CFS-crafter: An open-source tool for creating and analyzing images for continuous flash suppression experiments

Continuous flash suppression (CFS) is a popular masking technique used to manipulate visual awareness. By presenting a rapidly changing stimulus to one eye (the 'mask'), a static image viewed by the other (the 'target') may remain invisible for many seconds. This effectiveness affords a means to assess unconscious visual processing, leading to the widespread use of CFS in several basic and clinical sciences. However, the lack of principled stimulus selection has impeded generalization of conclusions across studies, as the strength of interocular suppression is dependent on the spatiotemporal properties of the CFS mask and target. To address this, we created CFS-crafter, a point-and-click, open-source tool for creating carefully controlled CFS stimuli. The CFS-crafter provides a streamlined workflow to create, modify, and analyze mask and target stimuli, requiring only a rudimentary understanding of image processing that is well supported by help files in the application. Users can create CFS masks ranging from classic Mondrian patterns to those comprising objects or faces, or they can create, upload, and analyze their own images. Mask and target images can be custom-designed using image-processing operations performed in the frequency domain, including phase-scrambling and spatial/temporal/orientation filtering. By providing the means for the customization and analysis of CFS stimuli, the CFS-crafter offers controlled creation, analysis, and cross-study comparison. Thus, the CFS-crafter-with its easy-to-use image processing functionality-should facilitate the creation of visual conditions that allow a principled assessment of hypotheses about visual processing outside of awareness.