It has been well documented that mental practice can improve performance on various cognitive and motor skills. However, the processes involved in mental practice and the theoretical explanations are less clear.
Rational of the study
According to Solso (1991), mental imagery refers to "a mental representation of a nonpresent object or event" (p. 267). Although this representation is not confined exclusively to the visual sense (e.g., one can "hear" a favorite tune or "feel" a favorite piece of sports equipment in one's imagination), it is usually associated in sport psychology with using "the mind's eye" (Porter & Foster, 1988).
In general, researchers (e.g. see Denis, 1989; Kosslyn, 1985) believe that mental images have two fundamental characteristics or dimensions: vividness and controllability. The vividness of an image denotes its clarity and "sharpness" or sensory richness (Richardson, 1988), whereas the term controllability refers to the ease and accuracy with which an image can be transformed or manipulated in one's mind (Kosslyn, 1990).
Literarture Review Analysis
Traditionally, measurement of imagery ability has involved assessment of either imagery vividness or of imagery controllability skills. The vividness dimension of visualization is generally measured through subjective, self-report tests. These tests usually require people to rate the clarity of images evoked by descriptive items (e.g. "the clapping of hands in applause") on 5- or 7-point Likert scales, although there appears to be no good reason for the counter-intuitive practice of assigning lower scores to greater vividness. In this regard, Mueller (1986) recommends that "responses indicating a positive attitude towards the attitudinal object . . . result in high scale scores" (p. 13).
By contrast, imagery control skills are usually measured by requiring people to complete objective tasks which elicit spatial visualization abilities. For example, they may be required to transform, in their minds, images of three-dimensional target shapes in order to decide whether or not they are congruent with given alternatives (Shepard & Metzler, 1971). Sometimes, however, the self-report paradigm has been used to assess image controllability, for example Richardson's (1969) modification of Gordon's (1949) test of imagery control.
Although these two properties of imagery are usually considered as separate dimensions, the theoretical basis of a conceptual distinction between them remains obscure. No researcher seems to have raised the obvious question of how an imaginary experience can be controllable if it is not vivid. The neglect of such issues highlights the need for greater conceptual rigor in imagery research.
The present study will examine two variables that contribute to the efficacy of mental practice--imagery perspective and task type. Subjects, who will natural internal or natural external imagers, mentally practiced a cognitive/visual task (an angles estimation task), and a motor/kinesthetic task (a stabilometer). Only the external imagers showed greater performance than the control on the motor/kinesthetic task, and only internal imagers showed greater improvement than the control group on the cognitive/visual task. Subjective reports of visual and kinesthetic imagery clarity also differed depending on the type of task being imaged.