Figure 1, Key Figure.

Schematic of “classical” and RSA-style approaches in cognitive control research. Design, A color-word Stroop task with four colors and four words. The participant is instructed to name the stimulus hue rather than read the written word. Analysis, top, The classical approach begins by defining abstract factor levels (here, congruent and incongruent) to which conditions (e.g., stimuli) are assigned. Within these levels, the outcome variables of interest (e.g., response time) are summed (Σ) then contrasted. Measures, top, These unidimensional measures are typically interpreted in terms of control processes (e.g., slower reaction time on incongruent relative to congruent trials indicates heightened control demands). Analysis, bottom, The RSA approach keeps the task conditions disaggregated (↔↕) in order to examine the set of pairwise similarities among measures (e.g., brain activity patterns) from all conditions — that is, their full similarity structure (grey and black lines). This observed similarity structure is then compared to structures predicted from theory. For example, a model of target representations would predict greater similarity between patterns from trials in which the target response was identical (i.e., between stimuli of same hue: e.g., black line connecting blue-hued “BLUE” and “GREEN” stimuli) versus different (e.g., between stimuli of same word in different hues: black line connecting red-hued and blue-hued “BLUE”s). The RSA approach thus provides indices reflecting the strength which multiple different representational schemes were encoded (e.g., the space defined by the light blue basis vectors, which correspond to potentially encoded variables). Theory, Typically, classical measures support inference (large orange arrow linking Measure to Theory) regarding control processes (entire CONTROL component of model, orange). Conversely, RSA-based measures can map more directly (large blue arrow linking Measures to Theory) onto theorized control representations (blue nodes within CONTROL component).