Retention of relative force in the scaling of a serial force pattern with an attenuated-force tap

The present study was designed to examine the retention of relative force i n the scaling of a serial terce pattern in a finger-tapping sequence using an attenuated tap. On practice trials, 12 undergraduate students tapped a f orce plate connected to strain gauges that gave them feedback about the for ce. On test trials, participants recalled the force pattern (200 gm-200 gm- 200 gm-100 am) and the intertap interval (400 msec.) practiced during the p ractice period without the feedback (recalled task). Then, they adaptively produced a halved (halved task) or doubled force profile (doubled task) at the fixed intertap interval. Analyses showed that mean peak forces at the f irst three tap positions of the tapping sequence undershot the expected acr oss all tasks. Hence, the ratios of the forces in Serial Positions 1:4, 2:4 , and 3:4 were considerably lower than 2.0. This is a contextual effect sug gesting that the last attenuated tap affected the first three taps of the t apping sequence. Thus, because the relative force of movements appears to b e a weaker invariant feature than sequencing and relative timing for genera lized motor program theory of Schmidt and Lee, this finding does not suppor t the relative force for a generalized motor program..