Investigations of decision making have typically assumed stationarity, even though commonly observed “context effects ” are dynamic by definition. Mirror effects are an important class of context effects that can be explained by changes in participants ’ decision criteria. When easy and difficult conditions are blocked alternately and a mirror effect is observed, participants must repeatedly change their decision criteria. The authors investigated the time course of these criterion changes and observed the buildup of mirror effects on a trial-by-trial basis. The data are consistent with slow, systematic changes in decision criteria that lag behind stimulus changes. The length of this lag is considerable: analysis of a simple dynamic signal-detection model suggests participants take an average of around 14 trials to adjust to new decision environments. This trial-level measurement of experimentally induced changes has implications for traditional blockwise analyses of data and for models of decision making.

Relating behavioural deficits to lesion site has long been an important tool for localising the brain bases of cognitive function. Voxel-based methods, based on statistical analyses of structural brain images, allow a major step forward in the effectiveness of this approach. These methods provide a fine-grained assessment of damaged tissue by assigning a continuous value to each voxel over the entire brain. This information, correlated with continuous behavioural data reflecting specific aspects of cognition, offers new opportunities for identifying the neural organisation underlying cognitive function. The research reported here demonstrates the ability of this correlational methodology to differentiate between the neuro-cognitive components involved in word recognition and lexical decision, providing an important new tool for directly linking brain areas to specific aspects of psychological performance. © 2004 Elsevier Ltd. All rights reserved. Keywords: Neuro-cognitive component processes; Voxel-based correlational methodology; Lesion-deficit approach 1.