Psychomotor decline can be described by discontinuities in response trajectories: comments on Vrtunski and Patterson...

Five methodological and experimental design concerns are identified in Vrtunski and Patterson's (1985) article. The discussed concerns involved: (a) the use of misleading premotor segment terminology, (b) the uncertain status of the repeated measures sphericity assumptions, (c) mean calculations across unequal trials of the four levels of stimulus conditions, (d) improper selection of a main effect for post hoc analysis and discussion of these results when a significant interaction was present, and (e) conflicting text and table values. These concerns have prompted us to question their psychomotor decline conclusions. And unless Vrtunski and Patterson can convince us that these concerns are unjustified, we have no choice but to doubt seriously the validity of their conclusions.