Figure 2. Effects of changes in conditioning procedure on postural after-contraction movements.

One of the arms was always exposed to a ‘control type of conditioning procedure’ while the test arm was exposed either to the same type of procedure (trial A) or to a procedure which in one of the following specific ways differed from that in the control arm: omission of initial arm abduction movement (trial B), omission of forceful ‘hold-short’ abductor contraction (trial C), omission of post-contraction ‘hold-short’ relaxation period (trial D), and fast instead of slow return movement to intermediate position (trial E). For each type of trial, paired columns indicate mean ±s.d. (n= 10) of the ensuing non-volitional arm abductions in the control (C) and the test (T) arm, and the level of significance for the asymmetry is indicated.