When I teach data visualization, I love showing my students how simple changes in the way one visualizes his or her data may drive the potential audience to different conclusions. When done correctly, such changes can help the presenters making their point. They also can be used to mislead the audience. I keep reminding the students that it is up to them to keep their visualizations honest and fair. In his recent post, Robert Kosara, the owner of https://eagereyes.org/, mentioned another possible way that may change the perceived conclusion. This time, not by changing a graph but by changing the order of graphs exposed to a person. Citing Robert Kosara:
Priming is when what you see first influences how you perceive what comes next. In a series of studies, [André Calero Valdez, Martina Ziefle, and Michael Sedlmair] showed that these effects also exist in the particular case of scatterplots that show separable or non-separable clusters. Seeing one kind of plot first changes the likelihood of you judging a subsequent plot as the same or another type.
As any tool, priming can be used for good or bad causes. Priming abuse can be a deliberate exposure to non-relevant information in order to manipulate the audience. A good way to use priming is to educate the listeners of its effect, and repeatedly exposing them to alternate contexts. Alternatively, reminding the audience of the “before” graph, before showing them the similar “after” situation will also create a plausible effect of context setting.
P.S. The paper mentioned by Kosara is noticeable not only by its results (they are not as astonishing as I expected from the featured image) but also by how the authors report their research, including the failures.
Featured image is Figure 1 from Calero Valdez et al. Priming and Anchoring Effects in Visualization