Experimenter Naivete and Imagery Practice

The effects of imagery practice on motor skill acquisition have been examined for over 50 years (Sackett, 1935) under many labels. Mental practice (Corbin, 1967), mental rehearsal (Y amamoto & Inomata, 1982), mental training (Ulich, 1967), and visuo-motor behavior rehearsal (Noel, 1980) have all been employed to describe basically the same process. Equally varied have been the motor tasks utilized in research. Familiar motor tasks such as the basketball free throw (Eideness, 1965), volleyball serve (Shick, 1970) and tennis forehand (Surburg, 1968), as well as novel tasks such as target tracking (Kohl & Roenker, 1983), have been incorporated into imagery research. Intons-Peterson (1983) conducted a series of studies involving imaginal or perceived judgments to determine if imagery paradigms are influenced by experimenter expectation. The results of these studies, as well as those of earlier work (Intons-Peterson & White, 1981), substantiated the hypothesis that an experimenter knowledgeable of the paradigm could introduce unconscious bias into an imagery study. Tacit cues such as voice inflections, meaningful pauses, and certain verbal and nonverbal feedback (i.e., demand characteristics) can be given by the experimenter. The results of these studies raise questions regarding the findings of imagery research involving motor tasks. First, has imagerylmotor skill research been conducted in such a manner that bias of this type may have been introduced? Second, are imageryfmotor skill studies as sensitive to these biases as were the perceived judgments of Intons-Peterson's (1983) research? A perusal of imagerylmotor skill research revealed the utilization of various instructional conditions and practice sessions. For example, taped instructions were provided by Harris and Robinson (1986), task information and demonstrations were provided by Ryan and Simons (1982), and written instructions were used by Epstein (1980). Some of these procedures were apparently done with experienced researchers and with a protocol that could have introduced an unconscious bias. Intons-Peterson (1983) concluded that naive experimenters were required when conducting experiments involving imaginal or perceived judgments (i.e., single-blind protocols). Rosenthal(1966) identified a similar effect pertaining to experimenter expectancy. Martens (1970), however, concluded that experi-