The serial-parallel dilemma: a case study in a linkage of theory and method.

The question as to whether humans perceive, remember, or cognize psychological items simultaneously (i.e., in parallel) or sequentially (i.e., serially) has been of interest to philosophers and psychologists since at least the 19th century. The advent of the information-processing approach to cognition in the 1960s reopened the inquiry, initiating a flood of experiments and models in the literature. Surprisingly for so elemental an issue, persuasive experimental tests have, until recently, proven rather elusive. Several decades of theoretical, methodological, and experimental effort, propelled and shaped by a meta-theoretical perspective, are leading to powerful strategies for assessing this and related cognitive issues. The present article reviews the theoretical and empirical history of these inquiries and details situations in which decisive experimental tests are possible.