This visualization displays four variables (or dimensions) with a two dimensional plot. The scatterplot displays reaction time (RT) differences between cochlear implant users and normal hearing participants in a lexical decision task. During lexical decision participants judge whether a sound stimulus they hear is a word or not (like `trud' in English).
The four dimensions are differences in RT (1) displayed as a function of neighborhood density (2) and word frequency (3). The size of the dot reflects the size of the difference in RT. The colors of the dots distinguish words (blue) and non-words (orange) (4). The plot is interactive. Hovering the mouse on a dots displays the name of the (non-)word, the size of the difference in milliseconds (ms), the neighborhood density and frequency (log-scaled).
This post describes in detail the creation of the scatterplot.