The impact of image format and normative variables on episodic memory

Cognitive processes are complex and difficult to study because multiple variables can interact and confound the effect of the independent variable. To avoid this potential problem, experimental conditions are rigorously controlled and normative stimuli from standardized data-sets are preferably used. However, norms characterize the stimuli, but they do not prevent potential confounding effects. This is an important issue since many normative variables, such as familiarity and visual complexity, influence cognitive processes, such as memory. In Experiment 1, 20 participants completed an episodic memory task in order to see if name agreement, object agreement, familiarity, visual complexity, manipulability and colour diagnosticity of photos taken from the Bank of Standardized Stimuli (BOSS) influence memory performances. In Experiment 2, 20 participants completed a different episodic memory task to see whether memory performances were different for coloured photos, greyscale photos and black and white line drawings. Results showed that familiarity decreased memory accuracy whereas visual complexity increased it. Object agreement and colour diagnosticity brought a feeling of familiarity, and manipulability decreased the recognition of old objects. Results from the Experiment 2 showed that old photos were more recognized than old drawings and that new coloured photos were more correctly rejected than new greyscale photos and new drawings that had low colour diagnosticity. This study documents the different patterns of influences that normative variables exert on episodic memory and illustrates the importance of carefully controlling them in future studies. *Corresponding author: Mathieu B. Brodeur, Department of Psychiatry, Douglas Mental Health University Institute, McGill University, FBC Pavilion, 6875 Boul. LaSalle, Verdun, Québec, Canada H4H 1R3 E-mail: mathieu.brodeur@douglas. mcgill.ca Reviewing editor: Peter Walla, University of Newcastle, Australia Additional information is available at the end of the article