than NV. Also, analyses using all measures of limb trajectory amendments did exhibit differences between V and NV trials. However, the interaction between the vision and target factors was only significant for the jerk and correlational measures, but not for the trajectory variability measures. Further, the largest partial eta square value for the vision by target interaction was obtained with the Fisher Z-score transformation of the correlational measures. The latter measure may be the most accessible and valid proxy for assessing limb trajectory amendments.Acknowledgments: This research was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Canada Foundation for Innovation (CFI) and the Ontario Research Fund (ORF).