Methods for Studying Human Laterality

Laterality research with normal subjects is plagued by contradictory findings, stemming from the diversity of methods used. These may include reaction time (RT) or accuracy measures with an imposed speed or accuracy set, go/no-go or target/nontarget discriminations, identity, similarity or category matches, and perceptual matching of simultaneously presented stimuli vs matching a test item to a memorized target (with various retention intervals, one, many, or constantly changing targets). The stimuli may be easy or impossible to verbalize; they may be treatable as unitary wholes or as collections of discrete features or elements. The task and stimuli may be familiar or novel, easy or difficult, practiced or unpracticed, and presented in isolation or accompanied by another easy or difficult, verbal or nonverbal, concurrent task. Even superficial changes in or interpretations of instructions, or differences in methods of presentation or subject populations may alter findings. The effects of sensory modality, the nature of the task, and the problems of measurement will be considered in this chapter.