Select, then decide: Further evidence for separable selection and decision processes in short-term visual recognition

Recently, researchers have used evidence-accumulation models to analyse how performance in visual working memory (WM) tasks depends on both decision-making and non-decisional processes. One resulting claim is that selection of representations into the focus of attention and decision-making about those representations are separable processes, that this selection is facilitated by informative retro-cues, and that this process is evident in non-decision time when data are fit with a diffusion model. I attempted to address an alternative account of retro-cue effects on non-decision time: that they result from reduced uncertainty about non-memorial aspects of the task. In two 2AFC recognition experiments with retro-cues, participants had to choose between two probes–whose similarity to one another varied across conditions–to indicate which matched an item presented at a specified location in a sequentially-presented visual memory array. Crucially, the task minimized differences in uncertainty between the cue and no-cue conditions. Modelling showed a robust retro-cue effect in non-decision time, consistent with the advanced selection account of the retro-cue effect. Additionally, there were serial position and similarity effects, mostly evident on drift rate. These results support the contention that selection into the focus of attention is a separate process which facilitates stimulus use in decision-making.