Kinesthetic aftereffect and augmenting/reducing: a two-session procedure, and hence identification of stimulus-governed subjects, is contraindicated.

A few of the recent researchers of kinesthetic aftereffect (KAE) as an index of augmenting/reducing have continued to employ a two-session procedure. Findings that have accrued in the past decade indicate (a) The first administration of KAE is a reliable (internally consistent) and valid index of augmenting-reducing; (b) there are carry-over effects from the first to the second administration that bias the second session's preinduction scores; (c) KAE scores from sessions after the first do not relate to first-session scores (low retest reliability) and do not measure augmenting/reducing; and (d) unless special procedures are undertaken to avoid using the biased second- (or later-) session preinduction scores, a KAE procedure involving more than one session is contraindicated. When we reached a similar conclusion earlier (Baker et al., 1974), Petrie (1974) disagreed, arguing that a two-session procedure was needed to identify and eliminate an atypical subgroup, the "stimulus governed." The case for determining which subjects are stimulus-governed is assessed and found wanting. Except in special circumstances, a one-session KAE procedure, in which all preinduction trials precede the first exposure to aftereffect induction, is indicated.