title: Observation: Three reasons to avoid having half of the trials be congruent in a four-alternative forced-choice experiment on sequential modulation.
abstract: Sequential modulation is the finding that the sizes of several selective-attention phenomena--namely, the Simon, flanker, and Stroop effects--are larger following congruent trials than following incongruent trials. In order to rule out relatively uninteresting explanations of sequential modulation that are based on a variety of stimulus- and response-repetition confounds, a four-alternative forced choice task must be used, such that all trials with any kind of repetition can be omitted from the analysis. When a four-alternative task is used, the question arises as to whether to have the proportions of congruent and incongruent trials be set by chance (and, therefore, be 25% congruent and 75% incongruent) or to raise the proportion of congruent trials to 50%, so that it matches the proportion of incongruent trials. In this observation, it is argued that raising the proportion of congruent trials to 50% should not be done. For theoretical, practical, and empirical reasons, having half of the trials be congruent in a four-alternative task aimed at providing unambiguous evidence of sequential modulation should be avoided.
authors.affiliation: Department of Psychology, University of Iowa, Iowa City, IA, USA. jonathan-mordkoff@uiowa.edu
authors.forename: J Toby
authors.initials: JT
authors.lastname: Mordkoff
mesh_terms: D001288:Attention; D015986:Confounding Factors, Epidemiologic; D056344:Executive Function; D006801:Humans; D011930:Reaction Time; D012107:Research Design; D057190:Stroop Test