category (e.g., a bat, sharing both features with the correct category mammal and the incorrect category bird). Dale et al. (2007) hypothesized that for atypical exemplars, both response options would receive some degree of activation, whereas for the typical exemplars, activation would largely be limited to the correct category. Consequently, for atypical exemplars, the incorrect category should exert a stronger attraction, and mouse movements should deviate more in its direction even if participants finally choose the correct option. 2
Creating mouse-tracking experimentsIn this section we demonstrate how a mouse-tracking experiment can be created in OpenSesame (Mathôt et al., 2012). OpenSesame is a free, open-source software for creating experiments via a graphical user interface which additionally allows for full customization of studies using Python code. 3 To simplify the creation of mouse-tracking experiments inside this framework, we developed the mousetrap plugin for OpenSesame. Installation instructions and additional documentation for the plugin are available in its GitHub repository at https://github.com/pascalkieslich/mousetrap-os.
Creating an experimentThe first step is to start OpenSesame and create a new experiment by clicking on File/New and selecting the default template. Experiments in OpenSesame are assembled from a set of items, for example, a sketchpad item for presenting graphical content on the screen, a keyboard_response item for collecting key presses, and a logger item for writing data into log files. Figure 1 shows the OpenSesame interface with the item toolbar on the left-hand side. To its right, the overview area represents the study's structure, in that the items therein are run sequentially from top to bottom.An experiment is built by dragging and dropping items from the toolbar into the overview area.Sequences can be used to run a number of items in succession. In addition, loop items can be used to repeatedly run sequences with some degree of variation, for example, trials with varying stimuli (Figure 1, right panel).