This is an excerpt from Attention and Motor Skill Learning by Gabriele Wulf.
The effects of concurrent feedback described in this section are reminiscent of some interesting results that Franz Mechsner, a former colleague of mine at the Max Planck Institute for Psychological Research in Munich, Germany, obtained in his studies on bimanual coordination (e.g., Mechsner, 2004; Mechsner et al., 2001). Mechsner's studies followed up on the well-known phenomenon that in-phase movements (e.g., those in which the two hands move in mirror symmetry) are easier to produce, especially at high frequencies, than anti-phase movements (e.g., those in which the two hands move in parallel). You can easily experience this, for example, by oscillating your index fingers in parallel. When you increase the speed of the oscillations, you will probably find that your fingers end up moving in symmetry. What Mechsner tried to show is that the preferred in-phase pattern, rather than being “hardwired,” was based on the “perceptual goal” of the movement.
The way Mechsner tried to provide evidence for this idea was rather ingenious. He used a Playmobile kit (who said that scientists don't like to play?) and built an apparatus consisting of two flags that were attached to two handles via cranks. Participants, sitting at a table, moved the handles (which were positioned under the table surface so that they couldn't be seen) in circles and observed the circle movements of the flags on top of the table. In one condition, Mechsner turned one of the flags by 180°, so that an in-phase movement pattern of the hands would produce an anti-phase pattern of the flags, and vice versa. The interesting result was that, when participants started out with an anti-phase circle pattern of the flags (produced by an in-phase pattern of the hands) and then increased the speed, they tended to switch into a in-phase pattern of the flags (i.e., an anti-phase pattern of the hands)! Thus, the switch in the hand movement pattern was opposite to what is normally observed. Mechsner interpreted this and other related findings as evidence that actions are governed by “perceptual goals” (in this case, the perception of the flags), and that “the corresponding motor activity . . . is spontaneously and flexibly tuned in” (Mechsner et al., 2001, p. 69).
Mechsner's findings are somewhat different from those relating to the effects of external versus internal foci of attention in that performance of his task is dependent on the availability of feedback from the flags. When the flags are removed, participants are typically not able to produce the complex movement patterns they were able to produce with the flags. Yet his findings are also similar to those relating to attentional focus effects; both sets of findings show that focusing on the (perceptual) goal, or movement effect, allows the motor system to “spontaneously” produce effective movements. In fact, Mechsner and colleagues also noted, on the basis of their observations, “Anecdotal evidence seems to suggest that attention to the hands disrupts control of iso-frequency of the flags” (Mechsner et al., 2001, p. 72).